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Commit 71bb23c7 authored by Chris Wilson's avatar Chris Wilson Committed by Daniel Vetter
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drm/vgem: Pin our pages for dmabuf exports 



When the caller maps their dmabuf and we return an sg_table, the caller
doesn't expect the pages beneath that sg_table to vanish on a whim (i.e.
under mempressure). The contract is that the pages are pinned for the
duration of the mapping (from dma_buf_map_attachment() to
dma_buf_unmap_attachment). To comply, we need to introduce our own
vgem_object.pages_pin_count and elevate it across the mapping. However,
the drm_prime interface we use calls drv->prime_pin on dma_buf_attach
and drv->prime_unpin on dma_buf_detach, which while that does cover the
mapping is much broader than is desired -- but it will do for now.

v2: also hold the pin across prime_vmap/vunmap

Reported-by: default avatarTomi Sarvela <tomi.p.sarvela@intel.com>
Testcase: igt/gem_concurrent_blit/*swap*vgem*
Fixes: 5ba6c9ff ("drm/vgem: Fix mmaping")
Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Sean Paul <seanpaul@chromium.org>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: <stable@vger.kernel.org> # needs a backport
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20170622134617.17912-1-chris@chris-wilson.co.uk
parent 2bf5ccc2

drivers/gpu/drm/vgem/vgem_drv.c

+60 −21
Original line number Diff line number Diff line
@@ -52,6 +52,7 @@ static void vgem_gem_free_object(struct drm_gem_object *obj) 
	struct drm_vgem_gem_object *vgem_obj = to_vgem_bo(obj);



	kvfree(vgem_obj->pages);

	mutex_destroy(&vgem_obj->pages_lock);



	if (obj->import_attach)

		drm_prime_gem_destroy(obj, vgem_obj->table);
@@ -76,11 +77,15 @@ static int vgem_gem_fault(struct vm_fault *vmf) 
	if (page_offset > num_pages)

		return VM_FAULT_SIGBUS;



	ret = -ENOENT;

	mutex_lock(&obj->pages_lock);

	if (obj->pages) {

		get_page(obj->pages[page_offset]);

		vmf->page = obj->pages[page_offset];

		ret = 0;

	} else {

	}

	mutex_unlock(&obj->pages_lock);

	if (ret) {

		struct page *page;



		page = shmem_read_mapping_page(
@@ -161,6 +166,8 @@ static struct drm_vgem_gem_object *__vgem_gem_create(struct drm_device *dev, 
		return ERR_PTR(ret);

	}



	mutex_init(&obj->pages_lock);



	return obj;

}
@@ -274,37 +281,66 @@ static const struct file_operations vgem_driver_fops = { 
	.release	= drm_release,

};



static struct page **vgem_pin_pages(struct drm_vgem_gem_object *bo)

{

	mutex_lock(&bo->pages_lock);

	if (bo->pages_pin_count++ == 0) {

		struct page **pages;



		pages = drm_gem_get_pages(&bo->base);

		if (IS_ERR(pages)) {

			bo->pages_pin_count--;

			mutex_unlock(&bo->pages_lock);

			return pages;

		}



		bo->pages = pages;

	}

	mutex_unlock(&bo->pages_lock);



	return bo->pages;

}



static void vgem_unpin_pages(struct drm_vgem_gem_object *bo)

{

	mutex_lock(&bo->pages_lock);

	if (--bo->pages_pin_count == 0) {

		drm_gem_put_pages(&bo->base, bo->pages, true, true);

		bo->pages = NULL;

	}

	mutex_unlock(&bo->pages_lock);

}



static int vgem_prime_pin(struct drm_gem_object *obj)

{

	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);

	long n_pages = obj->size >> PAGE_SHIFT;

	struct page **pages;



	/* Flush the object from the CPU cache so that importers can rely

	 * on coherent indirect access via the exported dma-address.

	 */

	pages = drm_gem_get_pages(obj);

	pages = vgem_pin_pages(bo);

	if (IS_ERR(pages))

		return PTR_ERR(pages);



	/* Flush the object from the CPU cache so that importers can rely

	 * on coherent indirect access via the exported dma-address.

	 */

	drm_clflush_pages(pages, n_pages);

	drm_gem_put_pages(obj, pages, true, false);



	return 0;

}



static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)

static void vgem_prime_unpin(struct drm_gem_object *obj)

{

	struct sg_table *st;

	struct page **pages;

	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);



	pages = drm_gem_get_pages(obj);

	if (IS_ERR(pages))

		return ERR_CAST(pages);

	vgem_unpin_pages(bo);

}



	st = drm_prime_pages_to_sg(pages, obj->size >> PAGE_SHIFT);

	drm_gem_put_pages(obj, pages, false, false);

static struct sg_table *vgem_prime_get_sg_table(struct drm_gem_object *obj)

{

	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);



	return st;

	return drm_prime_pages_to_sg(bo->pages, bo->base.size >> PAGE_SHIFT);

}



static struct drm_gem_object* vgem_prime_import(struct drm_device *dev,
@@ -333,6 +369,8 @@ static struct drm_gem_object *vgem_prime_import_sg_table(struct drm_device *dev, 
		__vgem_gem_destroy(obj);

		return ERR_PTR(-ENOMEM);

	}



	obj->pages_pin_count++; /* perma-pinned */

	drm_prime_sg_to_page_addr_arrays(obj->table, obj->pages, NULL,

					npages);

	return &obj->base;
@@ -340,23 +378,23 @@ static struct drm_gem_object *vgem_prime_import_sg_table(struct drm_device *dev, 


static void *vgem_prime_vmap(struct drm_gem_object *obj)

{

	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);

	long n_pages = obj->size >> PAGE_SHIFT;

	struct page **pages;

	void *addr;



	pages = drm_gem_get_pages(obj);

	pages = vgem_pin_pages(bo);

	if (IS_ERR(pages))

		return NULL;



	addr = vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL));

	drm_gem_put_pages(obj, pages, false, false);



	return addr;

	return vmap(pages, n_pages, 0, pgprot_writecombine(PAGE_KERNEL));

}



static void vgem_prime_vunmap(struct drm_gem_object *obj, void *vaddr)

{

	struct drm_vgem_gem_object *bo = to_vgem_bo(obj);



	vunmap(vaddr);

	vgem_unpin_pages(bo);

}



static int vgem_prime_mmap(struct drm_gem_object *obj,
@@ -409,6 +447,7 @@ static struct drm_driver vgem_driver = { 
	.prime_handle_to_fd = drm_gem_prime_handle_to_fd,

	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,

	.gem_prime_pin = vgem_prime_pin,

	.gem_prime_unpin = vgem_prime_unpin,

	.gem_prime_import = vgem_prime_import,

	.gem_prime_export = drm_gem_prime_export,

	.gem_prime_import_sg_table = vgem_prime_import_sg_table,

drivers/gpu/drm/vgem/vgem_drv.h

+4 −0
Original line number Diff line number Diff line
@@ -43,7 +43,11 @@ struct vgem_file { 
#define to_vgem_bo(x) container_of(x, struct drm_vgem_gem_object, base)

struct drm_vgem_gem_object {

	struct drm_gem_object base;



	struct page **pages;

	unsigned int pages_pin_count;

	struct mutex pages_lock;



	struct sg_table *table;

};