Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Thu, 18 Jan 2018 19:24:52 +
Jean-Philippe Brucker  wrote:

> Hi Jacob,
> 
> I've got minor comments after working with this patch, sorry for the
> multiple replies
> 
> On 17/11/17 18:55, Jacob Pan wrote:
> [...]
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 829e9e9..97b7990 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > *group, struct device *dev) goto err_free_name;
> > }
> >  
> > +   dev->iommu_param = kzalloc(sizeof(struct
> > iommu_fault_param), GFP_KERNEL);  
> 
> This should be "sizeof(struct iommu_param)" or maybe
> "sizeof(*dev->iommu_param)".
> 
good catch, thanks,
> > +   if (!dev->iommu_param) {
> > +   ret = -ENOMEM;
> > +   goto err_free_name;
> > +   }
> > +
> > kobject_get(group->devices_kobj);
> >  
> > dev->iommu_group = group;
> > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > *dev) sysfs_remove_link(>kobj, "iommu_group");
> >  
> > trace_remove_device_from_group(group->id, dev);
> > -
> > +   kfree(dev->iommu_param);
> > kfree(device->name);
> > kfree(device);
> > dev->iommu_group = NULL;
> > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > iommu_group *group, }
> >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> > 
> > +int iommu_register_device_fault_handler(struct device *dev,
> > +   iommu_dev_fault_handler_t
> > handler,
> > +   void *data)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   /*
> > +* Device iommu_param should have been allocated when
> > device is
> > +* added to its iommu_group.
> > +*/
> > +   if (!idata)
> > +   return -EINVAL;
> > +   /* Only allow one fault handler registered for each device
> > */
> > +   if (idata->fault_param)
> > +   return -EBUSY;
> > +   get_device(dev);
> > +   idata->fault_param =
> > +   kzalloc(sizeof(struct iommu_fault_param),
> > GFP_KERNEL);
> > +   if (!idata->fault_param)
> > +   return -ENOMEM;
> > +   idata->fault_param->handler = handler;
> > +   idata->fault_param->data = data;
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > +
> > +int iommu_unregister_device_fault_handler(struct device *dev)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   if (!idata)
> > +   return -EINVAL;
> > +
> > +   kfree(idata->fault_param);
> > +   idata->fault_param = NULL;
> > +   put_device(dev);
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);  
> 
> We should probably document register() and unregister() functions
> since they are part of the device driver API. If it helps I came up
> with:
> 
> /**
>  * iommu_register_device_fault_handler() - Register a device fault
> handler
>  * @dev: the device
>  * @handler: the fault handler
>  * @data: private data passed as argument to the handler
>  *
>  * When an IOMMU fault event is received, call this handler with the
> fault event
>  * and data as argument. The handler should return 0. If the fault is
>  * recoverable (IOMMU_FAULT_PAGE_REQ), the handler must also complete
>  * the fault by calling iommu_page_response() with one of the
> following
>  * response code:
>  * - IOMMU_PAGE_RESP_SUCCESS: retry the translation
>  * - IOMMU_PAGE_RESP_INVALID: terminate the fault
>  * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
>  *   page faults if possible.
>  *
>  * Return 0 if the fault handler was installed successfully, or an
> error. */
> 
> /**
>  * iommu_unregister_device_fault_handler() - Unregister the device
> fault handler
>  * @dev: the device
>  *
>  * Remove the device fault handler installed with
>  * iommu_register_device_fault_handler().
>  *
>  * Return 0 on success, or an error.
>  */
> 
agreed. thanks. sorry about the delay.
> Thanks,
> Jean

[Jacob Pan]

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Thu, 18 Jan 2018 19:24:52 +
Jean-Philippe Brucker  wrote:

> Hi Jacob,
> 
> I've got minor comments after working with this patch, sorry for the
> multiple replies
> 
> On 17/11/17 18:55, Jacob Pan wrote:
> [...]
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 829e9e9..97b7990 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > *group, struct device *dev) goto err_free_name;
> > }
> >  
> > +   dev->iommu_param = kzalloc(sizeof(struct
> > iommu_fault_param), GFP_KERNEL);  
> 
> This should be "sizeof(struct iommu_param)" or maybe
> "sizeof(*dev->iommu_param)".
> 
good catch, thanks,
> > +   if (!dev->iommu_param) {
> > +   ret = -ENOMEM;
> > +   goto err_free_name;
> > +   }
> > +
> > kobject_get(group->devices_kobj);
> >  
> > dev->iommu_group = group;
> > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > *dev) sysfs_remove_link(>kobj, "iommu_group");
> >  
> > trace_remove_device_from_group(group->id, dev);
> > -
> > +   kfree(dev->iommu_param);
> > kfree(device->name);
> > kfree(device);
> > dev->iommu_group = NULL;
> > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > iommu_group *group, }
> >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> > 
> > +int iommu_register_device_fault_handler(struct device *dev,
> > +   iommu_dev_fault_handler_t
> > handler,
> > +   void *data)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   /*
> > +* Device iommu_param should have been allocated when
> > device is
> > +* added to its iommu_group.
> > +*/
> > +   if (!idata)
> > +   return -EINVAL;
> > +   /* Only allow one fault handler registered for each device
> > */
> > +   if (idata->fault_param)
> > +   return -EBUSY;
> > +   get_device(dev);
> > +   idata->fault_param =
> > +   kzalloc(sizeof(struct iommu_fault_param),
> > GFP_KERNEL);
> > +   if (!idata->fault_param)
> > +   return -ENOMEM;
> > +   idata->fault_param->handler = handler;
> > +   idata->fault_param->data = data;
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > +
> > +int iommu_unregister_device_fault_handler(struct device *dev)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   if (!idata)
> > +   return -EINVAL;
> > +
> > +   kfree(idata->fault_param);
> > +   idata->fault_param = NULL;
> > +   put_device(dev);
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);  
> 
> We should probably document register() and unregister() functions
> since they are part of the device driver API. If it helps I came up
> with:
> 
> /**
>  * iommu_register_device_fault_handler() - Register a device fault
> handler
>  * @dev: the device
>  * @handler: the fault handler
>  * @data: private data passed as argument to the handler
>  *
>  * When an IOMMU fault event is received, call this handler with the
> fault event
>  * and data as argument. The handler should return 0. If the fault is
>  * recoverable (IOMMU_FAULT_PAGE_REQ), the handler must also complete
>  * the fault by calling iommu_page_response() with one of the
> following
>  * response code:
>  * - IOMMU_PAGE_RESP_SUCCESS: retry the translation
>  * - IOMMU_PAGE_RESP_INVALID: terminate the fault
>  * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
>  *   page faults if possible.
>  *
>  * Return 0 if the fault handler was installed successfully, or an
> error. */
> 
> /**
>  * iommu_unregister_device_fault_handler() - Unregister the device
> fault handler
>  * @dev: the device
>  *
>  * Remove the device fault handler installed with
>  * iommu_register_device_fault_handler().
>  *
>  * Return 0 on success, or an error.
>  */
> 
agreed. thanks. sorry about the delay.
> Thanks,
> Jean

[Jacob Pan]

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jean-Philippe Brucker]

Hi Jacob,

I've got minor comments after working with this patch, sorry for the
multiple replies

On 17/11/17 18:55, Jacob Pan wrote:
[...]
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);

This should be "sizeof(struct iommu_param)" or maybe
"sizeof(*dev->iommu_param)".

> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> 
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);

We should probably document register() and unregister() functions since
they are part of the device driver API. If it helps I came up with:

/**
 * iommu_register_device_fault_handler() - Register a device fault handler
 * @dev: the device
 * @handler: the fault handler
 * @data: private data passed as argument to the handler
 *
 * When an IOMMU fault event is received, call this handler with the fault event
 * and data as argument. The handler should return 0. If the fault is
 * recoverable (IOMMU_FAULT_PAGE_REQ), the handler must also complete
 * the fault by calling iommu_page_response() with one of the following
 * response code:
 * - IOMMU_PAGE_RESP_SUCCESS: retry the translation
 * - IOMMU_PAGE_RESP_INVALID: terminate the fault
 * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
 *   page faults if possible.
 *
 * Return 0 if the fault handler was installed successfully, or an error.
 */

/**
 * iommu_unregister_device_fault_handler() - Unregister the device fault handler
 * @dev: the device
 *
 * Remove the device fault handler installed with
 * iommu_register_device_fault_handler().
 *
 * Return 0 on success, or an error.
 */

Thanks,
Jean

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jean-Philippe Brucker]

Hi Jacob,

I've got minor comments after working with this patch, sorry for the
multiple replies

On 17/11/17 18:55, Jacob Pan wrote:
[...]
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);

This should be "sizeof(struct iommu_param)" or maybe
"sizeof(*dev->iommu_param)".

> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> 
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);

We should probably document register() and unregister() functions since
they are part of the device driver API. If it helps I came up with:

/**
 * iommu_register_device_fault_handler() - Register a device fault handler
 * @dev: the device
 * @handler: the fault handler
 * @data: private data passed as argument to the handler
 *
 * When an IOMMU fault event is received, call this handler with the fault event
 * and data as argument. The handler should return 0. If the fault is
 * recoverable (IOMMU_FAULT_PAGE_REQ), the handler must also complete
 * the fault by calling iommu_page_response() with one of the following
 * response code:
 * - IOMMU_PAGE_RESP_SUCCESS: retry the translation
 * - IOMMU_PAGE_RESP_INVALID: terminate the fault
 * - IOMMU_PAGE_RESP_FAILURE: terminate the fault and stop reporting
 *   page faults if possible.
 *
 * Return 0 if the fault handler was installed successfully, or an error.
 */

/**
 * iommu_unregister_device_fault_handler() - Unregister the device fault handler
 * @dev: the device
 *
 * Remove the device fault handler installed with
 * iommu_register_device_fault_handler().
 *
 * Return 0 on success, or an error.
 */

Thanks,
Jean

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jean-Philippe Brucker]

On 17/11/17 18:55, Jacob Pan wrote:
[...]
> +static inline int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t 
> handler,
> + void *data)
> +{
> + return 0;> +}
> +
> +static inline int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + return 0;
> +}
> +
> +static inline bool iommu_has_device_fault_handler(struct device *dev)
> +{
> + return false;
> +}
> +
> +static inline int iommu_report_device_fault(struct device *dev, struct 
> iommu_fault_event *evt)
> +{
> + return 0;
> +}

Not too important but these stubs, when CONFIG_IOMMU_API is disabled,
usually return an error value (-ENODEV) instead of 0.

Thanks,
Jean

> +
>  static inline int iommu_group_id(struct iommu_group *group)
>  {
>   return -ENODEV;
> 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jean-Philippe Brucker]

On 17/11/17 18:55, Jacob Pan wrote:
[...]
> +static inline int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t 
> handler,
> + void *data)
> +{
> + return 0;> +}
> +
> +static inline int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + return 0;
> +}
> +
> +static inline bool iommu_has_device_fault_handler(struct device *dev)
> +{
> + return false;
> +}
> +
> +static inline int iommu_report_device_fault(struct device *dev, struct 
> iommu_fault_event *evt)
> +{
> + return 0;
> +}

Not too important but these stubs, when CONFIG_IOMMU_API is disabled,
usually return an error value (-ENODEV) instead of 0.

Thanks,
Jean

> +
>  static inline int iommu_group_id(struct iommu_group *group)
>  {
>   return -ENODEV;
> 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Fri, 8 Dec 2017 13:59:09 -0700
Alex Williamson  wrote:

> > > 
> > > Isn't this all rather racy?  I see that we can have multiple
> > > callers to register racing.
> > I agree, should use a lock here to prevent unregister. For multiple
> > caller race, it won't happen since there is only one caller can
> > register handler.  
> 
> If you have multiple simultaneous callers to
> iommu_register_device_fault_handler, they can all get past the test
> for fault_param (testing and setting is not atomic), then it's
> indeterminate which handler gets installed.  Thanks,
> 
I see, having the mutex would prevent it. Later callers would get
-EBUSY.
Thanks a lot!
> Alex

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Fri, 8 Dec 2017 13:59:09 -0700
Alex Williamson  wrote:

> > > 
> > > Isn't this all rather racy?  I see that we can have multiple
> > > callers to register racing.
> > I agree, should use a lock here to prevent unregister. For multiple
> > caller race, it won't happen since there is only one caller can
> > register handler.  
> 
> If you have multiple simultaneous callers to
> iommu_register_device_fault_handler, they can all get past the test
> for fault_param (testing and setting is not atomic), then it's
> indeterminate which handler gets installed.  Thanks,
> 
I see, having the mutex would prevent it. Later callers would get
-EBUSY.
Thanks a lot!
> Alex

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Tue, 5 Dec 2017 14:22:41 +0800
Lu Baolu  wrote:

> > +int iommu_report_device_fault(struct device *dev, struct
> > iommu_fault_event *evt) +{
> > +   /* we only report device fault if there is a handler
> > registered */
> > +   if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> > +   !dev->iommu_param->fault_param->handler)  
> 
> Can this replaced by:
> 
> if (!iommu_has_device_fault_handler(dev))
> 
right, and under a lock too.

Thanks,

Jacob

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Tue, 5 Dec 2017 14:22:41 +0800
Lu Baolu  wrote:

> > +int iommu_report_device_fault(struct device *dev, struct
> > iommu_fault_event *evt) +{
> > +   /* we only report device fault if there is a handler
> > registered */
> > +   if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> > +   !dev->iommu_param->fault_param->handler)  
> 
> Can this replaced by:
> 
> if (!iommu_has_device_fault_handler(dev))
> 
right, and under a lock too.

Thanks,

Jacob

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Alex Williamson]

On Fri, 8 Dec 2017 12:23:58 -0800
Jacob Pan  wrote:

> On Thu, 7 Dec 2017 14:27:25 -0700
> Alex Williamson  wrote:
> 
> > On Fri, 17 Nov 2017 10:55:08 -0800
> > Jacob Pan  wrote:
> >   
> > > Traditionally, device specific faults are detected and handled
> > > within their own device drivers. When IOMMU is enabled, faults such
> > > as DMA related transactions are detected by IOMMU. There is no
> > > generic reporting mechanism to report faults back to the in-kernel
> > > device driver or the guest OS in case of assigned devices.
> > > 
> > > Faults detected by IOMMU is based on the transaction's source ID
> > > which can be reported at per device basis, regardless of the device
> > > type is a PCI device or not.
> > > 
> > > The fault types include recoverable (e.g. page request) and
> > > unrecoverable faults(e.g. access error). In most cases, faults can
> > > be handled by IOMMU drivers internally. The primary use cases are as
> > > follows:
> > > 1. page request fault originated from an SVM capable device that is
> > > assigned to guest via vIOMMU. In this case, the first level page
> > > tables are owned by the guest. Page request must be propagated to
> > > the guest to let guest OS fault in the pages then send page
> > > response. In this mechanism, the direct receiver of IOMMU fault
> > > notification is VFIO, which can relay notification events to QEMU
> > > or other user space software.
> > > 
> > > 2. faults need more subtle handling by device drivers. Other than
> > > simply invoke reset function, there are needs to let device driver
> > > handle the fault with a smaller impact.
> > > 
> > > This patchset is intended to create a generic fault report API such
> > > that it can scale as follows:
> > > - all IOMMU types
> > > - PCI and non-PCI devices
> > > - recoverable and unrecoverable faults
> > > - VFIO and other other in kernel users
> > > - DMA & IRQ remapping (TBD)
> > > The original idea was brought up by David Woodhouse and discussions
> > > summarized at https://lwn.net/Articles/608914/.
> > > 
> > > Signed-off-by: Jacob Pan 
> > > Signed-off-by: Ashok Raj 
> > > ---
> > >  drivers/iommu/iommu.c | 63
> > > ++-
> > > include/linux/iommu.h | 36 + 2 files
> > > changed, 98 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > > index 829e9e9..97b7990 100644
> > > --- a/drivers/iommu/iommu.c
> > > +++ b/drivers/iommu/iommu.c
> > > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > > *group, struct device *dev) goto err_free_name;
> > >   }
> > >  
> > > + dev->iommu_param = kzalloc(sizeof(struct
> > > iommu_fault_param), GFP_KERNEL);
> > > + if (!dev->iommu_param) {
> > > + ret = -ENOMEM;
> > > + goto err_free_name;
> > > + }
> > > +
> > >   kobject_get(group->devices_kobj);
> > >  
> > >   dev->iommu_group = group;
> > > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > > *dev) sysfs_remove_link(>kobj, "iommu_group");
> > >  
> > >   trace_remove_device_from_group(group->id, dev);
> > > -
> > > + kfree(dev->iommu_param);
> > >   kfree(device->name);
> > >   kfree(device);
> > >   dev->iommu_group = NULL;
> > > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > > iommu_group *group, }
> > >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> > >  
> > > +int iommu_register_device_fault_handler(struct device *dev,
> > > + iommu_dev_fault_handler_t
> > > handler,
> > > + void *data)
> > > +{
> > > + struct iommu_param *idata = dev->iommu_param;
> > > +
> > > + /*
> > > +  * Device iommu_param should have been allocated when
> > > device is
> > > +  * added to its iommu_group.
> > > +  */
> > > + if (!idata)
> > > + return -EINVAL;
> > > + /* Only allow one fault handler registered for each device
> > > */
> > > + if (idata->fault_param)
> > > + return -EBUSY;
> > > + get_device(dev);
> > > + idata->fault_param =
> > > + kzalloc(sizeof(struct iommu_fault_param),
> > > GFP_KERNEL);
> > > + if (!idata->fault_param)
> > > + return -ENOMEM;
> > > + idata->fault_param->handler = handler;
> > > + idata->fault_param->data = data;
> > > +
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > > +
> > > +int iommu_unregister_device_fault_handler(struct device *dev)
> > > +{
> > > + struct iommu_param *idata = dev->iommu_param;
> > > +
> > > + if (!idata)
> > > + return -EINVAL;
> > > +
> > > + kfree(idata->fault_param);
> > > + idata->fault_param = NULL;
> > > + put_device(dev);
> > > +
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> > > +
> > > +
> > > +int 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Alex Williamson]

On Fri, 8 Dec 2017 12:23:58 -0800
Jacob Pan  wrote:

> On Thu, 7 Dec 2017 14:27:25 -0700
> Alex Williamson  wrote:
> 
> > On Fri, 17 Nov 2017 10:55:08 -0800
> > Jacob Pan  wrote:
> >   
> > > Traditionally, device specific faults are detected and handled
> > > within their own device drivers. When IOMMU is enabled, faults such
> > > as DMA related transactions are detected by IOMMU. There is no
> > > generic reporting mechanism to report faults back to the in-kernel
> > > device driver or the guest OS in case of assigned devices.
> > > 
> > > Faults detected by IOMMU is based on the transaction's source ID
> > > which can be reported at per device basis, regardless of the device
> > > type is a PCI device or not.
> > > 
> > > The fault types include recoverable (e.g. page request) and
> > > unrecoverable faults(e.g. access error). In most cases, faults can
> > > be handled by IOMMU drivers internally. The primary use cases are as
> > > follows:
> > > 1. page request fault originated from an SVM capable device that is
> > > assigned to guest via vIOMMU. In this case, the first level page
> > > tables are owned by the guest. Page request must be propagated to
> > > the guest to let guest OS fault in the pages then send page
> > > response. In this mechanism, the direct receiver of IOMMU fault
> > > notification is VFIO, which can relay notification events to QEMU
> > > or other user space software.
> > > 
> > > 2. faults need more subtle handling by device drivers. Other than
> > > simply invoke reset function, there are needs to let device driver
> > > handle the fault with a smaller impact.
> > > 
> > > This patchset is intended to create a generic fault report API such
> > > that it can scale as follows:
> > > - all IOMMU types
> > > - PCI and non-PCI devices
> > > - recoverable and unrecoverable faults
> > > - VFIO and other other in kernel users
> > > - DMA & IRQ remapping (TBD)
> > > The original idea was brought up by David Woodhouse and discussions
> > > summarized at https://lwn.net/Articles/608914/.
> > > 
> > > Signed-off-by: Jacob Pan 
> > > Signed-off-by: Ashok Raj 
> > > ---
> > >  drivers/iommu/iommu.c | 63
> > > ++-
> > > include/linux/iommu.h | 36 + 2 files
> > > changed, 98 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > > index 829e9e9..97b7990 100644
> > > --- a/drivers/iommu/iommu.c
> > > +++ b/drivers/iommu/iommu.c
> > > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > > *group, struct device *dev) goto err_free_name;
> > >   }
> > >  
> > > + dev->iommu_param = kzalloc(sizeof(struct
> > > iommu_fault_param), GFP_KERNEL);
> > > + if (!dev->iommu_param) {
> > > + ret = -ENOMEM;
> > > + goto err_free_name;
> > > + }
> > > +
> > >   kobject_get(group->devices_kobj);
> > >  
> > >   dev->iommu_group = group;
> > > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > > *dev) sysfs_remove_link(>kobj, "iommu_group");
> > >  
> > >   trace_remove_device_from_group(group->id, dev);
> > > -
> > > + kfree(dev->iommu_param);
> > >   kfree(device->name);
> > >   kfree(device);
> > >   dev->iommu_group = NULL;
> > > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > > iommu_group *group, }
> > >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> > >  
> > > +int iommu_register_device_fault_handler(struct device *dev,
> > > + iommu_dev_fault_handler_t
> > > handler,
> > > + void *data)
> > > +{
> > > + struct iommu_param *idata = dev->iommu_param;
> > > +
> > > + /*
> > > +  * Device iommu_param should have been allocated when
> > > device is
> > > +  * added to its iommu_group.
> > > +  */
> > > + if (!idata)
> > > + return -EINVAL;
> > > + /* Only allow one fault handler registered for each device
> > > */
> > > + if (idata->fault_param)
> > > + return -EBUSY;
> > > + get_device(dev);
> > > + idata->fault_param =
> > > + kzalloc(sizeof(struct iommu_fault_param),
> > > GFP_KERNEL);
> > > + if (!idata->fault_param)
> > > + return -ENOMEM;
> > > + idata->fault_param->handler = handler;
> > > + idata->fault_param->data = data;
> > > +
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > > +
> > > +int iommu_unregister_device_fault_handler(struct device *dev)
> > > +{
> > > + struct iommu_param *idata = dev->iommu_param;
> > > +
> > > + if (!idata)
> > > + return -EINVAL;
> > > +
> > > + kfree(idata->fault_param);
> > > + idata->fault_param = NULL;
> > > + put_device(dev);
> > > +
> > > + return 0;
> > > +}
> > > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> > > +
> > > +
> > > +int iommu_report_device_fault(struct device *dev, struct
> > > iommu_fault_event *evt) +{
> > > + /* we only report device fault if there is a handler
> > > 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Thu, 7 Dec 2017 14:27:25 -0700
Alex Williamson  wrote:

> On Fri, 17 Nov 2017 10:55:08 -0800
> Jacob Pan  wrote:
> 
> > Traditionally, device specific faults are detected and handled
> > within their own device drivers. When IOMMU is enabled, faults such
> > as DMA related transactions are detected by IOMMU. There is no
> > generic reporting mechanism to report faults back to the in-kernel
> > device driver or the guest OS in case of assigned devices.
> > 
> > Faults detected by IOMMU is based on the transaction's source ID
> > which can be reported at per device basis, regardless of the device
> > type is a PCI device or not.
> > 
> > The fault types include recoverable (e.g. page request) and
> > unrecoverable faults(e.g. access error). In most cases, faults can
> > be handled by IOMMU drivers internally. The primary use cases are as
> > follows:
> > 1. page request fault originated from an SVM capable device that is
> > assigned to guest via vIOMMU. In this case, the first level page
> > tables are owned by the guest. Page request must be propagated to
> > the guest to let guest OS fault in the pages then send page
> > response. In this mechanism, the direct receiver of IOMMU fault
> > notification is VFIO, which can relay notification events to QEMU
> > or other user space software.
> > 
> > 2. faults need more subtle handling by device drivers. Other than
> > simply invoke reset function, there are needs to let device driver
> > handle the fault with a smaller impact.
> > 
> > This patchset is intended to create a generic fault report API such
> > that it can scale as follows:
> > - all IOMMU types
> > - PCI and non-PCI devices
> > - recoverable and unrecoverable faults
> > - VFIO and other other in kernel users
> > - DMA & IRQ remapping (TBD)
> > The original idea was brought up by David Woodhouse and discussions
> > summarized at https://lwn.net/Articles/608914/.
> > 
> > Signed-off-by: Jacob Pan 
> > Signed-off-by: Ashok Raj 
> > ---
> >  drivers/iommu/iommu.c | 63
> > ++-
> > include/linux/iommu.h | 36 + 2 files
> > changed, 98 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 829e9e9..97b7990 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > *group, struct device *dev) goto err_free_name;
> > }
> >  
> > +   dev->iommu_param = kzalloc(sizeof(struct
> > iommu_fault_param), GFP_KERNEL);
> > +   if (!dev->iommu_param) {
> > +   ret = -ENOMEM;
> > +   goto err_free_name;
> > +   }
> > +
> > kobject_get(group->devices_kobj);
> >  
> > dev->iommu_group = group;
> > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > *dev) sysfs_remove_link(>kobj, "iommu_group");
> >  
> > trace_remove_device_from_group(group->id, dev);
> > -
> > +   kfree(dev->iommu_param);
> > kfree(device->name);
> > kfree(device);
> > dev->iommu_group = NULL;
> > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > iommu_group *group, }
> >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> >  
> > +int iommu_register_device_fault_handler(struct device *dev,
> > +   iommu_dev_fault_handler_t
> > handler,
> > +   void *data)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   /*
> > +* Device iommu_param should have been allocated when
> > device is
> > +* added to its iommu_group.
> > +*/
> > +   if (!idata)
> > +   return -EINVAL;
> > +   /* Only allow one fault handler registered for each device
> > */
> > +   if (idata->fault_param)
> > +   return -EBUSY;
> > +   get_device(dev);
> > +   idata->fault_param =
> > +   kzalloc(sizeof(struct iommu_fault_param),
> > GFP_KERNEL);
> > +   if (!idata->fault_param)
> > +   return -ENOMEM;
> > +   idata->fault_param->handler = handler;
> > +   idata->fault_param->data = data;
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > +
> > +int iommu_unregister_device_fault_handler(struct device *dev)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   if (!idata)
> > +   return -EINVAL;
> > +
> > +   kfree(idata->fault_param);
> > +   idata->fault_param = NULL;
> > +   put_device(dev);
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> > +
> > +
> > +int iommu_report_device_fault(struct device *dev, struct
> > iommu_fault_event *evt) +{
> > +   /* we only report device fault if there is a handler
> > registered */
> > +   if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> > +   

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Jacob Pan]

On Thu, 7 Dec 2017 14:27:25 -0700
Alex Williamson  wrote:

> On Fri, 17 Nov 2017 10:55:08 -0800
> Jacob Pan  wrote:
> 
> > Traditionally, device specific faults are detected and handled
> > within their own device drivers. When IOMMU is enabled, faults such
> > as DMA related transactions are detected by IOMMU. There is no
> > generic reporting mechanism to report faults back to the in-kernel
> > device driver or the guest OS in case of assigned devices.
> > 
> > Faults detected by IOMMU is based on the transaction's source ID
> > which can be reported at per device basis, regardless of the device
> > type is a PCI device or not.
> > 
> > The fault types include recoverable (e.g. page request) and
> > unrecoverable faults(e.g. access error). In most cases, faults can
> > be handled by IOMMU drivers internally. The primary use cases are as
> > follows:
> > 1. page request fault originated from an SVM capable device that is
> > assigned to guest via vIOMMU. In this case, the first level page
> > tables are owned by the guest. Page request must be propagated to
> > the guest to let guest OS fault in the pages then send page
> > response. In this mechanism, the direct receiver of IOMMU fault
> > notification is VFIO, which can relay notification events to QEMU
> > or other user space software.
> > 
> > 2. faults need more subtle handling by device drivers. Other than
> > simply invoke reset function, there are needs to let device driver
> > handle the fault with a smaller impact.
> > 
> > This patchset is intended to create a generic fault report API such
> > that it can scale as follows:
> > - all IOMMU types
> > - PCI and non-PCI devices
> > - recoverable and unrecoverable faults
> > - VFIO and other other in kernel users
> > - DMA & IRQ remapping (TBD)
> > The original idea was brought up by David Woodhouse and discussions
> > summarized at https://lwn.net/Articles/608914/.
> > 
> > Signed-off-by: Jacob Pan 
> > Signed-off-by: Ashok Raj 
> > ---
> >  drivers/iommu/iommu.c | 63
> > ++-
> > include/linux/iommu.h | 36 + 2 files
> > changed, 98 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> > index 829e9e9..97b7990 100644
> > --- a/drivers/iommu/iommu.c
> > +++ b/drivers/iommu/iommu.c
> > @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group
> > *group, struct device *dev) goto err_free_name;
> > }
> >  
> > +   dev->iommu_param = kzalloc(sizeof(struct
> > iommu_fault_param), GFP_KERNEL);
> > +   if (!dev->iommu_param) {
> > +   ret = -ENOMEM;
> > +   goto err_free_name;
> > +   }
> > +
> > kobject_get(group->devices_kobj);
> >  
> > dev->iommu_group = group;
> > @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device
> > *dev) sysfs_remove_link(>kobj, "iommu_group");
> >  
> > trace_remove_device_from_group(group->id, dev);
> > -
> > +   kfree(dev->iommu_param);
> > kfree(device->name);
> > kfree(device);
> > dev->iommu_group = NULL;
> > @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct
> > iommu_group *group, }
> >  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
> >  
> > +int iommu_register_device_fault_handler(struct device *dev,
> > +   iommu_dev_fault_handler_t
> > handler,
> > +   void *data)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   /*
> > +* Device iommu_param should have been allocated when
> > device is
> > +* added to its iommu_group.
> > +*/
> > +   if (!idata)
> > +   return -EINVAL;
> > +   /* Only allow one fault handler registered for each device
> > */
> > +   if (idata->fault_param)
> > +   return -EBUSY;
> > +   get_device(dev);
> > +   idata->fault_param =
> > +   kzalloc(sizeof(struct iommu_fault_param),
> > GFP_KERNEL);
> > +   if (!idata->fault_param)
> > +   return -ENOMEM;
> > +   idata->fault_param->handler = handler;
> > +   idata->fault_param->data = data;
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> > +
> > +int iommu_unregister_device_fault_handler(struct device *dev)
> > +{
> > +   struct iommu_param *idata = dev->iommu_param;
> > +
> > +   if (!idata)
> > +   return -EINVAL;
> > +
> > +   kfree(idata->fault_param);
> > +   idata->fault_param = NULL;
> > +   put_device(dev);
> > +
> > +   return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> > +
> > +
> > +int iommu_report_device_fault(struct device *dev, struct
> > iommu_fault_event *evt) +{
> > +   /* we only report device fault if there is a handler
> > registered */
> > +   if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> > +   !dev->iommu_param->fault_param->handler)
> > +   return -ENOSYS;
> > +
> > +   return dev->iommu_param->fault_param->handler(evt,
> > +
> > 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Alex Williamson]

On Fri, 17 Nov 2017 10:55:08 -0800
Jacob Pan  wrote:

> Traditionally, device specific faults are detected and handled within
> their own device drivers. When IOMMU is enabled, faults such as DMA
> related transactions are detected by IOMMU. There is no generic
> reporting mechanism to report faults back to the in-kernel device
> driver or the guest OS in case of assigned devices.
> 
> Faults detected by IOMMU is based on the transaction's source ID which
> can be reported at per device basis, regardless of the device type is a
> PCI device or not.
> 
> The fault types include recoverable (e.g. page request) and
> unrecoverable faults(e.g. access error). In most cases, faults can be
> handled by IOMMU drivers internally. The primary use cases are as
> follows:
> 1. page request fault originated from an SVM capable device that is
> assigned to guest via vIOMMU. In this case, the first level page tables
> are owned by the guest. Page request must be propagated to the guest to
> let guest OS fault in the pages then send page response. In this
> mechanism, the direct receiver of IOMMU fault notification is VFIO,
> which can relay notification events to QEMU or other user space
> software.
> 
> 2. faults need more subtle handling by device drivers. Other than
> simply invoke reset function, there are needs to let device driver
> handle the fault with a smaller impact.
> 
> This patchset is intended to create a generic fault report API such
> that it can scale as follows:
> - all IOMMU types
> - PCI and non-PCI devices
> - recoverable and unrecoverable faults
> - VFIO and other other in kernel users
> - DMA & IRQ remapping (TBD)
> The original idea was brought up by David Woodhouse and discussions
> summarized at https://lwn.net/Articles/608914/.
> 
> Signed-off-by: Jacob Pan 
> Signed-off-by: Ashok Raj 
> ---
>  drivers/iommu/iommu.c | 63 
> ++-
>  include/linux/iommu.h | 36 +
>  2 files changed, 98 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);
> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
>  
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> +
> +
> +int iommu_report_device_fault(struct device *dev, struct iommu_fault_event 
> *evt)
> +{
> + /* we only report device fault if there is a handler registered */
> + if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> + !dev->iommu_param->fault_param->handler)
> + return -ENOSYS;
> +
> + return dev->iommu_param->fault_param->handler(evt,
> + 
> dev->iommu_param->fault_param->data);
> +}
> 

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Alex Williamson]

On Fri, 17 Nov 2017 10:55:08 -0800
Jacob Pan  wrote:

> Traditionally, device specific faults are detected and handled within
> their own device drivers. When IOMMU is enabled, faults such as DMA
> related transactions are detected by IOMMU. There is no generic
> reporting mechanism to report faults back to the in-kernel device
> driver or the guest OS in case of assigned devices.
> 
> Faults detected by IOMMU is based on the transaction's source ID which
> can be reported at per device basis, regardless of the device type is a
> PCI device or not.
> 
> The fault types include recoverable (e.g. page request) and
> unrecoverable faults(e.g. access error). In most cases, faults can be
> handled by IOMMU drivers internally. The primary use cases are as
> follows:
> 1. page request fault originated from an SVM capable device that is
> assigned to guest via vIOMMU. In this case, the first level page tables
> are owned by the guest. Page request must be propagated to the guest to
> let guest OS fault in the pages then send page response. In this
> mechanism, the direct receiver of IOMMU fault notification is VFIO,
> which can relay notification events to QEMU or other user space
> software.
> 
> 2. faults need more subtle handling by device drivers. Other than
> simply invoke reset function, there are needs to let device driver
> handle the fault with a smaller impact.
> 
> This patchset is intended to create a generic fault report API such
> that it can scale as follows:
> - all IOMMU types
> - PCI and non-PCI devices
> - recoverable and unrecoverable faults
> - VFIO and other other in kernel users
> - DMA & IRQ remapping (TBD)
> The original idea was brought up by David Woodhouse and discussions
> summarized at https://lwn.net/Articles/608914/.
> 
> Signed-off-by: Jacob Pan 
> Signed-off-by: Ashok Raj 
> ---
>  drivers/iommu/iommu.c | 63 
> ++-
>  include/linux/iommu.h | 36 +
>  2 files changed, 98 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);
> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
>  
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> +
> +
> +int iommu_report_device_fault(struct device *dev, struct iommu_fault_event 
> *evt)
> +{
> + /* we only report device fault if there is a handler registered */
> + if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> + !dev->iommu_param->fault_param->handler)
> + return -ENOSYS;
> +
> + return dev->iommu_param->fault_param->handler(evt,
> + 
> dev->iommu_param->fault_param->data);
> +}
> +EXPORT_SYMBOL_GPL(iommu_report_device_fault);
> +

Isn't this all rather racy?  I see that we can have multiple callers to

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Lu Baolu]

Hi,

On 11/18/2017 02:55 AM, Jacob Pan wrote:
> Traditionally, device specific faults are detected and handled within
> their own device drivers. When IOMMU is enabled, faults such as DMA
> related transactions are detected by IOMMU. There is no generic
> reporting mechanism to report faults back to the in-kernel device
> driver or the guest OS in case of assigned devices.
>
> Faults detected by IOMMU is based on the transaction's source ID which
> can be reported at per device basis, regardless of the device type is a
> PCI device or not.
>
> The fault types include recoverable (e.g. page request) and
> unrecoverable faults(e.g. access error). In most cases, faults can be
> handled by IOMMU drivers internally. The primary use cases are as
> follows:
> 1. page request fault originated from an SVM capable device that is
> assigned to guest via vIOMMU. In this case, the first level page tables
> are owned by the guest. Page request must be propagated to the guest to
> let guest OS fault in the pages then send page response. In this
> mechanism, the direct receiver of IOMMU fault notification is VFIO,
> which can relay notification events to QEMU or other user space
> software.
>
> 2. faults need more subtle handling by device drivers. Other than
> simply invoke reset function, there are needs to let device driver
> handle the fault with a smaller impact.
>
> This patchset is intended to create a generic fault report API such
> that it can scale as follows:
> - all IOMMU types
> - PCI and non-PCI devices
> - recoverable and unrecoverable faults
> - VFIO and other other in kernel users
> - DMA & IRQ remapping (TBD)
> The original idea was brought up by David Woodhouse and discussions
> summarized at https://lwn.net/Articles/608914/.
>
> Signed-off-by: Jacob Pan 
> Signed-off-by: Ashok Raj 
> ---
>  drivers/iommu/iommu.c | 63 
> ++-
>  include/linux/iommu.h | 36 +
>  2 files changed, 98 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);
> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
>  
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> +
> +
> +int iommu_report_device_fault(struct device *dev, struct iommu_fault_event 
> *evt)
> +{
> + /* we only report device fault if there is a handler registered */
> + if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> + !dev->iommu_param->fault_param->handler)

Can this replaced by:

if (!iommu_has_device_fault_handler(dev))

?

Best regards,
Lu Baolu

> + return -ENOSYS;
> +
> + return dev->iommu_param->fault_param->handler(evt,
> + 
> dev->iommu_param->fault_param->data);

Re: [PATCH v3 10/16] iommu: introduce device fault report API

[Lu Baolu]

Hi,

On 11/18/2017 02:55 AM, Jacob Pan wrote:
> Traditionally, device specific faults are detected and handled within
> their own device drivers. When IOMMU is enabled, faults such as DMA
> related transactions are detected by IOMMU. There is no generic
> reporting mechanism to report faults back to the in-kernel device
> driver or the guest OS in case of assigned devices.
>
> Faults detected by IOMMU is based on the transaction's source ID which
> can be reported at per device basis, regardless of the device type is a
> PCI device or not.
>
> The fault types include recoverable (e.g. page request) and
> unrecoverable faults(e.g. access error). In most cases, faults can be
> handled by IOMMU drivers internally. The primary use cases are as
> follows:
> 1. page request fault originated from an SVM capable device that is
> assigned to guest via vIOMMU. In this case, the first level page tables
> are owned by the guest. Page request must be propagated to the guest to
> let guest OS fault in the pages then send page response. In this
> mechanism, the direct receiver of IOMMU fault notification is VFIO,
> which can relay notification events to QEMU or other user space
> software.
>
> 2. faults need more subtle handling by device drivers. Other than
> simply invoke reset function, there are needs to let device driver
> handle the fault with a smaller impact.
>
> This patchset is intended to create a generic fault report API such
> that it can scale as follows:
> - all IOMMU types
> - PCI and non-PCI devices
> - recoverable and unrecoverable faults
> - VFIO and other other in kernel users
> - DMA & IRQ remapping (TBD)
> The original idea was brought up by David Woodhouse and discussions
> summarized at https://lwn.net/Articles/608914/.
>
> Signed-off-by: Jacob Pan 
> Signed-off-by: Ashok Raj 
> ---
>  drivers/iommu/iommu.c | 63 
> ++-
>  include/linux/iommu.h | 36 +
>  2 files changed, 98 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 829e9e9..97b7990 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -581,6 +581,12 @@ int iommu_group_add_device(struct iommu_group *group, 
> struct device *dev)
>   goto err_free_name;
>   }
>  
> + dev->iommu_param = kzalloc(sizeof(struct iommu_fault_param), 
> GFP_KERNEL);
> + if (!dev->iommu_param) {
> + ret = -ENOMEM;
> + goto err_free_name;
> + }
> +
>   kobject_get(group->devices_kobj);
>  
>   dev->iommu_group = group;
> @@ -657,7 +663,7 @@ void iommu_group_remove_device(struct device *dev)
>   sysfs_remove_link(>kobj, "iommu_group");
>  
>   trace_remove_device_from_group(group->id, dev);
> -
> + kfree(dev->iommu_param);
>   kfree(device->name);
>   kfree(device);
>   dev->iommu_group = NULL;
> @@ -791,6 +797,61 @@ int iommu_group_unregister_notifier(struct iommu_group 
> *group,
>  }
>  EXPORT_SYMBOL_GPL(iommu_group_unregister_notifier);
>  
> +int iommu_register_device_fault_handler(struct device *dev,
> + iommu_dev_fault_handler_t handler,
> + void *data)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + /*
> +  * Device iommu_param should have been allocated when device is
> +  * added to its iommu_group.
> +  */
> + if (!idata)
> + return -EINVAL;
> + /* Only allow one fault handler registered for each device */
> + if (idata->fault_param)
> + return -EBUSY;
> + get_device(dev);
> + idata->fault_param =
> + kzalloc(sizeof(struct iommu_fault_param), GFP_KERNEL);
> + if (!idata->fault_param)
> + return -ENOMEM;
> + idata->fault_param->handler = handler;
> + idata->fault_param->data = data;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_register_device_fault_handler);
> +
> +int iommu_unregister_device_fault_handler(struct device *dev)
> +{
> + struct iommu_param *idata = dev->iommu_param;
> +
> + if (!idata)
> + return -EINVAL;
> +
> + kfree(idata->fault_param);
> + idata->fault_param = NULL;
> + put_device(dev);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(iommu_unregister_device_fault_handler);
> +
> +
> +int iommu_report_device_fault(struct device *dev, struct iommu_fault_event 
> *evt)
> +{
> + /* we only report device fault if there is a handler registered */
> + if (!dev->iommu_param || !dev->iommu_param->fault_param ||
> + !dev->iommu_param->fault_param->handler)

Can this replaced by:

if (!iommu_has_device_fault_handler(dev))

?

Best regards,
Lu Baolu

> + return -ENOSYS;
> +
> + return dev->iommu_param->fault_param->handler(evt,
> + 
> dev->iommu_param->fault_param->data);
> +}
>