Re: [PATCH] i915: purify user ptr ioctl through the fire of truth.

On Mon, Jun 30, 2014 at 02:23:32PM -0400, j.glisse@gmail.com wrote:

From: Jerome Glisse jglisse@redhat.com

Heresy should not be tolerated, any ioctl that rely on pure luck should die. Violating memory pining kernel policy and all the reasonable expection kernel have about user of mmu_notifier api is not tolerable.

Because we can neither broke old userspace the ioctl is left but i will never succeed which is the only reliable option for it.

Signed-off-by: Jérôme Glisse jglisse@redhat.com

As per the irc discussions I've had with Glisse I'll stick with i915 userptr. A few key points:

- userptr is really only valid for X shem and malloced memory. It's very far away from real shared address space (iirc called hmm by amd/nvidia) and doesn't make any guarantees when userspace remaps memory (mmap/unmap) or forks (i.e. cow maps). In that sense userptr is an evolutionary dead-end, but still rather useful.

- The only reason we have the mmu notifier is to be able to opportunistically pin memory with without hitting mlock limits. For that we need to play nice with page migration and swap-out, which our mmu notifier callback allows. If there's a race there's no harm done since both swap-out and page migration either retry or move to victimize another suitable page. Of coures real shared virtual memory would need a rather different mmu notifier implementation (and hw support) to close all the races, but userptr is explicitly not that powerful. If you cow or remap you get to keep all the pieces.

Hence the mmu notifier is really just to be able to keep the page pinned after the batch completes instead of dropping the pinning again like AIO does after a transaction completes.

- Hence we only need correctness wrt swap-out/page-migration. The page references obtained by gup guarantees that without the mmu notifier stuff. That's the same guarantees as aio and friends rely on, so we should be safe (at least for now).

Cheers, Daniel

---

drivers/gpu/drm/i915/i915_drv.h | 15 - drivers/gpu/drm/i915/i915_gem.c | 1 - drivers/gpu/drm/i915/i915_gem_userptr.c | 687 +------------------------------- drivers/gpu/drm/i915/i915_gpu_error.c | 2 - 4 files changed, 5 insertions(+), 700 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h index 8cea596..3970bd0 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h @@ -393,7 +393,6 @@ struct drm_i915_error_state { u32 tiling:2; u32 dirty:1; u32 purgeable:1;

• u32 userptr:1;
  

  s32 ring:4; u32 cache_level:3; } **active_bo, **pinned_bo;

@@ -1750,19 +1749,6 @@ struct drm_i915_gem_object {

/** for phy allocated objects */ drm_dma_handle_t *phys_handle;

• union {

• struct i915_gem_userptr {
  

• 	uintptr_t ptr;
  

• 	unsigned read_only :1;
  

• 	unsigned workers :4;
  

-#define I915_GEM_USERPTR_MAX_WORKERS 15

• 	struct mm_struct *mm;
  

• 	struct i915_mmu_object *mn;
  

• 	struct work_struct *work;
  

• } userptr;
  

• };

}; #define to_intel_bo(x) container_of(x, struct drm_i915_gem_object, base)

@@ -2195,7 +2181,6 @@ int i915_gem_set_tiling(struct drm_device *dev, void *data, struct drm_file *file_priv); int i915_gem_get_tiling(struct drm_device *dev, void *data, struct drm_file *file_priv); -int i915_gem_init_userptr(struct drm_device *dev); int i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file); int i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data, diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c index f6d1238..30fc784 100644 --- a/drivers/gpu/drm/i915/i915_gem.c +++ b/drivers/gpu/drm/i915/i915_gem.c @@ -4754,7 +4754,6 @@ int i915_gem_init(struct drm_device *dev) DRM_DEBUG_DRIVER("allow wake ack timed out\n"); }

• i915_gem_init_userptr(dev); i915_gem_init_global_gtt(dev);

  ret = i915_gem_context_init(dev);

diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c index 191ac71..f261cb9 100644 --- a/drivers/gpu/drm/i915/i915_gem_userptr.c +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c @@ -22,692 +22,15 @@

*/

-#include "drmP.h" #include "i915_drm.h" #include "i915_drv.h" -#include "i915_trace.h" #include "intel_drv.h" -#include <linux/mmu_context.h> -#include <linux/mmu_notifier.h> -#include <linux/mempolicy.h> -#include <linux/swap.h>

-#if defined(CONFIG_MMU_NOTIFIER) -#include <linux/interval_tree.h>

-struct i915_mmu_notifier {

• spinlock_t lock;
• struct hlist_node node;
• struct mmu_notifier mn;
• struct rb_root objects;
• struct drm_device *dev;
• struct mm_struct *mm;
• struct work_struct work;
• unsigned long count;
• unsigned long serial;

-};

-struct i915_mmu_object {

• struct i915_mmu_notifier *mmu;
• struct interval_tree_node it;
• struct drm_i915_gem_object *obj;

-};

-static void i915_gem_userptr_mn_invalidate_range_start(struct mmu_notifier *_mn,

• 				       struct mm_struct *mm,
  

• 				       struct vm_area_struct *vma,
  

• 				       unsigned long start,
  

• 				       unsigned long end,
  

• 				       enum mmu_event event)
  

-{

• struct i915_mmu_notifier *mn = container_of(_mn, struct i915_mmu_notifier, mn);
• struct interval_tree_node *it = NULL;
• unsigned long serial = 0;
• end--; /* interval ranges are inclusive, but invalidate range is exclusive */
• while (start < end) {

• struct drm_i915_gem_object *obj;
  

• obj = NULL;
  

• spin_lock(&mn->lock);
  

• if (serial == mn->serial)
  

• 	it = interval_tree_iter_next(it, start, end);
  

• else
  

• 	it = interval_tree_iter_first(&mn->objects, start, end);
  

• if (it != NULL) {
  

• 	obj = container_of(it, struct i915_mmu_object, it)->obj;
  

• 	drm_gem_object_reference(&obj->base);
  

• 	serial = mn->serial;
  

• }
  

• spin_unlock(&mn->lock);
  

• if (obj == NULL)
  

• 	return;
  

• mutex_lock(&mn->dev->struct_mutex);
  

• /* Cancel any active worker and force us to re-evaluate gup */
  

• obj->userptr.work = NULL;
  

• if (obj->pages != NULL) {
  

• 	struct drm_i915_private *dev_priv = to_i915(mn->dev);
  

• 	struct i915_vma *vma, *tmp;
  

• 	bool was_interruptible;
  

• 	was_interruptible = dev_priv->mm.interruptible;
  

• 	dev_priv->mm.interruptible = false;
  

• 	list_for_each_entry_safe(vma, tmp, &obj->vma_list, vma_link) {
  

• 		int ret = i915_vma_unbind(vma);
  

• 		WARN_ON(ret && ret != -EIO);
  

• 	}
  

• 	WARN_ON(i915_gem_object_put_pages(obj));
  

• 	dev_priv->mm.interruptible = was_interruptible;
  

• }
  

• start = obj->userptr.ptr + obj->base.size;
  

• drm_gem_object_unreference(&obj->base);
  

• mutex_unlock(&mn->dev->struct_mutex);
  

• }

-}

-static const struct mmu_notifier_ops i915_gem_userptr_notifier = {

• .invalidate_range_start = i915_gem_userptr_mn_invalidate_range_start,

-};

-static struct i915_mmu_notifier * -__i915_mmu_notifier_lookup(struct drm_device *dev, struct mm_struct *mm) -{

• struct drm_i915_private *dev_priv = to_i915(dev);
• struct i915_mmu_notifier *mmu;
• /* Protected by dev->struct_mutex */
• hash_for_each_possible(dev_priv->mmu_notifiers, mmu, node, (unsigned long)mm)

• if (mmu->mm == mm)
  

• 	return mmu;
  

• return NULL;

-}

-static struct i915_mmu_notifier * -i915_mmu_notifier_get(struct drm_device *dev, struct mm_struct *mm) -{

• struct drm_i915_private *dev_priv = to_i915(dev);
• struct i915_mmu_notifier *mmu;
• int ret;
• lockdep_assert_held(&dev->struct_mutex);
• mmu = __i915_mmu_notifier_lookup(dev, mm);
• if (mmu)

• return mmu;
  

• mmu = kmalloc(sizeof(*mmu), GFP_KERNEL);
• if (mmu == NULL)

• return ERR_PTR(-ENOMEM);
  

• spin_lock_init(&mmu->lock);
• mmu->dev = dev;
• mmu->mn.ops = &i915_gem_userptr_notifier;
• mmu->mm = mm;
• mmu->objects = RB_ROOT;
• mmu->count = 0;
• mmu->serial = 0;
• /* Protected by mmap_sem (write-lock) */
• ret = __mmu_notifier_register(&mmu->mn, mm);
• if (ret) {

• kfree(mmu);
  

• return ERR_PTR(ret);
  

• }
• /* Protected by dev->struct_mutex */
• hash_add(dev_priv->mmu_notifiers, &mmu->node, (unsigned long)mm);
• return mmu;

-}

-static void -__i915_mmu_notifier_destroy_worker(struct work_struct *work) -{

• struct i915_mmu_notifier *mmu = container_of(work, typeof(*mmu), work);
• mmu_notifier_unregister(&mmu->mn, mmu->mm);
• kfree(mmu);

-}

-static void -__i915_mmu_notifier_destroy(struct i915_mmu_notifier *mmu) -{

• lockdep_assert_held(&mmu->dev->struct_mutex);
• /* Protected by dev->struct_mutex */
• hash_del(&mmu->node);
• /* Our lock ordering is: mmap_sem, mmu_notifier_scru, struct_mutex.

• * We enter the function holding struct_mutex, therefore we need
  

• * to drop our mutex prior to calling mmu_notifier_unregister in
  

• * order to prevent lock inversion (and system-wide deadlock)
  

• * between the mmap_sem and struct-mutex. Hence we defer the
  

• * unregistration to a workqueue where we hold no locks.
  

• */
  

• INIT_WORK(&mmu->work, __i915_mmu_notifier_destroy_worker);
• schedule_work(&mmu->work);

-}

-static void __i915_mmu_notifier_update_serial(struct i915_mmu_notifier *mmu) -{

• if (++mmu->serial == 0)

• mmu->serial = 1;
  

-}

-static void -i915_mmu_notifier_del(struct i915_mmu_notifier *mmu,

•       struct i915_mmu_object *mn)
  

-{

• lockdep_assert_held(&mmu->dev->struct_mutex);
• spin_lock(&mmu->lock);
• interval_tree_remove(&mn->it, &mmu->objects);
• __i915_mmu_notifier_update_serial(mmu);
• spin_unlock(&mmu->lock);
• /* Protected against _add() by dev->struct_mutex */
• if (--mmu->count == 0)

• __i915_mmu_notifier_destroy(mmu);
  

-}

-static int -i915_mmu_notifier_add(struct i915_mmu_notifier *mmu,

•       struct i915_mmu_object *mn)
  

-{

• struct interval_tree_node *it;
• int ret;
• ret = i915_mutex_lock_interruptible(mmu->dev);
• if (ret)

• return ret;
  

• /* Make sure we drop the final active reference (and thereby

• * remove the objects from the interval tree) before we do
  

• * the check for overlapping objects.
  

• */
  

• i915_gem_retire_requests(mmu->dev);
• /* Disallow overlapping userptr objects */
• spin_lock(&mmu->lock);
• it = interval_tree_iter_first(&mmu->objects,

• 		      mn->it.start, mn->it.last);
  

• if (it) {

• struct drm_i915_gem_object *obj;
  

• /* We only need to check the first object in the range as it
  

•  * either has cancelled gup work queued and we need to
  

•  * return back to the user to give time for the gup-workers
  

•  * to flush their object references upon which the object will
  

•  * be removed from the interval-tree, or the the range is
  

•  * still in use by another client and the overlap is invalid.
  

•  */
  

• obj = container_of(it, struct i915_mmu_object, it)->obj;
  

• ret = obj->userptr.workers ? -EAGAIN : -EINVAL;
  

• } else {

• interval_tree_insert(&mn->it, &mmu->objects);
  

• __i915_mmu_notifier_update_serial(mmu);
  

• ret = 0;
  

• }
• spin_unlock(&mmu->lock);
• mutex_unlock(&mmu->dev->struct_mutex);
• return ret;

-}

-static void -i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj) -{

• struct i915_mmu_object *mn;
• mn = obj->userptr.mn;
• if (mn == NULL)

• return;
  

• i915_mmu_notifier_del(mn->mmu, mn);
• obj->userptr.mn = NULL;

-}

-static int -i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,

• 		    unsigned flags)
  

-{

• struct i915_mmu_notifier *mmu;
• struct i915_mmu_object *mn;
• int ret;
• if (flags & I915_USERPTR_UNSYNCHRONIZED)

• return capable(CAP_SYS_ADMIN) ? 0 : -EPERM;
  

• down_write(&obj->userptr.mm->mmap_sem);
• ret = i915_mutex_lock_interruptible(obj->base.dev);
• if (ret == 0) {

• mmu = i915_mmu_notifier_get(obj->base.dev, obj->userptr.mm);
  

• if (!IS_ERR(mmu))
  

• 	mmu->count++; /* preemptive add to act as a refcount */
  

• else
  

• 	ret = PTR_ERR(mmu);
  

• mutex_unlock(&obj->base.dev->struct_mutex);
  

• }
• up_write(&obj->userptr.mm->mmap_sem);
• if (ret)

• return ret;
  

• mn = kzalloc(sizeof(*mn), GFP_KERNEL);
• if (mn == NULL) {

• ret = -ENOMEM;
  

• goto destroy_mmu;
  

• }
• mn->mmu = mmu;
• mn->it.start = obj->userptr.ptr;
• mn->it.last = mn->it.start + obj->base.size - 1;
• mn->obj = obj;
• ret = i915_mmu_notifier_add(mmu, mn);
• if (ret)

• goto free_mn;
  

• obj->userptr.mn = mn;
• return 0;

-free_mn:

• kfree(mn);

-destroy_mmu:

• mutex_lock(&obj->base.dev->struct_mutex);
• if (--mmu->count == 0)

• __i915_mmu_notifier_destroy(mmu);
  

• mutex_unlock(&obj->base.dev->struct_mutex);
• return ret;

-}

-#else

-static void -i915_gem_userptr_release__mmu_notifier(struct drm_i915_gem_object *obj) -{ -}

-static int -i915_gem_userptr_init__mmu_notifier(struct drm_i915_gem_object *obj,

• 		    unsigned flags)
  

-{

• if ((flags & I915_USERPTR_UNSYNCHRONIZED) == 0)

• return -ENODEV;
  

• if (!capable(CAP_SYS_ADMIN))

• return -EPERM;
  

• return 0;

-} -#endif

-struct get_pages_work {

• struct work_struct work;
• struct drm_i915_gem_object *obj;
• struct task_struct *task;

-};

-#if IS_ENABLED(CONFIG_SWIOTLB) -#define swiotlb_active() swiotlb_nr_tbl() -#else -#define swiotlb_active() 0 -#endif

-static int -st_set_pages(struct sg_table **st, struct page **pvec, int num_pages) -{

• struct scatterlist *sg;
• int ret, n;
• *st = kmalloc(sizeof(**st), GFP_KERNEL);
• if (*st == NULL)

• return -ENOMEM;
  

• if (swiotlb_active()) {

• ret = sg_alloc_table(*st, num_pages, GFP_KERNEL);
  

• if (ret)
  

• 	goto err;
  

• for_each_sg((*st)->sgl, sg, num_pages, n)
  

• 	sg_set_page(sg, pvec[n], PAGE_SIZE, 0);
  

• } else {

• ret = sg_alloc_table_from_pages(*st, pvec, num_pages,
  

• 				0, num_pages << PAGE_SHIFT,
  

• 				GFP_KERNEL);
  

• if (ret)
  

• 	goto err;
  

• }
• return 0;

-err:

• kfree(*st);
• *st = NULL;
• return ret;

-}

-static void -__i915_gem_userptr_get_pages_worker(struct work_struct *_work) -{

• struct get_pages_work *work = container_of(_work, typeof(*work), work);
• struct drm_i915_gem_object *obj = work->obj;
• struct drm_device *dev = obj->base.dev;
• const int num_pages = obj->base.size >> PAGE_SHIFT;
• struct page **pvec;
• int pinned, ret;
• ret = -ENOMEM;
• pinned = 0;
• pvec = kmalloc(num_pages*sizeof(struct page *),

•        GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
  

• if (pvec == NULL)

• pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
  

• if (pvec != NULL) {

• struct mm_struct *mm = obj->userptr.mm;
  

• down_read(&mm->mmap_sem);
  

• while (pinned < num_pages) {
  

• 	ret = get_user_pages(work->task, mm,
  

• 			     obj->userptr.ptr + pinned * PAGE_SIZE,
  

• 			     num_pages - pinned,
  

• 			     !obj->userptr.read_only, 0,
  

• 			     pvec + pinned, NULL);
  

• 	if (ret < 0)
  

• 		break;
  

• 	pinned += ret;
  

• }
  

• up_read(&mm->mmap_sem);
  

• }
• mutex_lock(&dev->struct_mutex);
• if (obj->userptr.work != &work->work) {

• ret = 0;
  

• } else if (pinned == num_pages) {

• ret = st_set_pages(&obj->pages, pvec, num_pages);
  

• if (ret == 0) {
  

• 	list_add_tail(&obj->global_list, &to_i915(dev)->mm.unbound_list);
  

• 	pinned = 0;
  

• }
  

• }
• obj->userptr.work = ERR_PTR(ret);
• obj->userptr.workers--;
• drm_gem_object_unreference(&obj->base);
• mutex_unlock(&dev->struct_mutex);
• release_pages(pvec, pinned, 0);
• drm_free_large(pvec);
• put_task_struct(work->task);
• kfree(work);

-}

-static int -i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj) -{

• const int num_pages = obj->base.size >> PAGE_SHIFT;
• struct page **pvec;
• int pinned, ret;
• /* If userspace should engineer that these pages are replaced in

• * the vma between us binding this page into the GTT and completion
  

• * of rendering... Their loss. If they change the mapping of their
  

• * pages they need to create a new bo to point to the new vma.
  

• *
  

• * However, that still leaves open the possibility of the vma
  

• * being copied upon fork. Which falls under the same userspace
  

• * synchronisation issue as a regular bo, except that this time
  

• * the process may not be expecting that a particular piece of
  

• * memory is tied to the GPU.
  

• *
  

• * Fortunately, we can hook into the mmu_notifier in order to
  

• * discard the page references prior to anything nasty happening
  

• * to the vma (discard or cloning) which should prevent the more
  

• * egregious cases from causing harm.
  

• */
  

• pvec = NULL;
• pinned = 0;
• if (obj->userptr.mm == current->mm) {

• pvec = kmalloc(num_pages*sizeof(struct page *),
  

• 	       GFP_TEMPORARY | __GFP_NOWARN | __GFP_NORETRY);
  

• if (pvec == NULL) {
  

• 	pvec = drm_malloc_ab(num_pages, sizeof(struct page *));
  

• 	if (pvec == NULL)
  

• 		return -ENOMEM;
  

• }
  

• pinned = __get_user_pages_fast(obj->userptr.ptr, num_pages,
  

• 			       !obj->userptr.read_only, pvec);
  

• }
• if (pinned < num_pages) {

• if (pinned < 0) {
  

• 	ret = pinned;
  

• 	pinned = 0;
  

• } else {
  

• 	/* Spawn a worker so that we can acquire the
  

• 	 * user pages without holding our mutex. Access
  

• 	 * to the user pages requires mmap_sem, and we have
  

• 	 * a strict lock ordering of mmap_sem, struct_mutex -
  

• 	 * we already hold struct_mutex here and so cannot
  

• 	 * call gup without encountering a lock inversion.
  

• 	 *
  

• 	 * Userspace will keep on repeating the operation
  

• 	 * (thanks to EAGAIN) until either we hit the fast
  

• 	 * path or the worker completes. If the worker is
  

• 	 * cancelled or superseded, the task is still run
  

• 	 * but the results ignored. (This leads to
  

• 	 * complications that we may have a stray object
  

• 	 * refcount that we need to be wary of when
  

• 	 * checking for existing objects during creation.)
  

• 	 * If the worker encounters an error, it reports
  

• 	 * that error back to this function through
  

• 	 * obj->userptr.work = ERR_PTR.
  

• 	 */
  

• 	ret = -EAGAIN;
  

• 	if (obj->userptr.work == NULL &&
  

• 	    obj->userptr.workers < I915_GEM_USERPTR_MAX_WORKERS) {
  

• 		struct get_pages_work *work;
  

• 		work = kmalloc(sizeof(*work), GFP_KERNEL);
  

• 		if (work != NULL) {
  

• 			obj->userptr.work = &work->work;
  

• 			obj->userptr.workers++;
  

• 			work->obj = obj;
  

• 			drm_gem_object_reference(&obj->base);
  

• 			work->task = current;
  

• 			get_task_struct(work->task);
  

• 			INIT_WORK(&work->work, __i915_gem_userptr_get_pages_worker);
  

• 			schedule_work(&work->work);
  

• 		} else
  

• 			ret = -ENOMEM;
  

• 	} else {
  

• 		if (IS_ERR(obj->userptr.work)) {
  

• 			ret = PTR_ERR(obj->userptr.work);
  

• 			obj->userptr.work = NULL;
  

• 		}
  

• 	}
  

• }
  

• } else {

• ret = st_set_pages(&obj->pages, pvec, num_pages);
  

• if (ret == 0) {
  

• 	obj->userptr.work = NULL;
  

• 	pinned = 0;
  

• }
  

• }
• release_pages(pvec, pinned, 0);
• drm_free_large(pvec);
• return ret;

-}

-static void -i915_gem_userptr_put_pages(struct drm_i915_gem_object *obj) -{

• struct scatterlist *sg;
• int i;
• BUG_ON(obj->userptr.work != NULL);
• if (obj->madv != I915_MADV_WILLNEED)

• obj->dirty = 0;
  

• for_each_sg(obj->pages->sgl, sg, obj->pages->nents, i) {

• struct page *page = sg_page(sg);
  

• if (obj->dirty)
  

• 	set_page_dirty(page);
  

• mark_page_accessed(page);
  

• page_cache_release(page);
  

• }
• obj->dirty = 0;
• sg_free_table(obj->pages);
• kfree(obj->pages);

-}

-static void -i915_gem_userptr_release(struct drm_i915_gem_object *obj) -{

• i915_gem_userptr_release__mmu_notifier(obj);
• if (obj->userptr.mm) {

• mmput(obj->userptr.mm);
  

• obj->userptr.mm = NULL;
  

• }

-}

-static int -i915_gem_userptr_dmabuf_export(struct drm_i915_gem_object *obj) -{

• if (obj->userptr.mn)

• return 0;
  

• return i915_gem_userptr_init__mmu_notifier(obj, 0);

-}

-static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {

• .dmabuf_export = i915_gem_userptr_dmabuf_export,
• .get_pages = i915_gem_userptr_get_pages,
• .put_pages = i915_gem_userptr_put_pages,
• .release = i915_gem_userptr_release,

-};

-/**

• • Creates a new mm object that wraps some normal memory from the process
• • context - user memory.
• • We impose several restrictions upon the memory being mapped
• • into the GPU.
• • 1. It must be page aligned (both start/end addresses, i.e ptr and size).
• • 2. It cannot overlap any other userptr object in the same address space.
• • 3. It must be normal system memory, not a pointer into another map of IO
• • space (e.g. it must not be a GTT mmapping of another object).
• • 4. We only allow a bo as large as we could in theory map into the GTT,
• • that is we limit the size to the total size of the GTT.
• • 5. The bo is marked as being snoopable. The backing pages are left
• • accessible directly by the CPU, but reads and writes by the GPU may
• • incur the cost of a snoop (unless you have an LLC architecture).
• • Synchronisation between multiple users and the GPU is left to userspace
• • through the normal set-domain-ioctl. The kernel will enforce that the
• • GPU relinquishes the VMA before it is returned back to the system
• • i.e. upon free(), munmap() or process termination. However, the userspace
• • malloc() library may not immediately relinquish the VMA after free() and
• • instead reuse it whilst the GPU is still reading and writing to the VMA.
• • Caveat emptor.
• • Also note, that the object created here is not currently a "first class"
• • object, in that several ioctls are banned. These are the CPU access
• • ioctls: mmap(), pwrite and pread. In practice, you are expected to use
• • direct access via your pointer rather than use those ioctls.
• • If you think this is a good interface to use to pass GPU memory between
• • drivers, please use dma-buf instead. In fact, wherever possible use
• • dma-buf instead.

+/* This ioctl was deemed as an heresy and was purified in its only acceptable

• • form.
  */

-int -i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file) -{

• struct drm_i915_private *dev_priv = dev->dev_private;
• struct drm_i915_gem_userptr *args = data;
• struct drm_i915_gem_object *obj;
• int ret;
• u32 handle;
• if (args->flags & ~(I915_USERPTR_READ_ONLY |

• 	    I915_USERPTR_UNSYNCHRONIZED))
  

• return -EINVAL;
  

• if (offset_in_page(args->user_ptr | args->user_size))

• return -EINVAL;
  

• if (args->user_size > dev_priv->gtt.base.total)

• return -E2BIG;
  

• if (!access_ok(args->flags & I915_USERPTR_READ_ONLY ? VERIFY_READ : VERIFY_WRITE,

•        (char __user *)(unsigned long)args->user_ptr, args->user_size))
  

• return -EFAULT;
  

• if (args->flags & I915_USERPTR_READ_ONLY) {

• /* On almost all of the current hw, we cannot tell the GPU that a
  

•  * page is readonly, so this is just a placeholder in the uAPI.
  

•  */
  

• return -ENODEV;
  

• }
• /* Allocate the new object */
• obj = i915_gem_object_alloc(dev);
• if (obj == NULL)

• return -ENOMEM;
  

• drm_gem_private_object_init(dev, &obj->base, args->user_size);
• i915_gem_object_init(obj, &i915_gem_userptr_ops);
• obj->cache_level = I915_CACHE_LLC;
• obj->base.write_domain = I915_GEM_DOMAIN_CPU;
• obj->base.read_domains = I915_GEM_DOMAIN_CPU;
• obj->userptr.ptr = args->user_ptr;
• obj->userptr.read_only = !!(args->flags & I915_USERPTR_READ_ONLY);
• /* And keep a pointer to the current->mm for resolving the user pages

• * at binding. This means that we need to hook into the mmu_notifier
  

• * in order to detect if the mmu is destroyed.
  

• */
  

• ret = -ENOMEM;
• if ((obj->userptr.mm = get_task_mm(current)))

• ret = i915_gem_userptr_init__mmu_notifier(obj, args->flags);
  

• if (ret == 0)

• ret = drm_gem_handle_create(file, &obj->base, &handle);
  

• /* drop reference from allocate - handle holds it now */
• drm_gem_object_unreference_unlocked(&obj->base);
• if (ret)

• return ret;
  

• args->handle = handle;
• return 0;

-}

-int -i915_gem_init_userptr(struct drm_device *dev) +int i915_gem_userptr_ioctl(struct drm_device *dev,

• 	   void *data, struct drm_file *file)
  

{ -#if defined(CONFIG_MMU_NOTIFIER)

• struct drm_i915_private *dev_priv = to_i915(dev);
• hash_init(dev_priv->mmu_notifiers);

-#endif

• return 0;

• return -EINVAL;

} diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c index 66cf417..b94aab7 100644 --- a/drivers/gpu/drm/i915/i915_gpu_error.c +++ b/drivers/gpu/drm/i915/i915_gpu_error.c @@ -205,7 +205,6 @@ static void print_error_buffers(struct drm_i915_error_state_buf *m, err_puts(m, tiling_flag(err->tiling)); err_puts(m, dirty_flag(err->dirty)); err_puts(m, purgeable_flag(err->purgeable));

• err_puts(m, err->userptr ? " userptr" : "");
  

  err_puts(m, err->ring != -1 ? " " : ""); err_puts(m, ring_str(err->ring)); err_puts(m, i915_cache_level_str(err->cache_level));

@@ -642,7 +641,6 @@ static void capture_bo(struct drm_i915_error_buffer *err, err->tiling = obj->tiling_mode; err->dirty = obj->dirty; err->purgeable = obj->madv != I915_MADV_WILLNEED;

• err->userptr = obj->userptr.mm != NULL; err->ring = obj->ring ? obj->ring->id : -1; err->cache_level = obj->cache_level;

}

1.8.3.1