Am 09.08.22 um 03:28 schrieb Chen Jeffy:
Hi Christian, On 8/9 星期二 2:03, Christian König wrote:Hi Jeffy, Am 08.08.22 um 05:51 schrieb Chen Jeffy:Hi Christian, Thanks for your reply, and sorry i didn't make it clear. On 8/8 星期一 0:52, Christian König wrote:Am 03.08.22 um 10:32 schrieb Jeffy Chen:Currently we are assuming a one to one mapping between dmabuf and handlewhen releasing GEM handles.But that is not always true, since we would create extra handles for theGEM obj in cases like gem_open() and getfb{,2}(). A similar issue was reported at:https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fall%2F20211105083308.392156-1-jay.xu%40rock-chips.com%2F&data=05%7C01%7Cchristian.koenig%40amd.com%7C52cd6ca16a3a415b92a708da79a67dec%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637956053232922419%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=hIuH18B10sbVAyS0D4iK6R6WYc%2BZ7mlxGcKdUae%2BW6Y%3D&reserved=0Another problem is that the drm_gem_remove_prime_handles() now onlyremove handle to the exported dmabuf (gem_obj->dma_buf), so the importedones would leak:WARNING: CPU: 2 PID: 236 at drivers/gpu/drm/drm_prime.c:228 drm_prime_destroy_file_private+0x18/0x24Let's fix these by using handle to find the exact map to remove.Well we are clearly something missing here. As far as I can see the current code is correct.Creating multiple GEM handles for the same DMA-buf is possible, but illegal. > In other words when a GEM handle is exported as DMA-buf and imported again you should intentionally always get the same handle.These issue are not about having handles for importing an exported dma-buf case, but for having multiple handles to a GEM object(which means having multiple handles to a dma-buf).I know the drm-prime is trying to make dma-buf and handle maps one to one, but the drm-gem is allowing to create extra handles for a GEM object, for example:drm_gem_open_ioctl -> drm_gem_handle_create_tail drm_mode_getfb2_ioctl -> drm_gem_handle_create drm_mode_getfb -> fb->funcs->create_handleYes, so far that's correct.So we are allowing GEM object to have multiple handles, and GEM object could have at most one dma-buf, doesn't that means that dma-buf could map to multiple handles?No, at least not for the same GEM file private. That's the reason why the rb is indexed by the dma_buf object and not the handle.In other words the rb is so that you have exactly one handle for each dma_buf in each file private.I don't think so, because if user get multiple handles for the same GEM obj and use drm_gem_prime_handle_to_fd() for those handles
Mhm, that works? This is illegal and should have been prevented somehow. Let me double check the code. Thanks for pointing that out, Christian.
, the current code would try to add multiple maps to rb: drm_prime_add_buf_handle(buf_1, hdl_1) drm_prime_add_buf_handle(buf_1, hdl_2) ... drm_prime_add_buf_handle(buf_1, hdl_n)Or should we rewrite the GEM framework to limit GEM object with uniq handle?No, the extra handles are expected because when you call drm_mode_getfb*() and drm_gem_open_ioctl() the caller now owns the returned GEM handle.The other issue is that we are leaking dma-buf <-> handle map for the imported dma-buf, since the drm_gem_remove_prime_handles doesn't take care of obj->import_attach->dmabuf.No, that's correct as well. obj->dma_buf is set even for imported DMA-buf objects. See drm_gem_prime_fd_to_handle().Well, that obj->dma_buf would be set in drm_gem_prime_fd_to_handle(create new handle), and cleared when releasing the latest handle(release handle).So it doesn't cover other handle creating path. For example, a imported dma buf:drm_gem_prime_fd_to_handle <-- we got a handle and obj->dma_buf and obj->import_attach->dmabufdrm_gem_handle_delete <-- we lost that handle and obj->dma_buf cleareddrm_gem_open_ioctl/or getfb* <-- we got a new handle and obj->import_attach->dmabuf drm_gem_handle_delete <-- we lost that handle and obj->dma_buf is null, which means rb leaks.Regards, Christian.But of cause this can be fixed in other way: +++ b/drivers/gpu/drm/drm_gem.c@@ -180,6 +180,9 @@ drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp)drm_prime_remove_buf_handle_locked(&filp->prime, obj->dma_buf); } + if (obj->import_attach) + drm_prime_remove_buf_handle_locked(&filp->prime, + obj->import_attach->dmabuf); mutex_unlock(&filp->prime.lock); }So this is pretty much a clear NAK to this patch since it shouldn't be necessary or something is seriously broken somewhere else.Regards, Christian.Signed-off-by: Jeffy Chen <jeffy.chen@xxxxxxxxxxxxxx> --- Changes in v2: Fix a typo of rbtree. drivers/gpu/drm/drm_gem.c | 17 +---------------- drivers/gpu/drm/drm_internal.h | 4 ++-- drivers/gpu/drm/drm_prime.c | 20 ++++++++++++-------- 3 files changed, 15 insertions(+), 26 deletions(-) diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c index eb0c2d041f13..ed39da383570 100644 --- a/drivers/gpu/drm/drm_gem.c +++ b/drivers/gpu/drm/drm_gem.c@@ -168,21 +168,6 @@ void drm_gem_private_object_init(struct drm_device *dev,} EXPORT_SYMBOL(drm_gem_private_object_init); -static void-drm_gem_remove_prime_handles(struct drm_gem_object *obj, struct drm_file *filp)-{ - /* - * Note: obj->dma_buf can't disappear as long as we still hold a - * handle reference in obj->handle_count. - */ - mutex_lock(&filp->prime.lock); - if (obj->dma_buf) { - drm_prime_remove_buf_handle_locked(&filp->prime, - obj->dma_buf); - } - mutex_unlock(&filp->prime.lock); -} - /*** drm_gem_object_handle_free - release resources bound to userspace handles* @obj: GEM object to clean up.@@ -253,7 +238,7 @@ drm_gem_object_release_handle(int id, void *ptr, void *data)if (obj->funcs->close) obj->funcs->close(obj, file_priv); - drm_gem_remove_prime_handles(obj, file_priv); + drm_prime_remove_buf_handle(&file_priv->prime, id); drm_vma_node_revoke(&obj->vma_node, file_priv); drm_gem_object_handle_put_unlocked(obj);diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.hindex 1fbbc19f1ac0..7bb98e6a446d 100644 --- a/drivers/gpu/drm/drm_internal.h +++ b/drivers/gpu/drm/drm_internal.h@@ -74,8 +74,8 @@ int drm_prime_fd_to_handle_ioctl(struct drm_device *dev, void *data, void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv); void drm_prime_destroy_file_private(struct drm_prime_file_private *prime_fpriv); -void drm_prime_remove_buf_handle_locked(struct drm_prime_file_private *prime_fpriv,- struct dma_buf *dma_buf);+void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv,+ uint32_t handle); /* drm_drv.c */ struct drm_minor *drm_minor_acquire(unsigned int minor_id);diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.cindex e3f09f18110c..bd5366b16381 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c@@ -190,29 +190,33 @@ static int drm_prime_lookup_buf_handle(struct drm_prime_file_private *prime_fprireturn -ENOENT; }-void drm_prime_remove_buf_handle_locked(struct drm_prime_file_private *prime_fpriv,- struct dma_buf *dma_buf)+void drm_prime_remove_buf_handle(struct drm_prime_file_private *prime_fpriv,+ uint32_t handle) { struct rb_node *rb; - rb = prime_fpriv->dmabufs.rb_node; + mutex_lock(&prime_fpriv->lock); + + rb = prime_fpriv->handles.rb_node; while (rb) { struct drm_prime_member *member; - member = rb_entry(rb, struct drm_prime_member, dmabuf_rb); - if (member->dma_buf == dma_buf) { + member = rb_entry(rb, struct drm_prime_member, handle_rb); + if (member->handle == handle) { rb_erase(&member->handle_rb, &prime_fpriv->handles); rb_erase(&member->dmabuf_rb, &prime_fpriv->dmabufs); - dma_buf_put(dma_buf); + dma_buf_put(member->dma_buf); kfree(member); - return; - } else if (member->dma_buf < dma_buf) { + break; + } else if (member->handle < handle) { rb = rb->rb_right; } else { rb = rb->rb_left; } } + + mutex_unlock(&prime_fpriv->lock); }void drm_prime_init_file_private(struct drm_prime_file_private *prime_fpriv)
