[Linaro-mm-sig] Re: [PATCH v1 2/6] drm/gem: Take reservation lock for vmap/vunmap operations

Am 15.07.22 um 02:52 schrieb Dmitry Osipenko:

The new common dma-buf locking convention will require buffer importers to hold the reservation lock around mapping operations. Make DRM GEM core to take the lock around the vmapping operations and update QXL and i915 drivers to use the locked functions for the case where DRM core now holds the lock. This patch prepares DRM core and drivers to transition to the common dma-buf locking convention where vmapping of exported GEMs will be done under the held reservation lock.

Oh ^^ That looks like a bug fix to me!

At least drm_gem_ttm_vmap() and drm_gem_ttm_vunmap() already expected that they are called with the reservation lock held.

Otherwise you could mess up internal structures in the TTM buffer object while vmapping it.

I will take a deeper look at this.

Regards, Christian.

Signed-off-by: Dmitry Osipenko dmitry.osipenko@collabora.com

drivers/gpu/drm/drm_client.c | 4 +-- drivers/gpu/drm/drm_gem.c | 28 ++++++++++++++++++++ drivers/gpu/drm/drm_gem_framebuffer_helper.c | 6 ++--- drivers/gpu/drm/drm_prime.c | 4 +-- drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 2 +- drivers/gpu/drm/qxl/qxl_object.c | 17 ++++++------ drivers/gpu/drm/qxl/qxl_prime.c | 4 +-- include/drm/drm_gem.h | 3 +++ 8 files changed, 50 insertions(+), 18 deletions(-)

diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c index 2b230b4d6942..fbcb1e995384 100644 --- a/drivers/gpu/drm/drm_client.c +++ b/drivers/gpu/drm/drm_client.c @@ -323,7 +323,7 @@ drm_client_buffer_vmap(struct drm_client_buffer *buffer, * fd_install step out of the driver backend hooks, to make that * final step optional for internal users. */

• ret = drm_gem_vmap(buffer->gem, map);

• ret = drm_gem_vmap_unlocked(buffer->gem, map); if (ret) return ret;

@@ -345,7 +345,7 @@ void drm_client_buffer_vunmap(struct drm_client_buffer *buffer) { struct iosys_map *map = &buffer->map;

• drm_gem_vunmap(buffer->gem, map);

• drm_gem_vunmap_unlocked(buffer->gem, map); } EXPORT_SYMBOL(drm_client_buffer_vunmap);

diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index eb0c2d041f13..9769c33cad99 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c @@ -1155,6 +1155,8 @@ void drm_gem_print_info(struct drm_printer *p, unsigned int indent, int drm_gem_pin(struct drm_gem_object *obj) {

• dma_resv_assert_held(obj->resv);
• if (obj->funcs->pin) return obj->funcs->pin(obj); else

@@ -1163,6 +1165,8 @@ int drm_gem_pin(struct drm_gem_object *obj) void drm_gem_unpin(struct drm_gem_object *obj) {

• dma_resv_assert_held(obj->resv);
• if (obj->funcs->unpin) obj->funcs->unpin(obj); }

@@ -1171,6 +1175,8 @@ int drm_gem_vmap(struct drm_gem_object *obj, struct iosys_map *map) { int ret;

• dma_resv_assert_held(obj->resv);
• if (!obj->funcs->vmap) return -EOPNOTSUPP;

@@ -1186,6 +1192,8 @@ EXPORT_SYMBOL(drm_gem_vmap); void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map) {

• dma_resv_assert_held(obj->resv);
• if (iosys_map_is_null(map)) return;

@@ -1197,6 +1205,26 @@ void drm_gem_vunmap(struct drm_gem_object *obj, struct iosys_map *map) } EXPORT_SYMBOL(drm_gem_vunmap); +int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map) +{

• int ret;
• dma_resv_lock(obj->resv, NULL);
• ret = drm_gem_vmap(obj, map);
• dma_resv_unlock(obj->resv);
• return ret;

+} +EXPORT_SYMBOL(drm_gem_vmap_unlocked);

+void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map) +{

• dma_resv_lock(obj->resv, NULL);
• drm_gem_vunmap(obj, map);
• dma_resv_unlock(obj->resv);

+} +EXPORT_SYMBOL(drm_gem_vunmap_unlocked);

• /**
  • drm_gem_lock_reservations - Sets up the ww context and acquires
  • the lock on an array of GEM objects.

diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c index 880a4975507f..e35e224e6303 100644 --- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c +++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c @@ -354,7 +354,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map, ret = -EINVAL; goto err_drm_gem_vunmap; }

• ret = drm_gem_vmap(obj, &map[i]);
  

• ret = drm_gem_vmap_unlocked(obj, &map[i]);
  

  if (ret) goto err_drm_gem_vunmap; }

@@ -376,7 +376,7 @@ int drm_gem_fb_vmap(struct drm_framebuffer *fb, struct iosys_map *map, obj = drm_gem_fb_get_obj(fb, i); if (!obj) continue;

• drm_gem_vunmap(obj, &map[i]);
  

• drm_gem_vunmap_unlocked(obj, &map[i]);
  

  } return ret; }

@@ -403,7 +403,7 @@ void drm_gem_fb_vunmap(struct drm_framebuffer *fb, struct iosys_map *map) continue; if (iosys_map_is_null(&map[i])) continue;

• drm_gem_vunmap(obj, &map[i]);
  

• drm_gem_vunmap_unlocked(obj, &map[i]);
  

  } } EXPORT_SYMBOL(drm_gem_fb_vunmap);

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index b75ef1756873..1bd234fd21a5 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -678,7 +678,7 @@ int drm_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct iosys_map *map) { struct drm_gem_object *obj = dma_buf->priv;

• return drm_gem_vmap(obj, map);

• return drm_gem_vmap_unlocked(obj, map); } EXPORT_SYMBOL(drm_gem_dmabuf_vmap);

@@ -694,7 +694,7 @@ void drm_gem_dmabuf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map) { struct drm_gem_object *obj = dma_buf->priv;

• drm_gem_vunmap(obj, map);

• drm_gem_vunmap_unlocked(obj, map); } EXPORT_SYMBOL(drm_gem_dmabuf_vunmap);

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c index 5ecea7df98b1..cc54a5b1d6ae 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c @@ -72,7 +72,7 @@ static int i915_gem_dmabuf_vmap(struct dma_buf *dma_buf, struct drm_i915_gem_object *obj = dma_buf_to_obj(dma_buf); void *vaddr;

• vaddr = i915_gem_object_pin_map_unlocked(obj, I915_MAP_WB);

• vaddr = i915_gem_object_pin_map(obj, I915_MAP_WB); if (IS_ERR(vaddr)) return PTR_ERR(vaddr);

diff --git a/drivers/gpu/drm/qxl/qxl_object.c b/drivers/gpu/drm/qxl/qxl_object.c index 695d9308d1f0..06a58dad5f5c 100644 --- a/drivers/gpu/drm/qxl/qxl_object.c +++ b/drivers/gpu/drm/qxl/qxl_object.c @@ -168,9 +168,16 @@ int qxl_bo_vmap_locked(struct qxl_bo *bo, struct iosys_map *map) bo->map_count++; goto out; }

• r = ttm_bo_vmap(&bo->tbo, &bo->map);

• r = __qxl_bo_pin(bo); if (r) return r;
• r = ttm_bo_vmap(&bo->tbo, &bo->map);
• if (r) {

• __qxl_bo_unpin(bo);
  

• return r;
  

• } bo->map_count = 1;

/* TODO: Remove kptr in favor of map everywhere. */ @@ -192,12 +199,6 @@ int qxl_bo_vmap(struct qxl_bo *bo, struct iosys_map *map) if (r) return r;

• r = __qxl_bo_pin(bo);
• if (r) {

• qxl_bo_unreserve(bo);
  

• return r;
  

• }
• r = qxl_bo_vmap_locked(bo, map); qxl_bo_unreserve(bo); return r;

@@ -247,6 +248,7 @@ void qxl_bo_vunmap_locked(struct qxl_bo *bo) return; bo->kptr = NULL; ttm_bo_vunmap(&bo->tbo, &bo->map);

• __qxl_bo_unpin(bo); }

int qxl_bo_vunmap(struct qxl_bo *bo) @@ -258,7 +260,6 @@ int qxl_bo_vunmap(struct qxl_bo *bo) return r; qxl_bo_vunmap_locked(bo);

• __qxl_bo_unpin(bo); qxl_bo_unreserve(bo); return 0; }

diff --git a/drivers/gpu/drm/qxl/qxl_prime.c b/drivers/gpu/drm/qxl/qxl_prime.c index 142d01415acb..9169c26357d3 100644 --- a/drivers/gpu/drm/qxl/qxl_prime.c +++ b/drivers/gpu/drm/qxl/qxl_prime.c @@ -59,7 +59,7 @@ int qxl_gem_prime_vmap(struct drm_gem_object *obj, struct iosys_map *map) struct qxl_bo *bo = gem_to_qxl_bo(obj); int ret;

• ret = qxl_bo_vmap(bo, map);

• ret = qxl_bo_vmap_locked(bo, map); if (ret < 0) return ret;

@@ -71,5 +71,5 @@ void qxl_gem_prime_vunmap(struct drm_gem_object *obj, { struct qxl_bo *bo = gem_to_qxl_bo(obj);

• qxl_bo_vunmap(bo);

• qxl_bo_vunmap_locked(bo); }

diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h index 87cffc9efa85..bf3700415229 100644 --- a/include/drm/drm_gem.h +++ b/include/drm/drm_gem.h @@ -420,4 +420,7 @@ void drm_gem_unlock_reservations(struct drm_gem_object **objs, int count, int drm_gem_dumb_map_offset(struct drm_file *file, struct drm_device *dev, u32 handle, u64 *offset); +int drm_gem_vmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map); +void drm_gem_vunmap_unlocked(struct drm_gem_object *obj, struct iosys_map *map);

• #endif /* __DRM_GEM_H__ */