Subject: Re: [PATCH v4 02/26] iommu/sva: Manage process address spaces

From: Jonathan Cameron <[email-masked]>
Date: Wed, 26 Feb 2020 12:35:06 +0000

On Mon, 24 Feb 2020 19:23:37 +0100
Jean-Philippe Brucker <[email-masked]> wrote:

> From: Jean-Philippe Brucker <[email-masked]>
> 
> Add a small library to help IOMMU drivers manage process address spaces
> bound to their devices. Register an MMU notifier to track modification
> on each address space bound to one or more devices.
> 
> IOMMU drivers must implement the io_mm_ops and can then use the helpers
> provided by this library to easily implement the SVA API introduced by
> commit 26b25a2b98e4. The io_mm_ops are:
> 
> void *alloc(struct mm_struct *)
>   Allocate a PASID context private to the IOMMU driver. There is a
>   single context per mm. IOMMU drivers may perform arch-specific
>   operations in there, for example pinning down a CPU ASID (on Arm).
> 
> int attach(struct device *, int pasid, void *ctx, bool attach_domain)
>   Attach a context to the device, by setting up the PASID table entry.
> 
> int invalidate(struct device *, int pasid, void *ctx,
>                unsigned long vaddr, size_t size)
>   Invalidate TLB entries for this address range.
> 
> int detach(struct device *, int pasid, void *ctx, bool detach_domain)
>   Detach a context from the device, by clearing the PASID table entry
>   and invalidating cached entries.
> 
> void free(void *ctx)
>   Free a context.
> 
> Signed-off-by: Jean-Philippe Brucker <[email-masked]>

Hi Jean-Phillippe,

A few trivial comments from me in line.  Otherwise this all seems sensible.

Jonathan

> ---
>  drivers/iommu/Kconfig     |   7 +
>  drivers/iommu/Makefile    |   1 +
>  drivers/iommu/iommu-sva.c | 561 ++++++++++++++++++++++++++++++++++++++
>  drivers/iommu/iommu-sva.h |  64 +++++
>  drivers/iommu/iommu.c     |   1 +
>  include/linux/iommu.h     |   3 +
>  6 files changed, 637 insertions(+)
>  create mode 100644 drivers/iommu/iommu-sva.c
>  create mode 100644 drivers/iommu/iommu-sva.h
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index d2fade984999..acca20e2da2f 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -102,6 +102,13 @@ config IOMMU_DMA
>  	select IRQ_MSI_IOMMU
>  	select NEED_SG_DMA_LENGTH
>  
> +# Shared Virtual Addressing library
> +config IOMMU_SVA
> +	bool
> +	select IOASID
> +	select IOMMU_API
> +	select MMU_NOTIFIER
> +
>  config FSL_PAMU
>  	bool "Freescale IOMMU support"
>  	depends on PCI
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index 9f33fdb3bb05..40c800dd4e3e 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -37,3 +37,4 @@ obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
>  obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
>  obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
>  obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
> +obj-$(CONFIG_IOMMU_SVA) += iommu-sva.o
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> new file mode 100644
> index 000000000000..64f1d1c82383
> --- /dev/null
> +++ b/drivers/iommu/iommu-sva.c
> @@ -0,0 +1,561 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Manage PASIDs and bind process address spaces to devices.
> + *
> + * Copyright (C) 2018 ARM Ltd.

Worth updating the date?

> + */
> +
> +#include <linux/idr.h>
> +#include <linux/ioasid.h>
> +#include <linux/iommu.h>
> +#include <linux/sched/mm.h>
> +#include <linux/slab.h>
> +#include <linux/spinlock.h>
> +
> +#include "iommu-sva.h"
> +
> +/**
> + * DOC: io_mm model
> + *
> + * The io_mm keeps track of process address spaces shared between CPU and IOMMU.
> + * The following example illustrates the relation between structures
> + * iommu_domain, io_mm and iommu_sva. The iommu_sva struct is a bond between
> + * io_mm and device. A device can have multiple io_mm and an io_mm may be bound
> + * to multiple devices.
> + *              ___________________________
> + *             |  IOMMU domain A           |
> + *             |  ________________         |
> + *             | |  IOMMU group   |        +------- io_pgtables
> + *             | |                |        |
> + *             | |   dev 00:00.0 ----+------- bond 1 --- io_mm X
> + *             | |________________|   \    |
> + *             |                       '----- bond 2 ---.
> + *             |___________________________|             \
> + *              ___________________________               \
> + *             |  IOMMU domain B           |             io_mm Y
> + *             |  ________________         |             / /
> + *             | |  IOMMU group   |        |            / /
> + *             | |                |        |           / /
> + *             | |   dev 00:01.0 ------------ bond 3 -' /
> + *             | |   dev 00:01.1 ------------ bond 4 --'
> + *             | |________________|        |
> + *             |                           +------- io_pgtables
> + *             |___________________________|
> + *
> + * In this example, device 00:00.0 is in domain A, devices 00:01.* are in domain
> + * B. All devices within the same domain access the same address spaces. Device
> + * 00:00.0 accesses address spaces X and Y, each corresponding to an mm_struct.
> + * Devices 00:01.* only access address space Y. In addition each
> + * IOMMU_DOMAIN_DMA domain has a private address space, io_pgtable, that is
> + * managed with iommu_map()/iommu_unmap(), and isn't shared with the CPU MMU.
> + *
> + * To obtain the above configuration, users would for instance issue the
> + * following calls:
> + *
> + *     iommu_sva_bind_device(dev 00:00.0, mm X, ...) -> bond 1
> + *     iommu_sva_bind_device(dev 00:00.0, mm Y, ...) -> bond 2
> + *     iommu_sva_bind_device(dev 00:01.0, mm Y, ...) -> bond 3
> + *     iommu_sva_bind_device(dev 00:01.1, mm Y, ...) -> bond 4
> + *
> + * A single Process Address Space ID (PASID) is allocated for each mm. In the
> + * example, devices use PASID 1 to read/write into address space X and PASID 2
> + * to read/write into address space Y. Calling iommu_sva_get_pasid() on bond 1
> + * returns 1, and calling it on bonds 2-4 returns 2.
> + *
> + * Hardware tables describing this configuration in the IOMMU would typically
> + * look like this:
> + *
> + *                                PASID tables
> + *                                 of domain A
> + *                              .->+--------+
> + *                             / 0 |        |-------> io_pgtable
> + *                            /    +--------+
> + *            Device tables  /   1 |        |-------> pgd X
> + *              +--------+  /      +--------+
> + *      00:00.0 |      A |-'     2 |        |--.
> + *              +--------+         +--------+   \
> + *              :        :       3 |        |    \
> + *              +--------+         +--------+     --> pgd Y
> + *      00:01.0 |      B |--.                    /
> + *              +--------+   \                  |
> + *      00:01.1 |      B |----+   PASID tables  |
> + *              +--------+     \   of domain B  |
> + *                              '->+--------+   |
> + *                               0 |        |-- | --> io_pgtable
> + *                                 +--------+   |
> + *                               1 |        |   |
> + *                                 +--------+   |
> + *                               2 |        |---'
> + *                                 +--------+
> + *                               3 |        |
> + *                                 +--------+
> + *
> + * With this model, a single call binds all devices in a given domain to an
> + * address space. Other devices in the domain will get the same bond implicitly.
> + * However, users must issue one bind() for each device, because IOMMUs may
> + * implement SVA differently. Furthermore, mandating one bind() per device
> + * allows the driver to perform sanity-checks on device capabilities.

> + *
> + * In some IOMMUs, one entry of the PASID table (typically the first one) can
> + * hold non-PASID translations. In this case PASID 0 is reserved and the first
> + * entry points to the io_pgtable pointer. In other IOMMUs the io_pgtable
> + * pointer is held in the device table and PASID 0 is available to the
> + * allocator.

Is it worth hammering home in here that we can only do this because the PASID space
is global (with exception of PASID 0)?  It's a convenient simplification but not
necessarily a hardware restriction so perhaps we should remind people somewhere in here?

> + */
> +
> +struct io_mm {
> +	struct list_head		devices;
> +	struct mm_struct		*mm;
> +	struct mmu_notifier		notifier;
> +
> +	/* Late initialization */
> +	const struct io_mm_ops		*ops;
> +	void				*ctx;
> +	int				pasid;
> +};
> +
> +#define to_io_mm(mmu_notifier)	container_of(mmu_notifier, struct io_mm, notifier)
> +#define to_iommu_bond(handle)	container_of(handle, struct iommu_bond, sva)

Code ordering wise, do we want this after the definition of iommu_bond?

For both of these it's a bit non obvious what they come 'from'.
I wouldn't naturally assume to_io_mm gets me from notifier to the io_mm
for example.  Not sure it matters though if these are only used in a few
places.

> +
> +struct iommu_bond {
> +	struct iommu_sva		sva;
> +	struct io_mm __rcu		*io_mm;
> +
> +	struct list_head		mm_head;
> +	void				*drvdata;
> +	struct rcu_head			rcu_head;
> +	refcount_t			refs;
> +};
> +
> +static DECLARE_IOASID_SET(shared_pasid);
> +
> +static struct mmu_notifier_ops iommu_mmu_notifier_ops;
> +
> +/*
> + * Serializes modifications of bonds.
> + * Lock order: Device SVA mutex; global SVA mutex; IOASID lock
> + */
> +static DEFINE_MUTEX(iommu_sva_lock);
> +
> +struct io_mm_alloc_params {
> +	const struct io_mm_ops *ops;
> +	int min_pasid, max_pasid;
> +};
> +
> +static struct mmu_notifier *io_mm_alloc(struct mm_struct *mm, void *privdata)
> +{
> +	int ret;
> +	struct io_mm *io_mm;
> +	struct io_mm_alloc_params *params = privdata;
> +
> +	io_mm = kzalloc(sizeof(*io_mm), GFP_KERNEL);
> +	if (!io_mm)
> +		return ERR_PTR(-ENOMEM);
> +
> +	io_mm->mm = mm;
> +	io_mm->ops = params->ops;
> +	INIT_LIST_HEAD(&io_mm->devices);
> +
> +	io_mm->pasid = ioasid_alloc(&shared_pasid, params->min_pasid,
> +				    params->max_pasid, io_mm->mm);
> +	if (io_mm->pasid == INVALID_IOASID) {
> +		ret = -ENOSPC;
> +		goto err_free_io_mm;
> +	}
> +
> +	io_mm->ctx = params->ops->alloc(mm);
> +	if (IS_ERR(io_mm->ctx)) {
> +		ret = PTR_ERR(io_mm->ctx);
> +		goto err_free_pasid;
> +	}
> +	return &io_mm->notifier;
> +
> +err_free_pasid:
> +	ioasid_free(io_mm->pasid);
> +err_free_io_mm:
> +	kfree(io_mm);
> +	return ERR_PTR(ret);
> +}
> +
> +static void io_mm_free(struct mmu_notifier *mn)
> +{
> +	struct io_mm *io_mm = to_io_mm(mn);
> +
> +	WARN_ON(!list_empty(&io_mm->devices));
> +
> +	io_mm->ops->release(io_mm->ctx);
> +	ioasid_free(io_mm->pasid);
> +	kfree(io_mm);
> +}
> +
> +/*
> + * io_mm_get - Allocate an io_mm or get the existing one for the given mm
> + * @mm: the mm
> + * @ops: callbacks for the IOMMU driver
> + * @min_pasid: minimum PASID value (inclusive)
> + * @max_pasid: maximum PASID value (inclusive)
> + *
> + * Returns a valid io_mm or an error pointer.
> + */
> +static struct io_mm *io_mm_get(struct mm_struct *mm,
> +			       const struct io_mm_ops *ops,
> +			       int min_pasid, int max_pasid)
> +{
> +	struct io_mm *io_mm;
> +	struct mmu_notifier *mn;
> +	struct io_mm_alloc_params params = {
> +		.ops		= ops,
> +		.min_pasid	= min_pasid,
> +		.max_pasid	= max_pasid,
> +	};
> +
> +	/*
> +	 * A single notifier can exist for this (ops, mm) pair. Allocate it if
> +	 * necessary.
> +	 */
> +	mn = mmu_notifier_get(&iommu_mmu_notifier_ops, mm, &params);
> +	if (IS_ERR(mn))
> +		return ERR_CAST(mn);
> +	io_mm = to_io_mm(mn);
> +
> +	if (WARN_ON(io_mm->ops != ops)) {
> +		mmu_notifier_put(mn);
> +		return ERR_PTR(-EINVAL);
> +	}
> +
> +	return io_mm;
> +}
> +
> +static void io_mm_put(struct io_mm *io_mm)
> +{
> +	mmu_notifier_put(&io_mm->notifier);
> +}
> +
> +static struct iommu_sva *
> +io_mm_attach(struct device *dev, struct io_mm *io_mm, void *drvdata)
> +{
> +	int ret = 0;

I'm fairly sure this is set in all paths below.  Now, of course the
compiler might not think that in which case fair enough :)

> +	bool attach_domain = true;
> +	struct iommu_bond *bond, *tmp;
> +	struct iommu_domain *domain, *other;
> +	struct iommu_sva_param *param = dev->iommu_param->sva_param;
> +
> +	domain = iommu_get_domain_for_dev(dev);
> +
> +	bond = kzalloc(sizeof(*bond), GFP_KERNEL);
> +	if (!bond)
> +		return ERR_PTR(-ENOMEM);
> +
> +	bond->sva.dev	= dev;
> +	bond->drvdata	= drvdata;
> +	refcount_set(&bond->refs, 1);
> +	RCU_INIT_POINTER(bond->io_mm, io_mm);
> +
> +	mutex_lock(&iommu_sva_lock);
> +	/* Is it already bound to the device or domain? */
> +	list_for_each_entry(tmp, &io_mm->devices, mm_head) {
> +		if (tmp->sva.dev != dev) {
> +			other = iommu_get_domain_for_dev(tmp->sva.dev);
> +			if (domain == other)
> +				attach_domain = false;
> +
> +			continue;
> +		}
> +
> +		if (WARN_ON(tmp->drvdata != drvdata)) {
> +			ret = -EINVAL;
> +			goto err_free;
> +		}
> +
> +		/*
> +		 * Hold a single io_mm reference per bond. Note that we can't
> +		 * return an error after this, otherwise the caller would drop
> +		 * an additional reference to the io_mm.
> +		 */
> +		refcount_inc(&tmp->refs);
> +		io_mm_put(io_mm);
> +		kfree(bond);

Free outside the lock would be ever so slightly more logical given we allocated
before taking the lock.

> +		mutex_unlock(&iommu_sva_lock);
> +		return &tmp->sva;
> +	}
> +
> +	list_add_rcu(&bond->mm_head, &io_mm->devices);
> +	param->nr_bonds++;
> +	mutex_unlock(&iommu_sva_lock);
> +
> +	ret = io_mm->ops->attach(bond->sva.dev, io_mm->pasid, io_mm->ctx,
> +				 attach_domain);
> +	if (ret)
> +		goto err_remove;
> +
> +	return &bond->sva;
> +
> +err_remove:
> +	/*
> +	 * At this point concurrent threads may have started to access the
> +	 * io_mm->devices list in order to invalidate address ranges, which
> +	 * requires to free the bond via kfree_rcu()
> +	 */
> +	mutex_lock(&iommu_sva_lock);
> +	param->nr_bonds--;
> +	list_del_rcu(&bond->mm_head);
> +
> +err_free:
> +	mutex_unlock(&iommu_sva_lock);
> +	kfree_rcu(bond, rcu_head);

I don't suppose it matters really but we don't need the rcu free if
we follow the err_free goto.  Perhaps we are cleaner in this case
to not use a unified exit path but do that case inline?

> +	return ERR_PTR(ret);
> +}
> +
> +static void io_mm_detach_locked(struct iommu_bond *bond)
> +{
> +	struct io_mm *io_mm;
> +	struct iommu_bond *tmp;
> +	bool detach_domain = true;
> +	struct iommu_domain *domain, *other;
> +
> +	io_mm = rcu_dereference_protected(bond->io_mm,
> +					  lockdep_is_held(&iommu_sva_lock));
> +	if (!io_mm)
> +		return;
> +
> +	domain = iommu_get_domain_for_dev(bond->sva.dev);
> +
> +	/* Are other devices in the same domain still attached to this mm? */
> +	list_for_each_entry(tmp, &io_mm->devices, mm_head) {
> +		if (tmp == bond)
> +			continue;
> +		other = iommu_get_domain_for_dev(tmp->sva.dev);
> +		if (domain == other) {
> +			detach_domain = false;
> +			break;
> +		}
> +	}
> +
> +	io_mm->ops->detach(bond->sva.dev, io_mm->pasid, io_mm->ctx,
> +			   detach_domain);
> +
> +	list_del_rcu(&bond->mm_head);
> +	RCU_INIT_POINTER(bond->io_mm, NULL);
> +
> +	/* Free after RCU grace period */
> +	io_mm_put(io_mm);
> +}
> +
> +/*
> + * io_mm_release - release MMU notifier
> + *
> + * Called when the mm exits. Some devices may still be bound to the io_mm. A few
> + * things need to be done before it is safe to release:
> + *
> + * - Tell the device driver to stop using this PASID.
> + * - Clear the PASID table and invalidate TLBs.
> + * - Drop all references to this io_mm.
> + */
> +static void io_mm_release(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> +	struct iommu_bond *bond, *next;
> +	struct io_mm *io_mm = to_io_mm(mn);
> +
> +	mutex_lock(&iommu_sva_lock);
> +	list_for_each_entry_safe(bond, next, &io_mm->devices, mm_head) {
> +		struct device *dev = bond->sva.dev;
> +		struct iommu_sva *sva = &bond->sva;
> +
> +		if (sva->ops && sva->ops->mm_exit &&
> +		    sva->ops->mm_exit(dev, sva, bond->drvdata))
> +			dev_WARN(dev, "possible leak of PASID %u",
> +				 io_mm->pasid);
> +
> +		/* unbind() frees the bond, we just detach it */
> +		io_mm_detach_locked(bond);
> +	}
> +	mutex_unlock(&iommu_sva_lock);
> +}
> +
> +static void io_mm_invalidate_range(struct mmu_notifier *mn,
> +				   struct mm_struct *mm, unsigned long start,
> +				   unsigned long end)
> +{
> +	struct iommu_bond *bond;
> +	struct io_mm *io_mm = to_io_mm(mn);
> +
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(bond, &io_mm->devices, mm_head)
> +		io_mm->ops->invalidate(bond->sva.dev, io_mm->pasid, io_mm->ctx,
> +				       start, end - start);
> +	rcu_read_unlock();
> +}
> +
> +static struct mmu_notifier_ops iommu_mmu_notifier_ops = {
> +	.alloc_notifier		= io_mm_alloc,
> +	.free_notifier		= io_mm_free,
> +	.release		= io_mm_release,
> +	.invalidate_range	= io_mm_invalidate_range,
> +};
> +
> +struct iommu_sva *
> +iommu_sva_bind_generic(struct device *dev, struct mm_struct *mm,
> +		       const struct io_mm_ops *ops, void *drvdata)
> +{
> +	struct io_mm *io_mm;
> +	struct iommu_sva *handle;
> +	struct iommu_param *param = dev->iommu_param;
> +
> +	if (!param)
> +		return ERR_PTR(-ENODEV);
> +
> +	mutex_lock(&param->sva_lock);
> +	if (!param->sva_param) {
> +		handle = ERR_PTR(-ENODEV);
> +		goto out_unlock;
> +	}
> +
> +	io_mm = io_mm_get(mm, ops, param->sva_param->min_pasid,
> +			  param->sva_param->max_pasid);
> +	if (IS_ERR(io_mm)) {
> +		handle = ERR_CAST(io_mm);
> +		goto out_unlock;
> +	}
> +
> +	handle = io_mm_attach(dev, io_mm, drvdata);
> +	if (IS_ERR(handle))
> +		io_mm_put(io_mm);
> +
> +out_unlock:
> +	mutex_unlock(&param->sva_lock);
> +	return handle;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_bind_generic);
> +
> +static void iommu_sva_unbind_locked(struct iommu_bond *bond)
> +{
> +	struct device *dev = bond->sva.dev;
> +	struct iommu_sva_param *param = dev->iommu_param->sva_param;
> +
> +	if (!refcount_dec_and_test(&bond->refs))
> +		return;
> +
> +	io_mm_detach_locked(bond);
> +	param->nr_bonds--;
> +	kfree_rcu(bond, rcu_head);
> +}
> +
> +void iommu_sva_unbind_generic(struct iommu_sva *handle)
> +{
> +	struct iommu_param *param = handle->dev->iommu_param;
> +
> +	if (WARN_ON(!param))
> +		return;
> +
> +	mutex_lock(&param->sva_lock);
> +	mutex_lock(&iommu_sva_lock);
> +	iommu_sva_unbind_locked(to_iommu_bond(handle));
> +	mutex_unlock(&iommu_sva_lock);
> +	mutex_unlock(&param->sva_lock);
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_unbind_generic);
> +
> +/**
> + * iommu_sva_enable() - Enable Shared Virtual Addressing for a device
> + * @dev: the device
> + * @sva_param: the parameters.
> + *
> + * Called by an IOMMU driver to setup the SVA parameters
> + * @sva_param is duplicated and can be freed when this function returns.
> + *
> + * Return 0 if initialization succeeded, or an error.
> + */
> +int iommu_sva_enable(struct device *dev, struct iommu_sva_param *sva_param)
> +{
> +	int ret;
> +	struct iommu_sva_param *new_param;
> +	struct iommu_param *param = dev->iommu_param;
> +
> +	if (!param)
> +		return -ENODEV;
> +
> +	new_param = kmemdup(sva_param, sizeof(*new_param), GFP_KERNEL);
> +	if (!new_param)
> +		return -ENOMEM;
> +
> +	mutex_lock(&param->sva_lock);
> +	if (param->sva_param) {
> +		ret = -EEXIST;
> +		goto err_unlock;
> +	}
> +
> +	dev->iommu_param->sva_param = new_param;
> +	mutex_unlock(&param->sva_lock);
> +	return 0;
> +
> +err_unlock:
> +	mutex_unlock(&param->sva_lock);
> +	kfree(new_param);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_enable);
> +
> +/**
> + * iommu_sva_disable() - Disable Shared Virtual Addressing for a device
> + * @dev: the device
> + *
> + * IOMMU drivers call this to disable SVA.
> + */
> +int iommu_sva_disable(struct device *dev)
> +{
> +	int ret = 0;
> +	struct iommu_param *param = dev->iommu_param;
> +
> +	if (!param)
> +		return -EINVAL;
> +
> +	mutex_lock(&param->sva_lock);
> +	if (!param->sva_param) {
> +		ret = -ENODEV;
> +		goto out_unlock;
> +	}
> +
> +	/* Require that all contexts are unbound */
> +	if (param->sva_param->nr_bonds) {
> +		ret = -EBUSY;
> +		goto out_unlock;
> +	}
> +
> +	kfree(param->sva_param);
> +	param->sva_param = NULL;
> +out_unlock:
> +	mutex_unlock(&param->sva_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_disable);
> +
> +bool iommu_sva_enabled(struct device *dev)
> +{
> +	bool enabled;
> +	struct iommu_param *param = dev->iommu_param;
> +
> +	if (!param)
> +		return false;
> +
> +	mutex_lock(&param->sva_lock);
> +	enabled = !!param->sva_param;
> +	mutex_unlock(&param->sva_lock);
> +	return enabled;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_enabled);
> +
> +int iommu_sva_get_pasid_generic(struct iommu_sva *handle)
> +{
> +	struct io_mm *io_mm;
> +	int pasid = IOMMU_PASID_INVALID;
> +	struct iommu_bond *bond = to_iommu_bond(handle);
> +
> +	rcu_read_lock();
> +	io_mm = rcu_dereference(bond->io_mm);
> +	if (io_mm)
> +		pasid = io_mm->pasid;
> +	rcu_read_unlock();
> +	return pasid;
> +}
> +EXPORT_SYMBOL_GPL(iommu_sva_get_pasid_generic);
> diff --git a/drivers/iommu/iommu-sva.h b/drivers/iommu/iommu-sva.h
> new file mode 100644
> index 000000000000..dd55c2db0936
> --- /dev/null
> +++ b/drivers/iommu/iommu-sva.h
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * SVA library for IOMMU drivers
> + */
> +#ifndef _IOMMU_SVA_H
> +#define _IOMMU_SVA_H
> +
> +#include <linux/iommu.h>
> +#include <linux/kref.h>
> +#include <linux/mmu_notifier.h>
> +
> +struct io_mm_ops {
> +	/* Allocate a PASID context for an mm */
> +	void *(*alloc)(struct mm_struct *mm);
> +
> +	/*
> +	 * Attach a PASID context to a device. Write the entry into the PASID
> +	 * table.
> +	 *
> +	 * @attach_domain is true when no other device in the IOMMU domain is
> +	 *   already attached to this context. IOMMU drivers that share the
> +	 *   PASID tables within a domain don't need to write the PASID entry
> +	 *   when @attach_domain is false.
> +	 */
> +	int (*attach)(struct device *dev, int pasid, void *ctx,
> +		      bool attach_domain);
> +
> +	/*
> +	 * Detach a PASID context from a device. Clear the entry from the PASID
> +	 * table and invalidate if necessary.
> +	 *
> +	 * @detach_domain is true when no other device in the IOMMU domain is
> +	 *   still attached to this context. IOMMU drivers that share the PASID
> +	 *   table within a domain don't need to clear the PASID entry when
> +	 *   @detach_domain is false, only invalidate the caches.
> +	 */
> +	void (*detach)(struct device *dev, int pasid, void *ctx,
> +		       bool detach_domain);
> +
> +	/* Invalidate a range of addresses. Cannot sleep. */
> +	void (*invalidate)(struct device *dev, int pasid, void *ctx,
> +			   unsigned long vaddr, size_t size);
> +
> +	/* Free a context. Cannot sleep. */
> +	void (*release)(void *ctx);
> +};
> +
> +struct iommu_sva_param {
> +	u32			min_pasid;
> +	u32			max_pasid;
> +	int			nr_bonds;
> +};
> +
> +struct iommu_sva *
> +iommu_sva_bind_generic(struct device *dev, struct mm_struct *mm,
> +		       const struct io_mm_ops *ops, void *drvdata);
> +void iommu_sva_unbind_generic(struct iommu_sva *handle);
> +int iommu_sva_get_pasid_generic(struct iommu_sva *handle);
> +
> +int iommu_sva_enable(struct device *dev, struct iommu_sva_param *sva_param);
> +int iommu_sva_disable(struct device *dev);
> +bool iommu_sva_enabled(struct device *dev);
> +
> +#endif /* _IOMMU_SVA_H */
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 3e3528436e0b..c8bd972c1788 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -164,6 +164,7 @@ static struct iommu_param *iommu_get_dev_param(struct device *dev)
>  		return NULL;
>  
>  	mutex_init(&param->lock);
> +	mutex_init(&param->sva_lock);
>  	dev->iommu_param = param;
>  	return param;
>  }
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 1739f8a7a4b4..83397ae88d2d 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -368,6 +368,7 @@ struct iommu_fault_param {
>   * struct iommu_param - collection of per-device IOMMU data
>   *
>   * @fault_param: IOMMU detected device fault reporting data
> + * @sva_param: IOMMU parameter for SVA
>   *
>   * TODO: migrate other per device data pointers under iommu_dev_data, e.g.
>   *	struct iommu_group	*iommu_group;
> @@ -376,6 +377,8 @@ struct iommu_fault_param {
>  struct iommu_param {
>  	struct mutex lock;
>  	struct iommu_fault_param *fault_param;
> +	struct mutex sva_lock;
> +	struct iommu_sva_param *sva_param;
>  };
>  
>  int  iommu_device_register(struct iommu_device *iommu);

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