Hi Jonathan, Thanks for the review, comments inline below. I saw Jean already took in changes based on your review in his sva/api tree. This is just some additions.
On Tue, 18 Jun 2019 17:50:59 +0100 Jonathan Cameron <jonathan.came...@huawei.com> wrote: > On Sun, 9 Jun 2019 06:44:12 -0700 > Jacob Pan <jacob.jun....@linux.intel.com> wrote: > > > From: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> > > > > Some devices might support multiple DMA address spaces, in > > particular those that have the PCI PASID feature. PASID (Process > > Address Space ID) allows to share process address spaces with > > devices (SVA), partition a device into VM-assignable entities (VFIO > > mdev) or simply provide multiple DMA address space to kernel > > drivers. Add a global PASID allocator usable by different drivers > > at the same time. Name it I/O ASID to avoid confusion with ASIDs > > allocated by arch code, which are usually a separate ID space. > > > > The IOASID space is global. Each device can have its own PASID > > space, but by convention the IOMMU ended up having a global PASID > > space, so that with SVA, each mm_struct is associated to a single > > PASID. > > > > The allocator is primarily used by IOMMU subsystem but in rare > > occasions drivers would like to allocate PASIDs for devices that > > aren't managed by an IOMMU, using the same ID space as IOMMU. > > > > There are two types of allocators: > > 1. default allocator - Always available, uses an XArray to track > > 2. custom allocators - Can be registered at runtime, take precedence > > over the default allocator. > > > > Custom allocators have these attributes: > > - provides platform specific alloc()/free() functions with private > > data. > > - allocation results lookup are not provided by the allocator, > > lookup request must be done by the IOASID framework by its own > > XArray. > > - allocators can be unregistered at runtime, either fallback to the > > next custom allocator or to the default allocator. > > What is the usecase for having a 'stack' of custom allocators? > mainly for hotplug. If a vIOMMU provides custom allocation service to a guest and got hot removed we can use other custom allocators from the stack. > > - custom allocators can share the same set of alloc()/free() > > helpers, in this case they also share the same IOASID space, thus > > the same XArray. > > - switching between allocators requires all outstanding IOASIDs to > > be freed unless the two allocators share the same alloc()/free() > > helpers. > In general this approach has a lot of features where the > justification is missing from this particular patch. It may be > useful to add some more background to this intro? > Good point. Here are the use cases as complexity grow. 1. native (host kernel) PASID/IOASID allocation, this will only use default allocator, users are IOMMU driver or any device drivers. 2. guest with a single vIOMMU. vIOMMU driver will register a custom allocator which eventually calls into the host to allocate system-wide PASID. 3. guest with two or more vIOMMUs but share the same backend to allocate system-wide PASID. IOASID code detects the sharing based on alloc/free ops. 4. guest with two or more vIOMMUs each allocate guest-wide PASIDs. 5. In case of hot plug of vIOMMU, the active custom allocator is chosen from a list established during registration. > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> > > Signed-off-by: Jacob Pan <jacob.jun....@linux.intel.com> > > Link: https://lkml.org/lkml/2019/4/26/462 > > Various comments inline. Given the several cups of coffee this took > to review I may well have misunderstood everything ;) > > Jonathan > > --- > > drivers/iommu/Kconfig | 8 + > > drivers/iommu/Makefile | 1 + > > drivers/iommu/ioasid.c | 427 > > +++++++++++++++++++++++++++++++++++++++++++++++++ > > include/linux/ioasid.h | 74 +++++++++ 4 files changed, 510 > > insertions(+) create mode 100644 drivers/iommu/ioasid.c > > create mode 100644 include/linux/ioasid.h > > > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > > index 83664db..c40c4b5 100644 > > --- a/drivers/iommu/Kconfig > > +++ b/drivers/iommu/Kconfig > > @@ -3,6 +3,13 @@ > > config IOMMU_IOVA > > tristate > > > > +# The IOASID allocator may also be used by non-IOMMU_API users > > +config IOASID > > + tristate > > + help > > + Enable the I/O Address Space ID allocator. A single ID > > space shared > > + between different users. > > + > > # IOMMU_API always gets selected by whoever wants it. > > config IOMMU_API > > bool > > @@ -207,6 +214,7 @@ config INTEL_IOMMU_SVM > > depends on INTEL_IOMMU && X86 > > select PCI_PASID > > select MMU_NOTIFIER > > + select IOASID > > help > > Shared Virtual Memory (SVM) provides a facility for > > devices to access DMA resources through process address space by > > diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile > > index 8c71a15..0efac6f 100644 > > --- a/drivers/iommu/Makefile > > +++ b/drivers/iommu/Makefile > > @@ -7,6 +7,7 @@ obj-$(CONFIG_IOMMU_DMA) += dma-iommu.o > > obj-$(CONFIG_IOMMU_IO_PGTABLE) += io-pgtable.o > > obj-$(CONFIG_IOMMU_IO_PGTABLE_ARMV7S) += io-pgtable-arm-v7s.o > > obj-$(CONFIG_IOMMU_IO_PGTABLE_LPAE) += io-pgtable-arm.o > > +obj-$(CONFIG_IOASID) += ioasid.o > > obj-$(CONFIG_IOMMU_IOVA) += iova.o > > obj-$(CONFIG_OF_IOMMU) += of_iommu.o > > obj-$(CONFIG_MSM_IOMMU) += msm_iommu.o > > diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c > > new file mode 100644 > > index 0000000..0919b70 > > --- /dev/null > > +++ b/drivers/iommu/ioasid.c > > @@ -0,0 +1,427 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * I/O Address Space ID allocator. There is one global IOASID > > space, split into > > + * subsets. Users create a subset with DECLARE_IOASID_SET, then > > allocate and > > + * free IOASIDs with ioasid_alloc and ioasid_free. > > + */ > > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt > > + > > +#include <linux/xarray.h> > > +#include <linux/ioasid.h> > > +#include <linux/slab.h> > > +#include <linux/module.h> > > +#include <linux/spinlock.h> > > + > > +struct ioasid_data { > > + ioasid_t id; > > + struct ioasid_set *set; > > + void *private; > > + struct rcu_head rcu; > > +}; > > + > > +/* > > + * struct ioasid_allocator_data - Internal data structure to hold > > information > > + * about an allocator. There are two types of allocators: > > + * > > + * - Default allocator always has its own XArray to track the > > IOASIDs allocated. > > + * - Custom allocators may share allocation helpers with different > > private data. > > + * Custom allocators share the same helper functions also share > > the same > > + * XArray. > > + * Rules: > > + * 1. Default allocator is always available, not dynamically > > registered. This is > > + * to prevent race conditions with early boot code that want to > > register > > + * custom allocators or allocate IOASIDs. > > + * 2. Custom allocators take precedence over the default allocator. > > + * 3. When all custom allocators sharing the same helper functions > > are > > + * unregistered (e.g. due to hotplug), all outstanding IOASIDs > > must be > > + * freed. > > + * 4. When switching between custom allocators sharing the same > > helper > > + * functions, outstanding IOASIDs are preserved. > > + * 5. When switching between custom allocator and default > > allocator, all IOASIDs > > + * must be freed to ensure unadulterated space for the new > > allocator. > > + * > > + * @ops: allocator helper functions and its data > > + * @list: registered custom allocators > > + * @slist: allocators share the same ops but different data > > + * @flags: attributes of the allocator > > + * @users number of allocators sharing the same ops and > > XArray > > + * @xa xarray holds the IOASID space > Doc ordering should match the struct. > Fixed in Jean's tree. > > + */ > > +struct ioasid_allocator_data { > > + struct ioasid_allocator_ops *ops; > > + struct list_head list; > > + struct list_head slist; > > +#define IOASID_ALLOCATOR_CUSTOM BIT(0) /* Needs framework to track > > results */ > > + unsigned long flags; > > + struct xarray xa; > > + refcount_t users; > > +}; > > + > > +static DEFINE_MUTEX(ioasid_allocator_lock); > > +static LIST_HEAD(allocators_list); > > +static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void > > *opaque); +static void default_free(ioasid_t ioasid, void *opaque); > > + > > +static struct ioasid_allocator_ops default_ops = { > > + .alloc = default_alloc, > > + .free = default_free > > Pure churn prevention but doesn't seem implausible that we'll end up > with more ops at somepoint, so add the commas on last elements? > Sounds good, avoid a new line. Fixed in Jean's tree. > > +}; > > + > > +static struct ioasid_allocator_data default_allocator = { > > + .ops = &default_ops, > > + .flags = 0, > > + .xa = XARRAY_INIT(ioasid_xa, XA_FLAGS_ALLOC) > > +}; > > + > > +static struct ioasid_allocator_data *active_allocator = > > &default_allocator; + > > +static ioasid_t default_alloc(ioasid_t min, ioasid_t max, void > > *opaque) +{ > Why not reorder to avoid having the forward defs above? It's only > moving things a few lines in this case so I'm not seeing a strong > readability argument. > There is a circular dependency. default_alloc() depends on default_allocator which in turn depends on default_ops. > > + ioasid_t id; > > + > > + if (xa_alloc(&default_allocator.xa, &id, opaque, > > XA_LIMIT(min, max), GFP_KERNEL)) { > > + pr_err("Failed to alloc ioasid from %d to %d\n", > > min, max); > > It seems xa_alloc can return a few different error values. Perhaps > worth printing out what we got as might help in debugging? > yes, will do. > > + return INVALID_IOASID; > > + } > > + > > + return id; > > +} > > + > > +void default_free(ioasid_t ioasid, void *opaque) > > +{ > > + struct ioasid_data *ioasid_data; > > + > > + ioasid_data = xa_erase(&default_allocator.xa, ioasid); > > + kfree_rcu(ioasid_data, rcu); > > +} > > + > > +/* Allocate and initialize a new custom allocator with its helper > > functions */ +static inline struct ioasid_allocator_data > > *ioasid_alloc_allocator(struct ioasid_allocator_ops *ops) > > Why inline? > Good catch, fixed by Jean in his tree. > > +{ > > + struct ioasid_allocator_data *ia_data; > > + > > + ia_data = kzalloc(sizeof(*ia_data), GFP_KERNEL); > > + if (!ia_data) > > + return NULL; > > + > > + xa_init_flags(&ia_data->xa, XA_FLAGS_ALLOC); > > + INIT_LIST_HEAD(&ia_data->slist); > > + ia_data->flags |= IOASID_ALLOCATOR_CUSTOM; > > + ia_data->ops = ops; > > + > > + /* For tracking custom allocators that share the same ops > > */ > > + list_add_tail(&ops->list, &ia_data->slist); > > + refcount_set(&ia_data->users, 1); > > + > > + return ia_data; > > +} > > + > > +static inline bool use_same_ops(struct ioasid_allocator_ops *a, > > struct ioasid_allocator_ops *b) +{ > > + return (a->free == b->free) && (a->alloc == b->alloc); > > +} > > + > > +/** > > + * ioasid_register_allocator - register a custom allocator > > + * @ops: the custom allocator ops to be registered > > + * > > + * Custom allocators take precedence over the default xarray based > > allocator. > > + * Private data associated with the IOASID allocated by the custom > > allocators > > + * are managed by IOASID framework similar to data stored in xa by > > default > > + * allocator. > > + * > > + * There can be multiple allocators registered but only one is > > active. In case > > + * of runtime removal of a custom allocator, the next one is > > activated based > > + * on the registration ordering. > > + * > > + * Multiple allocators can share the same alloc() function, in > > this case the > > + * IOASID space is shared. > > + * > Nitpick: This extra blank line seems inconsistent. > fixed by Jean in his tree. > > + */ > > +int ioasid_register_allocator(struct ioasid_allocator_ops *ops) > > +{ > > + struct ioasid_allocator_data *ia_data; > > + struct ioasid_allocator_data *pallocator; > > + int ret = 0; > > + > > + mutex_lock(&ioasid_allocator_lock); > > + > > + ia_data = ioasid_alloc_allocator(ops); > > + if (!ia_data) { > > + ret = -ENOMEM; > > + goto out_unlock; > > + } > > + > > + /* > > + * No particular preference, we activate the first one and > > keep > > + * the later registered allocators in a list in case the > > first one gets > > + * removed due to hotplug. > > + */ > > + if (list_empty(&allocators_list)) { > > + WARN_ON(active_allocator != &default_allocator); > > + /* Use this new allocator if default is not active > > */ > > + if (xa_empty(&active_allocator->xa)) { > > + active_allocator = ia_data; > > + list_add_tail(&ia_data->list, > > &allocators_list); > > + goto out_unlock; > > + } > > + pr_warn("Default allocator active with outstanding > > IOASID\n"); > > + ret = -EAGAIN; > > + goto out_free; > > + } > > + > > + /* Check if the allocator is already registered */ > > + list_for_each_entry(pallocator, &allocators_list, list) { > > + if (pallocator->ops == ops) { > > + pr_err("IOASID allocator already > > registered\n"); > > + ret = -EEXIST; > > + goto out_free; > > + } else if (use_same_ops(pallocator->ops, ops)) { > > + /* > > + * If the new allocator shares the same > > ops, > > + * then they will share the same IOASID > > space. > > + * We should put them under the same > > xarray. > > + */ > > + list_add_tail(&ops->list, > > &pallocator->slist); > > + refcount_inc(&pallocator->users); > > + pr_info("New IOASID allocator ops shared > > %u times\n", > > + refcount_read(&pallocator->users)); > > + goto out_free; > > + } > > + } > > + list_add_tail(&ia_data->list, &allocators_list); > > + > > + goto out_unlock; > I commented on this in Jean-Phillipe's set as well I think. > Cleaner to just have a separate unlock copy here and return. > fixed by Jean in his tree. > > + > > +out_free: > > + kfree(ia_data); > > +out_unlock: > > + mutex_unlock(&ioasid_allocator_lock); > > + return ret; > > +} > > +EXPORT_SYMBOL_GPL(ioasid_register_allocator); > > + > > +static inline bool has_shared_ops(struct ioasid_allocator_data > > *allocator) +{ > > + return refcount_read(&allocator->users) > 1; > > +} > > + > > +/** > > + * ioasid_unregister_allocator - Remove a custom IOASID allocator > > ops > > + * @ops: the custom allocator to be removed > > + * > > + * Remove an allocator from the list, activate the next allocator > > in > > + * the order it was registered. Or revert to default allocator if > > all > > + * custom allocators are unregistered without outstanding IOASIDs. > > + */ > > +void ioasid_unregister_allocator(struct ioasid_allocator_ops *ops) > > +{ > > + struct ioasid_allocator_data *pallocator; > > + struct ioasid_allocator_ops *sops; > > + > > + mutex_lock(&ioasid_allocator_lock); > > + if (list_empty(&allocators_list)) { > > + pr_warn("No custom IOASID allocators active!\n"); > > + goto exit_unlock; > > + } > > + > > + list_for_each_entry(pallocator, &allocators_list, list) { > > + if (use_same_ops(pallocator->ops, ops)) { > Could reduce the depth with. > > if (!use_same_ops(pallocator->ops, ops)) > continue; > > Trade off between having the unusual flow that will resort and the > code going off the side of your screen (if you use a very small > screen ;) > fixed by Jean in his tree. > > + if (refcount_read(&pallocator->users) == > > 1) { > > + /* No shared helper functions */ > > + list_del(&pallocator->list); > > + /* > > + * All IOASIDs should have been > > freed before > > + * the last allocator that shares > > the same ops > > + * is unregistered. > > + */ > > + > > WARN_ON(!xa_empty(&pallocator->xa)); > > + kfree(pallocator); > > + if (list_empty(&allocators_list)) { > > + pr_info("No custom IOASID > > allocators, switch to default.\n"); > > + active_allocator = > > &default_allocator; > > + } else if (pallocator == > > active_allocator) { > > + active_allocator = > > list_entry(&allocators_list, struct ioasid_allocator_data, list); > > What is the intent here? You seem to be calling the list entry > dereference on the list head itself. That will get you something > fairly random on the stack I think. > > list_first_entry maybe? > The intent here is to pick a new active_allocator if the one being unregistered happens to be the active allocator. It should be list_first_entry. Thanks. > > > + pr_info("IOASID allocator > > changed"); > > + } > > + break; > > + } > > + /* > > + * Find the matching shared ops to delete, > > + * but keep outstanding IOASIDs > > + */ > > + list_for_each_entry(sops, > > &pallocator->slist, list) { > > + if (sops == ops) { > > + list_del(&ops->list); > > + if > > (refcount_dec_and_test(&pallocator->users)) > > + pr_err("no shared > > ops\n"); > > + break; > > + } > > + } > > + break; > > + } > > + } > > + > > +exit_unlock: > > + mutex_unlock(&ioasid_allocator_lock); > > +} > > +EXPORT_SYMBOL_GPL(ioasid_unregister_allocator); > > + > > +/** > > + * ioasid_set_data - Set private data for an allocated ioasid > > + * @ioasid: the ID to set data > > + * @data: the private data > > + * > > + * For IOASID that is already allocated, private data can be set > > + * via this API. Future lookup can be done via ioasid_find. > > + */ > > +int ioasid_set_data(ioasid_t ioasid, void *data) > > +{ > > + struct ioasid_data *ioasid_data; > > + int ret = 0; > > + > > + mutex_lock(&ioasid_allocator_lock); > > + ioasid_data = xa_load(&active_allocator->xa, ioasid); > > + if (ioasid_data) > > + ioasid_data->private = data; > > + else > > + ret = -ENOENT; > > + mutex_unlock(&ioasid_allocator_lock); > > + > > + /* getter may use the private data */ > > + synchronize_rcu(); > > + > > + return ret; > > +} > > +EXPORT_SYMBOL_GPL(ioasid_set_data); > > + > > +/** > > + * ioasid_alloc - Allocate an IOASID > > + * @set: the IOASID set > > + * @min: the minimum ID (inclusive) > > + * @max: the maximum ID (inclusive) > > + * @private: data private to the caller > > + * > > + * Allocate an ID between @min and @max. Return the allocated ID > > on success, > > + * or INVALID_IOASID on failure. The @private pointer is stored > > internally > > + * and can be retrieved with ioasid_find(). > > + */ > > +ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, > > ioasid_t max, > > + void *private) > > +{ > > + ioasid_t id = INVALID_IOASID; > > + struct ioasid_data *data; > > + > > + data = kzalloc(sizeof(*data), GFP_KERNEL); > > + if (!data) > > + return INVALID_IOASID; > > + > > + data->set = set; > > + data->private = private; > > + > > + mutex_lock(&ioasid_allocator_lock); > > + > > + id = active_allocator->ops->alloc(min, max, data); > > + if (id == INVALID_IOASID) { > > + pr_err("Failed ASID allocation %lu\n", > > active_allocator->flags); > > + mutex_unlock(&ioasid_allocator_lock); > > + goto exit_free; > > + } > > + if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) { > > + /* Custom allocator needs framework to store and > > track allocation results */ > > + min = id; > > + max = id + 1; > > Looking at xa_limit definition these are inclusive limits so why do > we let it take either value? > you are right, it was idr based which was exclusive. Jean already fixed it. > > + > > + if (xa_alloc(&active_allocator->xa, &id, data, > > XA_LIMIT(min, max), GFP_KERNEL)) { > > + pr_err("Failed to alloc ioasid from %d to > > %d\n", min, max); > > + active_allocator->ops->free(id, NULL); > > + goto exit_free; > > + } > > + } > > + data->id = id; > > + > > + mutex_unlock(&ioasid_allocator_lock); > > + > > +exit_free: > As with the version of the patch without custom allocator, feels like > we can simplify this section as we can't get here with id == > INVALID_IOASID unless we went to the exit_free. > > If we did take the exit_free it is always INVALID_IOASID ( I think, > but haven't checked...) > > So just have a return from the good path and always run > this block i the bad one. > sounds good, fixed in Jean's tree. > > + if (id == INVALID_IOASID) { > > + kfree(data); > > + return INVALID_IOASID; > > + } > > + return id; > > +} > > +EXPORT_SYMBOL_GPL(ioasid_alloc); > > + > > +/** > > + * ioasid_free - Free an IOASID > > + * @ioasid: the ID to remove > > + */ > > +void ioasid_free(ioasid_t ioasid) > > +{ > > + struct ioasid_data *ioasid_data; > > + > > + mutex_lock(&ioasid_allocator_lock); > > + > > + ioasid_data = xa_load(&active_allocator->xa, ioasid); > > + if (!ioasid_data) { > > + pr_err("Trying to free unknown IOASID %u\n", > > ioasid); > > + goto exit_unlock; > > + } > > + > > + active_allocator->ops->free(ioasid, > > active_allocator->ops->pdata); > > + /* Custom allocator needs additional steps to free the xa > > */ > xa element perhaps? > > > + if (active_allocator->flags & IOASID_ALLOCATOR_CUSTOM) { > > + ioasid_data = xa_erase(&active_allocator->xa, > > ioasid); > > + kfree_rcu(ioasid_data, rcu); > > + } > > + > > +exit_unlock: > > + mutex_unlock(&ioasid_allocator_lock); > > +} > > +EXPORT_SYMBOL_GPL(ioasid_free); > > + > > +/** > > + * ioasid_find - Find IOASID data > > + * @set: the IOASID set > > + * @ioasid: the IOASID to find > > + * @getter: function to call on the found object > > + * > > + * The optional getter function allows to take a reference to the > > found object > > + * under the rcu lock. The function can also check if the object > > is still valid: > > + * if @getter returns false, then the object is invalid and NULL > > is returned. > > + * > > + * If the IOASID has been allocated for this set, return the > > private pointer > > + * passed to ioasid_alloc. Private data can be NULL if not set. > > Return an error > > + * if the IOASID is not found or does not belong to the set. > > + */ > > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > > + bool (*getter)(void *)) > > +{ > > + void *priv = NULL; > > Always set so no need to initialize. > right > > + struct ioasid_data *ioasid_data; > > + > > + rcu_read_lock(); > > + ioasid_data = xa_load(&active_allocator->xa, ioasid); > > + if (!ioasid_data) { > > + priv = ERR_PTR(-ENOENT); > > + goto unlock; > > + } > > + if (set && ioasid_data->set != set) { > > + /* data found but does not belong to the set */ > > + priv = ERR_PTR(-EACCES); > > + goto unlock; > > + } > > + /* Now IOASID and its set is verified, we can return the > > private data */ > > + priv = ioasid_data->private; > > + if (getter && !getter(priv)) > > + priv = NULL; > > +unlock: > > + rcu_read_unlock(); > > + > > + return priv; > > +} > > +EXPORT_SYMBOL_GPL(ioasid_find); > > + > > +MODULE_AUTHOR("Jean-Philippe Brucker > > <jean-philippe.bruc...@arm.com>"); +MODULE_AUTHOR("Jacob Pan > > <jacob.jun....@linux.intel.com>"); +MODULE_DESCRIPTION("IO Address > > Space ID (IOASID) allocator"); +MODULE_LICENSE("GPL"); > > diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h > > new file mode 100644 > > index 0000000..8c8d1c5 > > --- /dev/null > > +++ b/include/linux/ioasid.h > > @@ -0,0 +1,74 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#ifndef __LINUX_IOASID_H > > +#define __LINUX_IOASID_H > > + > > +#define INVALID_IOASID ((ioasid_t)-1) > > +typedef unsigned int ioasid_t; > > +typedef ioasid_t (*ioasid_alloc_fn_t)(ioasid_t min, ioasid_t max, > > void *data); +typedef void (*ioasid_free_fn_t)(ioasid_t ioasid, > > void *data); + > > +struct ioasid_set { > > + int dummy; > > +}; > > + > > +/** > > + * struct ioasid_allocator_ops - IOASID allocator helper functions > > and data > > + * > > + * @alloc: helper function to allocate IOASID > > + * @free: helper function to free IOASID > > + * @list: for tracking ops that share helper functions but > > not data > > + * @pdata: data belong to the allocator, provided when > > calling alloc() > and free() > > Seems odd to call out one and not the other. > I'm not actually sure it's true though as I can't see pdata being > provided to the alloc call. > You are right, allocator data should be provided to both free and alloc. There is a bug in my code, should have called with allocator private data instead of IOASID private data. I will fix on top of Jean's version. Thank you so much, > > + */ > > +struct ioasid_allocator_ops { > > + ioasid_alloc_fn_t alloc; > > + ioasid_free_fn_t free; > > + struct list_head list; > > + void *pdata; > > +}; > > + > > +#define DECLARE_IOASID_SET(name) struct ioasid_set name = { 0 } > > I was a little curious on how this would actually be used. > Even more curious is that it isn't used that I can find. > It can be used for data types or ownership permission. For VT-d. We use this as the mm_struct of the PASID allocator to ensure that only IOASID allocated by the same process can operate on it, e.g. free or bind. > > + > > +#if IS_ENABLED(CONFIG_IOASID) > > +ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, > > ioasid_t max, > > + void *private); > > +void ioasid_free(ioasid_t ioasid); > > + > > +void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid, > > + bool (*getter)(void *)); > > +int ioasid_register_allocator(struct ioasid_allocator_ops > > *allocator); +void ioasid_unregister_allocator(struct > > ioasid_allocator_ops *allocator); +int ioasid_set_data(ioasid_t > > ioasid, void *data); + > > +#else /* !CONFIG_IOASID */ > > +static inline ioasid_t ioasid_alloc(struct ioasid_set *set, > > ioasid_t min, > > + ioasid_t max, void *private) > > +{ > > + return INVALID_IOASID; > > +} > > + > > +static inline void ioasid_free(ioasid_t ioasid) > > +{ > > +} > > + > > +static inline void *ioasid_find(struct ioasid_set *set, ioasid_t > > ioasid, > > + bool (*getter)(void *)) > > +{ > > + return NULL; > > +} > > + > > +static inline int ioasid_register_allocator(struct > > ioasid_allocator_ops *allocator) +{ > > + return -ENODEV; > > +} > > + > > +static inline void ioasid_unregister_allocator(struct > > ioasid_allocator_ops *allocator) +{ > > +} > > + > > +static inline int ioasid_set_data(ioasid_t ioasid, void *data) > > +{ > > + return -ENODEV; > > +} > > + > > +#endif /* CONFIG_IOASID */ > > +#endif /* __LINUX_IOASID_H */ > > [Jacob Pan]