Hi Yi,
On 7/6/20 3:10 PM, Liu, Yi L wrote:
> Hi Eric,
>
>> From: Auger Eric <eric.au...@redhat.com>
>> Sent: Monday, July 6, 2020 6:37 PM
>>
>> Yi,
>>
>> On 7/4/20 1:26 PM, Liu Yi L wrote:
>>> This patch exports iommu nesting capability info to user space through
>>> VFIO. User space is expected to check this info for supported uAPIs (e.g.
>>> PASID alloc/free, bind page table, and cache invalidation) and the vendor
>>> specific format information for first level/stage page table that will be
>>> bound to.
>>>
>>> The nesting info is available only after the nesting iommu type is set
>>> for a container. Current implementation imposes one limitation - one
>>> nesting container should include at most one group. The philosophy of
>>> vfio container is having all groups/devices within the container share
>>> the same IOMMU context. When vSVA is enabled, one IOMMU context could
>>> include one 2nd-level address space and multiple 1st-level address spaces.
>>> While the 2nd-leve address space is reasonably sharable by multiple groups
>> level
>
> oh, yes.
>
>>> , blindly sharing 1st-level address spaces across all groups within the
>>> container might instead break the guest expectation. In the future sub/
>>> super container concept might be introduced to allow partial address space
>>> sharing within an IOMMU context. But for now let's go with this restriction
>>> by requiring singleton container for using nesting iommu features. Below
>>> link has the related discussion about this decision.
>>>
>>> https://lkml.org/lkml/2020/5/15/1028
>>>
>>> Cc: Kevin Tian <kevin.t...@intel.com>
>>> CC: Jacob Pan <jacob.jun....@linux.intel.com>
>>> Cc: Alex Williamson <alex.william...@redhat.com>
>>> Cc: Eric Auger <eric.au...@redhat.com>
>>> Cc: Jean-Philippe Brucker <jean-phili...@linaro.org>
>>> Cc: Joerg Roedel <j...@8bytes.org>
>>> Cc: Lu Baolu <baolu...@linux.intel.com>
>>> Signed-off-by: Liu Yi L <yi.l....@intel.com>
>>> ---
>>> v3 -> v4:
>>> *) address comments against v3.
>>>
>>> v1 -> v2:
>>> *) added in v2
>>> ---
>>>
>>> drivers/vfio/vfio_iommu_type1.c | 105
>> +++++++++++++++++++++++++++++++++++-----
>>> include/uapi/linux/vfio.h | 16 ++++++
>>> 2 files changed, 109 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/vfio/vfio_iommu_type1.c
>>> b/drivers/vfio/vfio_iommu_type1.c
>>> index 7accb59..80623b8 100644
>>> --- a/drivers/vfio/vfio_iommu_type1.c
>>> +++ b/drivers/vfio/vfio_iommu_type1.c
>>> @@ -62,18 +62,20 @@ MODULE_PARM_DESC(dma_entry_limit,
>>> "Maximum number of user DMA mappings per container (65535).");
>>>
>>> struct vfio_iommu {
>>> - struct list_head domain_list;
>>> - struct list_head iova_list;
>>> - struct vfio_domain *external_domain; /* domain for external user */
>>> - struct mutex lock;
>>> - struct rb_root dma_list;
>>> - struct blocking_notifier_head notifier;
>>> - unsigned int dma_avail;
>>> - uint64_t pgsize_bitmap;
>>> - bool v2;
>>> - bool nesting;
>>> - bool dirty_page_tracking;
>>> - bool pinned_page_dirty_scope;
>>> + struct list_head domain_list;
>>> + struct list_head iova_list;
>>> + struct vfio_domain *external_domain; /* domain for
>>> + external user */
>> nit: put the comment before the field?
>
> do you mean below?
>
> + /* domain for external user */
> + struct vfio_domain *external_domain;
yes that's what I meant
>
>>> + struct mutex lock;
>>> + struct rb_root dma_list;
>>> + struct blocking_notifier_head notifier;
>>> + unsigned int dma_avail;
>>> + uint64_t pgsize_bitmap;
>>> + bool v2;
>>> + bool nesting;
>>> + bool dirty_page_tracking;
>>> + bool pinned_page_dirty_scope;
>>> + struct iommu_nesting_info *nesting_info;
>>> };
>>>
>>> struct vfio_domain {
>>> @@ -130,6 +132,9 @@ struct vfio_regions {
>>> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \
>>> (!list_empty(&iommu->domain_list))
>>>
>>> +#define IS_DOMAIN_IN_CONTAINER(iommu) ((iommu->external_domain) || \
>>> + (!list_empty(&iommu->domain_list)))
>> rename into something like CONTAINER_HAS_DOMAIN()?
>
> got it.
>
>>> +
>>> #define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) /
>> BITS_PER_BYTE)
>>>
>>> /*
>>> @@ -1929,6 +1934,13 @@ static void vfio_iommu_iova_insert_copy(struct
>> vfio_iommu *iommu,
>>>
>>> list_splice_tail(iova_copy, iova);
>>> }
>>> +
>>> +static void vfio_iommu_release_nesting_info(struct vfio_iommu *iommu)
>>> +{
>>> + kfree(iommu->nesting_info);
>>> + iommu->nesting_info = NULL;
>>> +}
>>> +
>>> static int vfio_iommu_type1_attach_group(void *iommu_data,
>>> struct iommu_group *iommu_group)
>>> {
>>> @@ -1959,6 +1971,12 @@ static int vfio_iommu_type1_attach_group(void
>> *iommu_data,
>>> }
>>> }
>>>
>>> + /* Nesting type container can include only one group */
>>> + if (iommu->nesting && IS_DOMAIN_IN_CONTAINER(iommu)) {
>>> + mutex_unlock(&iommu->lock);
>>> + return -EINVAL;
>>> + }
>>> +
>>> group = kzalloc(sizeof(*group), GFP_KERNEL);
>>> domain = kzalloc(sizeof(*domain), GFP_KERNEL);
>>> if (!group || !domain) {
>>> @@ -2029,6 +2047,36 @@ static int vfio_iommu_type1_attach_group(void
>> *iommu_data,
>>> if (ret)
>>> goto out_domain;
>>>
>>> + /* Nesting cap info is available only after attaching */
>>> + if (iommu->nesting) {
>>> + struct iommu_nesting_info tmp;
>>> + struct iommu_nesting_info *info;
>>> +
>>> + /* First get the size of vendor specific nesting info */
>>> + ret = iommu_domain_get_attr(domain->domain,
>>> + DOMAIN_ATTR_NESTING,
>>> + &tmp);
>>> + if (ret)
>>> + goto out_detach;
>>> +
>>> + info = kzalloc(tmp.size, GFP_KERNEL);
>> nit: you may directly use iommu->nesting_info
>
> got you.
>
>>> + if (!info) {
>>> + ret = -ENOMEM;
>>> + goto out_detach;
>>> + }
>>> +
>>> + /* Now get the nesting info */
>>> + info->size = tmp.size;
>>> + ret = iommu_domain_get_attr(domain->domain,
>>> + DOMAIN_ATTR_NESTING,
>>> + info);
>>> + if (ret) {
>>> + kfree(info);
>> ... and set it back to NULL here if it fails
>
> and maybe no need to free it here as vfio_iommu_release_nesting_info()
> will free the nesting_info.
>
>>> + goto out_detach;
>>> + }
>>> + iommu->nesting_info = info;
>>> + }
>>> +
>>> /* Get aperture info */
>>> iommu_domain_get_attr(domain->domain, DOMAIN_ATTR_GEOMETRY,
>> &geo);
>>>
>>> @@ -2138,6 +2186,7 @@ static int vfio_iommu_type1_attach_group(void
>> *iommu_data,
>>> return 0;
>>>
>>> out_detach:
>>> + vfio_iommu_release_nesting_info(iommu);
>>> vfio_iommu_detach_group(domain, group);
>>> out_domain:
>>> iommu_domain_free(domain->domain);
>>> @@ -2338,6 +2387,8 @@ static void vfio_iommu_type1_detach_group(void
>> *iommu_data,
>>> vfio_iommu_unmap_unpin_all(iommu);
>>> else
>>>
>> vfio_iommu_unmap_unpin_reaccount(iommu);
>>> +
>>> + vfio_iommu_release_nesting_info(iommu);
>>> }
>>> iommu_domain_free(domain->domain);
>>> list_del(&domain->next);
>>> @@ -2546,6 +2597,30 @@ static int vfio_iommu_migration_build_caps(struct
>> vfio_iommu *iommu,
>>> return vfio_info_add_capability(caps, &cap_mig.header, sizeof(cap_mig));
>>> }
>>>
>>> +static int vfio_iommu_info_add_nesting_cap(struct vfio_iommu *iommu,
>>> + struct vfio_info_cap *caps)
>>> +{
>>> + struct vfio_info_cap_header *header;
>>> + struct vfio_iommu_type1_info_cap_nesting *nesting_cap;
>>> + size_t size;
>>> +
>>> + size = sizeof(*nesting_cap) + iommu->nesting_info->size;
>>> +
>>> + header = vfio_info_cap_add(caps, size,
>>> + VFIO_IOMMU_TYPE1_INFO_CAP_NESTING, 1);
>>> + if (IS_ERR(header))
>>> + return PTR_ERR(header);
>>> +
>>> + nesting_cap = container_of(header,
>>> + struct vfio_iommu_type1_info_cap_nesting,
>>> + header);
>>> +
>>> + memcpy(&nesting_cap->info, iommu->nesting_info,
>>> + iommu->nesting_info->size);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> static int vfio_iommu_type1_get_info(struct vfio_iommu *iommu,
>>> unsigned long arg)
>>> {
>>> @@ -2586,6 +2661,12 @@ static int vfio_iommu_type1_get_info(struct
>> vfio_iommu *iommu,
>>> if (ret)
>>> return ret;
>>>
>>> + if (iommu->nesting_info) {
>>> + ret = vfio_iommu_info_add_nesting_cap(iommu, &caps);
>>> + if (ret)
>>> + return ret;
>>> + }
>>> +
>>> if (caps.size) {
>>> info.flags |= VFIO_IOMMU_INFO_CAPS;
>>>
>>> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
>>> index 9204705..3e3de9c 100644
>>> --- a/include/uapi/linux/vfio.h
>>> +++ b/include/uapi/linux/vfio.h
>>> @@ -1039,6 +1039,22 @@ struct vfio_iommu_type1_info_cap_migration {
>>> __u64 max_dirty_bitmap_size; /* in bytes */
>>> };
>>>
>>> +#define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING 3
>>
>> You may improve the documentation by taking examples from the above caps.
>
> yes, it is. I somehow broke the style. how about below?
>
>
>
> /*
> * The nesting capability allows to report the related capability
> * and info for nesting iommu type.
> *
> * The structures below define version 1 of this capability.
> *
> * User space should check this cap for setup nesting iommu type.
before setting up stage 1 information? The wording above sounds a bit
confusing to me as it can be interpreted as before choosing
VFIO_TYPE1_NESTING_IOMMU.
You also need to document it returns the capability only after a group
is attached - which looks strange by the way -.
Thanks
Eric
> *
> * @info: the nesting info provided by IOMMU driver. Today
> * it is expected to be a struct iommu_nesting_info
> * data.
> #define VFIO_IOMMU_TYPE1_INFO_CAP_NESTING 3
>
> struct vfio_iommu_type1_info_cap_nesting {
> ...
> };
>
>>> +
>>> +/*
>>> + * Reporting nesting info to user space.
>>> + *
>>> + * @info: the nesting info provided by IOMMU driver. Today
>>> + * it is expected to be a struct iommu_nesting_info
>>> + * data.
>> Is it expected to change?
>
> honestly, I'm not quite sure on it. I did considered to embed
> struct iommu_nesting_info here instead of using info[]. but I
> hesitated as using info[] may leave more flexibility on this
> struct. how about your opinion? perhaps it's fine to embed the
> struct iommu_nesting_info here as long as VFIO is setup nesting
> based on IOMMU UAPI.
>
>>> + */
>>> +struct vfio_iommu_type1_info_cap_nesting {
>>> + struct vfio_info_cap_header header;
>>> + __u32 flags;
>> You may document flags.
>
> sure. it's reserved for future.
>
> Regards,
> Yi Liu
>
>>> + __u32 padding;
>>> + __u8 info[];
>>> +};
>>> +
>>> #define VFIO_IOMMU_GET_INFO _IO(VFIO_TYPE, VFIO_BASE + 12)
>>>
>>> /**
>>>
>> Thanks
>>
>> Eric
>
