-----Original Message----- From: dri-devel dri-devel-bounces@lists.freedesktop.org On Behalf Of Thomas Zimmermann Sent: Friday, January 8, 2021 4:43 AM To: sumit.semwal@linaro.org; christian.koenig@amd.com; airlied@redhat.com; daniel@ffwll.ch; maarten.lankhorst@linux.intel.com; mripard@kernel.org; kraxel@redhat.com; hdegoede@redhat.com; sean@poorly.run; eric@anholt.net; sam@ravnborg.org Cc: Daniel Vetter daniel.vetter@ffwll.ch; dri-devel@lists.freedesktop.org; virtualization@lists.linux-foundation.org; linaro-mm-sig@lists.linaro.org; Thomas Zimmermann tzimmermann@suse.de; linux- media@vger.kernel.org Subject: [PATCH v4 01/13] dma-buf: Add vmap_local and vnumap_local operations

The existing dma-buf calls dma_buf_vmap() and dma_buf_vunmap() are allowed to pin the buffer or acquire the buffer's reservation object lock.

This is a problem for callers that only require a short-term mapping of the buffer without the pinning, or callers that have special locking requirements. These may suffer from unnecessary overhead or interfere with regular pin operations.

The new interfaces dma_buf_vmap_local(), dma_buf_vunmapo_local(), and their rsp callbacks in struct dma_buf_ops provide an alternative without pinning or reservation locking. Callers are responsible for these operations.

v4:

• update documentation (Daniel)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch

---

drivers/dma-buf/dma-buf.c | 81 +++++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 34 ++++++++++++++++ 2 files changed, 115 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index b8465243eca2..01f9c74d97fa 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -1295,6 +1295,87 @@ void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map) } EXPORT_SYMBOL_GPL(dma_buf_vunmap);

+/**

• • dma_buf_vmap_local - Create virtual mapping for the buffer object into

kernel

• • address space.
• • @dmabuf: [in] buffer to vmap
• • @map: [out] returns the vmap pointer
• • Unlike dma_buf_vmap() this is a short term mapping and will not pin
• • the buffer. The struct dma_resv for the @dmabuf must be locked until
• • dma_buf_vunmap_local() is called.
• • Returns:
• • 0 on success, or a negative errno code otherwise.
• */

+int dma_buf_vmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map) +{

• struct dma_buf_map ptr;
• int ret = 0;
• dma_buf_map_clear(map);
• if (WARN_ON(!dmabuf))

• return -EINVAL;
  

• dma_resv_assert_held(dmabuf->resv);
• if (!dmabuf->ops->vmap_local)

• return -EINVAL;
  

You are clearing the map, and then doing the above checks.

Is it ok to change the map info and then exit on error?

Mike

• mutex_lock(&dmabuf->lock);
• if (dmabuf->vmapping_counter) {

• dmabuf->vmapping_counter++;
  

• BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
  

• *map = dmabuf->vmap_ptr;
  

• goto out_unlock;
  

• }
• BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
• ret = dmabuf->ops->vmap_local(dmabuf, &ptr);
• if (WARN_ON_ONCE(ret))

• goto out_unlock;
  

• dmabuf->vmap_ptr = ptr;
• dmabuf->vmapping_counter = 1;
• *map = dmabuf->vmap_ptr;

+out_unlock:

• mutex_unlock(&dmabuf->lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(dma_buf_vmap_local);

+/**

• • dma_buf_vunmap_local - Unmap a vmap obtained by

dma_buf_vmap_local.

• • @dmabuf: [in] buffer to vunmap
• • @map: [in] vmap pointer to vunmap
• • Release a mapping established with dma_buf_vmap_local().
• */

+void dma_buf_vunmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map) +{

• if (WARN_ON(!dmabuf))

• return;
  

• dma_resv_assert_held(dmabuf->resv);
• BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
• BUG_ON(dmabuf->vmapping_counter == 0);
• BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
• mutex_lock(&dmabuf->lock);
• if (--dmabuf->vmapping_counter == 0) {

• if (dmabuf->ops->vunmap_local)
  

• 	dmabuf->ops->vunmap_local(dmabuf, map);
  

• dma_buf_map_clear(&dmabuf->vmap_ptr);
  

• }
• mutex_unlock(&dmabuf->lock);

+} +EXPORT_SYMBOL_GPL(dma_buf_vunmap_local);

#ifdef CONFIG_DEBUG_FS static int dma_buf_debug_show(struct seq_file *s, void *unused) { diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 628681bf6c99..aeed754b5467 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -264,6 +264,38 @@ struct dma_buf_ops {

int (*vmap)(struct dma_buf *dmabuf, struct dma_buf_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);

• /**

• * @vmap_local:
  

• *
  

• * Creates a virtual mapping for the buffer into kernel address space.
  

• *
  

• * This callback establishes short-term mappings for situations where
  

• * callers only use the buffer for a bounded amount of time; such as
  

• * updates to the framebuffer or reading back contained information.
  

• * In contrast to the regular @vmap callback, vmap_local does never
  

pin

• * the buffer to a specific domain or acquire the buffer's reservation
  

• * lock.
  

• *
  

• * This is called with the &dma_buf.resv object locked. Callers must
  

hold

• * the lock until after removing the mapping with @vunmap_local.
  

• *
  

• * This callback is optional.
  

• *
  

• * Returns:
  

• *
  

• * 0 on success or a negative error code on failure.
  

• */
  

• int (*vmap_local)(struct dma_buf *dmabuf, struct dma_buf_map

*map);

• /**

• * @vunmap_local:
  

• *
  

• * Removes a virtual mapping that was established by @vmap_local.
  

• *
  

• * This callback is optional.
  

• */
  

• void (*vunmap_local)(struct dma_buf *dmabuf, struct dma_buf_map

*map); };

/** @@ -501,4 +533,6 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *, unsigned long); int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map); void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map); +int dma_buf_vmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map); +void dma_buf_vunmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map);

#endif /* __DMA_BUF_H__ */

2.29.2

---

dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

-----Original Message----- From: dri-devel dri-devel-bounces@lists.freedesktop.org On Behalf Of Thomas Zimmermann Sent: Tuesday, January 12, 2021 2:45 AM To: Ruhl, Michael J michael.j.ruhl@intel.com; sumit.semwal@linaro.org; christian.koenig@amd.com; airlied@redhat.com; daniel@ffwll.ch; maarten.lankhorst@linux.intel.com; mripard@kernel.org; kraxel@redhat.com; hdegoede@redhat.com; sean@poorly.run; eric@anholt.net; sam@ravnborg.org Cc: linaro-mm-sig@lists.linaro.org; Daniel Vetter daniel.vetter@ffwll.ch; virtualization@lists.linux-foundation.org; dri-devel@lists.freedesktop.org; linux-media@vger.kernel.org Subject: Re: [PATCH v4 01/13] dma-buf: Add vmap_local and vnumap_local operations

Hi

Am 08.01.21 um 17:12 schrieb Ruhl, Michael J:

...

...

-----Original Message----- From: dri-devel dri-devel-bounces@lists.freedesktop.org On Behalf Of Thomas Zimmermann Sent: Friday, January 8, 2021 4:43 AM To: sumit.semwal@linaro.org; christian.koenig@amd.com; airlied@redhat.com; daniel@ffwll.ch; maarten.lankhorst@linux.intel.com; mripard@kernel.org; kraxel@redhat.com; hdegoede@redhat.com; sean@poorly.run; eric@anholt.net; sam@ravnborg.org Cc: Daniel Vetter daniel.vetter@ffwll.ch; dri-

devel@lists.freedesktop.org;

...

...

virtualization@lists.linux-foundation.org; linaro-mm-sig@lists.linaro.org; Thomas Zimmermann tzimmermann@suse.de; linux- media@vger.kernel.org Subject: [PATCH v4 01/13] dma-buf: Add vmap_local and vnumap_local operations

The existing dma-buf calls dma_buf_vmap() and dma_buf_vunmap() are allowed to pin the buffer or acquire the buffer's reservation object lock.

This is a problem for callers that only require a short-term mapping of the buffer without the pinning, or callers that have special locking requirements. These may suffer from unnecessary overhead or interfere with regular pin operations.

The new interfaces dma_buf_vmap_local(), dma_buf_vunmapo_local(),

and

...

...

their rsp callbacks in struct dma_buf_ops provide an alternative without pinning or reservation locking. Callers are responsible for these operations.

v4:

• update documentation (Daniel)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch

---

drivers/dma-buf/dma-buf.c | 81 +++++++++++++++++++++++++++++++++++++++ include/linux/dma-buf.h | 34 ++++++++++++++++ 2 files changed, 115 insertions(+)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index b8465243eca2..01f9c74d97fa 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -1295,6 +1295,87 @@ void dma_buf_vunmap(struct dma_buf

*dmabuf,

...

...

struct dma_buf_map *map) } EXPORT_SYMBOL_GPL(dma_buf_vunmap);

+/**

• • dma_buf_vmap_local - Create virtual mapping for the buffer object

into

...

...

kernel

• • address space.
• • @dmabuf: [in] buffer to vmap
• • @map: [out] returns the vmap pointer
• • Unlike dma_buf_vmap() this is a short term mapping and will not pin
• • the buffer. The struct dma_resv for the @dmabuf must be locked until
• • dma_buf_vunmap_local() is called.
• • Returns:
• • 0 on success, or a negative errno code otherwise.
• */

+int dma_buf_vmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map) +{

• struct dma_buf_map ptr;
• int ret = 0;
• dma_buf_map_clear(map);
• if (WARN_ON(!dmabuf))

• return -EINVAL;
  

• dma_resv_assert_held(dmabuf->resv);
• if (!dmabuf->ops->vmap_local)

• return -EINVAL;
  

You are clearing the map, and then doing the above checks.

Is it ok to change the map info and then exit on error?

In vmap_local map argument returns the mapping's address. Callers are expected to check the return code. But I would expect a careless caller to not check, or check for map being cleared. Clearing it here first is the save thing to do.

Ahh, a pre-emptive attempt to make sure the caller doesn't cause more problems on error. 😊

Thanks,

M

Best regards Thomas

...

Mike

...

• mutex_lock(&dmabuf->lock);
• if (dmabuf->vmapping_counter) {

• dmabuf->vmapping_counter++;
  

• BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
  

• *map = dmabuf->vmap_ptr;
  

• goto out_unlock;
  

• }
• BUG_ON(dma_buf_map_is_set(&dmabuf->vmap_ptr));
• ret = dmabuf->ops->vmap_local(dmabuf, &ptr);
• if (WARN_ON_ONCE(ret))

• goto out_unlock;
  

• dmabuf->vmap_ptr = ptr;
• dmabuf->vmapping_counter = 1;
• *map = dmabuf->vmap_ptr;

+out_unlock:

• mutex_unlock(&dmabuf->lock);
• return ret;

+} +EXPORT_SYMBOL_GPL(dma_buf_vmap_local);

+/**

• • dma_buf_vunmap_local - Unmap a vmap obtained by

dma_buf_vmap_local.

• • @dmabuf: [in] buffer to vunmap
• • @map: [in] vmap pointer to vunmap
• • Release a mapping established with dma_buf_vmap_local().
• */

+void dma_buf_vunmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map) +{

• if (WARN_ON(!dmabuf))

• return;
  

• dma_resv_assert_held(dmabuf->resv);
• BUG_ON(dma_buf_map_is_null(&dmabuf->vmap_ptr));
• BUG_ON(dmabuf->vmapping_counter == 0);
• BUG_ON(!dma_buf_map_is_equal(&dmabuf->vmap_ptr, map));
• mutex_lock(&dmabuf->lock);
• if (--dmabuf->vmapping_counter == 0) {

• if (dmabuf->ops->vunmap_local)
  

• 	dmabuf->ops->vunmap_local(dmabuf, map);
  

• dma_buf_map_clear(&dmabuf->vmap_ptr);
  

• }
• mutex_unlock(&dmabuf->lock);

+} +EXPORT_SYMBOL_GPL(dma_buf_vunmap_local);

#ifdef CONFIG_DEBUG_FS static int dma_buf_debug_show(struct seq_file *s, void *unused) { diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index 628681bf6c99..aeed754b5467 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -264,6 +264,38 @@ struct dma_buf_ops {

int (*vmap)(struct dma_buf *dmabuf, struct dma_buf_map *map); void (*vunmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);

• /**

• * @vmap_local:
  

• *
  

• * Creates a virtual mapping for the buffer into kernel address space.
  

• *
  

• * This callback establishes short-term mappings for situations where
  

• * callers only use the buffer for a bounded amount of time; such as
  

• * updates to the framebuffer or reading back contained information.
  

• * In contrast to the regular @vmap callback, vmap_local does never
  

pin

• * the buffer to a specific domain or acquire the buffer's reservation
  

• * lock.
  

• *
  

• * This is called with the &dma_buf.resv object locked. Callers must
  

hold

• * the lock until after removing the mapping with @vunmap_local.
  

• *
  

• * This callback is optional.
  

• *
  

• * Returns:
  

• *
  

• * 0 on success or a negative error code on failure.
  

• */
  

• int (*vmap_local)(struct dma_buf *dmabuf, struct dma_buf_map

*map);

• /**

• * @vunmap_local:
  

• *
  

• * Removes a virtual mapping that was established by @vmap_local.
  

• *
  

• * This callback is optional.
  

• */
  

• void (*vunmap_local)(struct dma_buf *dmabuf, struct dma_buf_map

*map); };

/** @@ -501,4 +533,6 @@ int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *, unsigned long); int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map

*map);

...

...

void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map); +int dma_buf_vmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map); +void dma_buf_vunmap_local(struct dma_buf *dmabuf, struct dma_buf_map *map);

#endif /* __DMA_BUF_H__ */

2.29.2

---

dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

---

dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer

On Fri, Jan 08, 2021 at 10:43:31AM +0100, Thomas Zimmermann wrote:

Implementations of the vmap/vunmap GEM callbacks may perform pinning of the BO and may acquire the associated reservation object's lock. Callers that only require a mapping of the contained memory can thus interfere with other tasks that require exact pinning, such as scanout. This is less of an issue with private SHMEM buffers, but may happen with imported ones.

Therefore provide the new interfaces drm_gem_shmem_vmap_local() and drm_gem_shmem_vunmap_local(), which only perform the vmap/vunmap operations. Callers have to hold the reservation lock while the mapping persists.

This patch also connects GEM SHMEM helpers to GEM object functions with equivalent functionality.

v4:

• call dma_buf_{vmap,vunmap}_local() where necessary (Daniel)
• move driver changes into separate patches (Daniel)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

drivers/gpu/drm/drm_gem_shmem_helper.c | 90 +++++++++++++++++++++++--- include/drm/drm_gem_shmem_helper.h | 2 + 2 files changed, 84 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 9825c378dfa6..298832b2b43b 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -32,6 +32,8 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs = { .get_sg_table = drm_gem_shmem_get_sg_table, .vmap = drm_gem_shmem_vmap, .vunmap = drm_gem_shmem_vunmap,

• .vmap_local = drm_gem_shmem_vmap_local,
• .vunmap_local = drm_gem_shmem_vunmap_local, .mmap = drm_gem_shmem_mmap,

};

@@ -261,7 +263,8 @@ void drm_gem_shmem_unpin(struct drm_gem_object *obj) } EXPORT_SYMBOL(drm_gem_shmem_unpin);

-static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map) +static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map,

• 		     bool local)
  

This is a bit spaghetti and also has the problem that we're not changing shmem->vmap_use_count under different locks, depending upon which path we're taking.

I think the cleanest would be if we pull the if (import_attach) case out of the _locked() version completely, for all cases, and also outside of the shmem->vmap_lock. This means no caching of vmaps in the shmem layer anymore for imported buffers, but this is no longer a problem: We cache them in the exporters instead (I think at least, if not maybe need to fix that where it's expensive).

Other option would be to unly pull it out for the _vmap_local case, but that's a bit ugly because no longer symmetrical in the various paths.

{ struct drm_gem_object *obj = &shmem->base; int ret = 0; @@ -272,7 +275,10 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct }

if (obj->import_attach) {

• ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	ret = dma_buf_vmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

  if (!ret) { if (WARN_ON(map->is_iomem)) { ret = -EIO;

@@ -313,7 +319,7 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct return ret; }

-/* +/**

• drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
• @shmem: shmem GEM object
• @map: Returns the kernel virtual address of the SHMEM GEM object's backing

@@ -339,15 +345,53 @@ int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map) ret = mutex_lock_interruptible(&shmem->vmap_lock); if (ret) return ret;

• ret = drm_gem_shmem_vmap_locked(shmem, map);

• ret = drm_gem_shmem_vmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock);

  return ret;

} EXPORT_SYMBOL(drm_gem_shmem_vmap);

+/**

• • drm_gem_shmem_vmap_local - Create a virtual mapping for a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Returns the kernel virtual address of the SHMEM GEM object's backing

• •   store.
    

• • This function makes sure that a contiguous kernel virtual address mapping
• • exists for the buffer backing the shmem GEM object.
• • The function is called with the BO's reservation object locked. Callers must
• • hold the lock until after unmapping the buffer.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local. But
• • it can also be called by drivers directly, in which case it will hide the
• • differences between dma-buf imported and natively allocated objects.

So for the other callbacks I tried to make sure we have different entry points for this, since it's not really the same thing and because of the locking mess we have with dma_resv_lock vs various pre-existing local locking scheme, it's easy to get a mess.

I think the super clean version here would be to also export just the internal stuff for the ->v(un)map_local hooks, but that's maybe a bit too much boilerplate for no real gain. -Daniel

• • Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_local().
• • Returns:
• • 0 on success or a negative error code on failure.
• */

+int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• int ret;
• dma_resv_assert_held(obj->resv);
• ret = mutex_lock_interruptible(&shmem->vmap_lock);
• if (ret)

• return ret;
  

• ret = drm_gem_shmem_vmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);
• return ret;

+} +EXPORT_SYMBOL(drm_gem_shmem_vmap_local);

static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,

• 			struct dma_buf_map *map)
  

• 			struct dma_buf_map *map, bool local)
  

{ struct drm_gem_object *obj = &shmem->base;

@@ -358,7 +402,10 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, return;

if (obj->import_attach)

• dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	dma_buf_vunmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

  else vunmap(shmem->vaddr);

@@ -366,7 +413,7 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, drm_gem_shmem_put_pages(shmem); }

-/* +/**

• drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
• @shmem: shmem GEM object
• @map: Kernel virtual address where the SHMEM GEM object was mapped

@@ -384,11 +431,38 @@ void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map) struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);

mutex_lock(&shmem->vmap_lock);

• drm_gem_shmem_vunmap_locked(shmem, map);

• drm_gem_shmem_vunmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock);

} EXPORT_SYMBOL(drm_gem_shmem_vunmap);

+/**

• • drm_gem_shmem_vunmap_local - Unmap a virtual mapping fo a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Kernel virtual address where the SHMEM GEM object was mapped
• • This function cleans up a kernel virtual address mapping acquired by
• • drm_gem_shmem_vmap_local(). The mapping is only removed when the use count
• • drops to zero.
• • The function is called with the BO's reservation object locked.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local.
• • But it can also be called by drivers directly, in which case it will hide
• • the differences between dma-buf imported and natively allocated objects.
• */

+void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• dma_resv_assert_held(obj->resv);
• mutex_lock(&shmem->vmap_lock);
• drm_gem_shmem_vunmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);

+} +EXPORT_SYMBOL(drm_gem_shmem_vunmap_local);

struct drm_gem_shmem_object * drm_gem_shmem_create_with_handle(struct drm_file *file_priv, struct drm_device *dev, size_t size, diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index 434328d8a0d9..3f59bdf749aa 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -114,7 +114,9 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem); int drm_gem_shmem_pin(struct drm_gem_object *obj); void drm_gem_shmem_unpin(struct drm_gem_object *obj); int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map); +int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map); void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map); +void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map);

int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv);

-- 2.29.2

On Tue, Jan 12, 2021 at 02:11:24PM +0100, Thomas Zimmermann wrote:

Hi

Am 11.01.21 um 17:50 schrieb Daniel Vetter:

...

On Fri, Jan 08, 2021 at 10:43:31AM +0100, Thomas Zimmermann wrote:

...

Implementations of the vmap/vunmap GEM callbacks may perform pinning of the BO and may acquire the associated reservation object's lock. Callers that only require a mapping of the contained memory can thus interfere with other tasks that require exact pinning, such as scanout. This is less of an issue with private SHMEM buffers, but may happen with imported ones.

Therefore provide the new interfaces drm_gem_shmem_vmap_local() and drm_gem_shmem_vunmap_local(), which only perform the vmap/vunmap operations. Callers have to hold the reservation lock while the mapping persists.

This patch also connects GEM SHMEM helpers to GEM object functions with equivalent functionality.

v4:

• call dma_buf_{vmap,vunmap}_local() where necessary (Daniel)
• move driver changes into separate patches (Daniel)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

drivers/gpu/drm/drm_gem_shmem_helper.c | 90 +++++++++++++++++++++++--- include/drm/drm_gem_shmem_helper.h | 2 + 2 files changed, 84 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 9825c378dfa6..298832b2b43b 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -32,6 +32,8 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs = { .get_sg_table = drm_gem_shmem_get_sg_table, .vmap = drm_gem_shmem_vmap, .vunmap = drm_gem_shmem_vunmap,

• .vmap_local = drm_gem_shmem_vmap_local,
• .vunmap_local = drm_gem_shmem_vunmap_local, .mmap = drm_gem_shmem_mmap, };

@@ -261,7 +263,8 @@ void drm_gem_shmem_unpin(struct drm_gem_object *obj) } EXPORT_SYMBOL(drm_gem_shmem_unpin); -static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map) +static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map,

• 		     bool local)
  

This is a bit spaghetti and also has the problem that we're not changing shmem->vmap_use_count under different locks, depending upon which path we're taking.

I think the cleanest would be if we pull the if (import_attach) case out of the _locked() version completely, for all cases, and also outside of the shmem->vmap_lock. This means no caching of vmaps in the shmem layer anymore for imported buffers, but this is no longer a problem: We cache them in the exporters instead (I think at least, if not maybe need to fix that where it's expensive).

If we do that, what protects shmem->vaddr from concurrent access near line 281? would it be kept NULL then?

Also, we have some stats in debugfs (see drm_gem_shmem_print_info) which would be incorrect (or misleading at least).

We'd need to disable all that for pass-through vmap of imported objects.

Given all that, would it be possible to remove vmap_lock in favor of taking the resv lock in vmap/vunmap?

All possible (and imo long-term desirable), the trouble is in rolling it out. I've looked at rolling out dma_resv as the one and only lock for shmem helpers before, and gave up. Exynos is the worst (but not the only) offender: - it has it's own per-object lock - that per-object lock is taken most often before calling into various vfuncs, which means for a gradual transition the dma_resv lock would nest within that existing per-object lock (until we've completely replaced it) - but exynos also uses dma_resv already as an outermost lock in its command submission path

iow as soon as you add dma_resv_lock anywhere in shmem helpers, we've angered lockdep with a deadlock.

That means the only path I think is feasible is adding dma_resv lock to all drivers paths first, _outside_ of any existing driver specific per-object locks. Then remove the driver-specific object locks, and only then can we sprinkle dma_resv_assert_locked all over shmem helpers.

Ofc any driver without per-driver locks of their own could directly switch over to dma_resv lock, but until we've converted over all the drivers with their own locking shmem helpers would be stuck where they are right now.

I gave up :-/ But maybe if you only try to tackle vmap it might be feasible, since a lot fewer callers.

Cheers, Daniel

Best regards Thomas

...

Other option would be to unly pull it out for the _vmap_local case, but that's a bit ugly because no longer symmetrical in the various paths.

...

{ struct drm_gem_object *obj = &shmem->base; int ret = 0; @@ -272,7 +275,10 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct } if (obj->import_attach) {

• ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	ret = dma_buf_vmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

  if (!ret) { if (WARN_ON(map->is_iomem)) { ret = -EIO;

@@ -313,7 +319,7 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct return ret; } -/* +/**

• drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
• @shmem: shmem GEM object
• @map: Returns the kernel virtual address of the SHMEM GEM object's backing

@@ -339,15 +345,53 @@ int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map) ret = mutex_lock_interruptible(&shmem->vmap_lock); if (ret) return ret;

• ret = drm_gem_shmem_vmap_locked(shmem, map);

• ret = drm_gem_shmem_vmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock); return ret; } EXPORT_SYMBOL(drm_gem_shmem_vmap);

+/**

• • drm_gem_shmem_vmap_local - Create a virtual mapping for a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Returns the kernel virtual address of the SHMEM GEM object's backing

• •   store.
    

• • This function makes sure that a contiguous kernel virtual address mapping
• • exists for the buffer backing the shmem GEM object.
• • The function is called with the BO's reservation object locked. Callers must
• • hold the lock until after unmapping the buffer.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local. But
• • it can also be called by drivers directly, in which case it will hide the
• • differences between dma-buf imported and natively allocated objects.

So for the other callbacks I tried to make sure we have different entry points for this, since it's not really the same thing and because of the locking mess we have with dma_resv_lock vs various pre-existing local locking scheme, it's easy to get a mess.

I think the super clean version here would be to also export just the internal stuff for the ->v(un)map_local hooks, but that's maybe a bit too much boilerplate for no real gain. -Daniel

...

• • Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_local().
• • Returns:
• • 0 on success or a negative error code on failure.
• */

+int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• int ret;
• dma_resv_assert_held(obj->resv);
• ret = mutex_lock_interruptible(&shmem->vmap_lock);
• if (ret)

• return ret;
  

• ret = drm_gem_shmem_vmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);
• return ret;

+} +EXPORT_SYMBOL(drm_gem_shmem_vmap_local);

• static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,

• 			struct dma_buf_map *map)
  

• 			struct dma_buf_map *map, bool local)
  

  { struct drm_gem_object *obj = &shmem->base;

@@ -358,7 +402,10 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, return; if (obj->import_attach)

• dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	dma_buf_vunmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

  else vunmap(shmem->vaddr);

@@ -366,7 +413,7 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, drm_gem_shmem_put_pages(shmem); } -/* +/**

• drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
• @shmem: shmem GEM object
• @map: Kernel virtual address where the SHMEM GEM object was mapped

@@ -384,11 +431,38 @@ void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map) struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); mutex_lock(&shmem->vmap_lock);

• drm_gem_shmem_vunmap_locked(shmem, map);

• drm_gem_shmem_vunmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock); } EXPORT_SYMBOL(drm_gem_shmem_vunmap);

+/**

• • drm_gem_shmem_vunmap_local - Unmap a virtual mapping fo a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Kernel virtual address where the SHMEM GEM object was mapped
• • This function cleans up a kernel virtual address mapping acquired by
• • drm_gem_shmem_vmap_local(). The mapping is only removed when the use count
• • drops to zero.
• • The function is called with the BO's reservation object locked.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local.
• • But it can also be called by drivers directly, in which case it will hide
• • the differences between dma-buf imported and natively allocated objects.
• */

+void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• dma_resv_assert_held(obj->resv);
• mutex_lock(&shmem->vmap_lock);
• drm_gem_shmem_vunmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);

+} +EXPORT_SYMBOL(drm_gem_shmem_vunmap_local);

• struct drm_gem_shmem_object * drm_gem_shmem_create_with_handle(struct drm_file *file_priv, struct drm_device *dev, size_t size,

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index 434328d8a0d9..3f59bdf749aa 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -114,7 +114,9 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem); int drm_gem_shmem_pin(struct drm_gem_object *obj); void drm_gem_shmem_unpin(struct drm_gem_object *obj); int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map); +int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map); void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map); +void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map); int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv); -- 2.29.2

-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer

On Wed, Jan 27, 2021 at 01:08:05PM +0100, Thomas Zimmermann wrote:

Hi

Am 11.01.21 um 17:50 schrieb Daniel Vetter:

...

On Fri, Jan 08, 2021 at 10:43:31AM +0100, Thomas Zimmermann wrote:

...

Implementations of the vmap/vunmap GEM callbacks may perform pinning of the BO and may acquire the associated reservation object's lock. Callers that only require a mapping of the contained memory can thus interfere with other tasks that require exact pinning, such as scanout. This is less of an issue with private SHMEM buffers, but may happen with imported ones.

Therefore provide the new interfaces drm_gem_shmem_vmap_local() and drm_gem_shmem_vunmap_local(), which only perform the vmap/vunmap operations. Callers have to hold the reservation lock while the mapping persists.

This patch also connects GEM SHMEM helpers to GEM object functions with equivalent functionality.

v4:

• call dma_buf_{vmap,vunmap}_local() where necessary (Daniel)
• move driver changes into separate patches (Daniel)

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

drivers/gpu/drm/drm_gem_shmem_helper.c | 90 +++++++++++++++++++++++--- include/drm/drm_gem_shmem_helper.h | 2 + 2 files changed, 84 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 9825c378dfa6..298832b2b43b 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -32,6 +32,8 @@ static const struct drm_gem_object_funcs drm_gem_shmem_funcs = { .get_sg_table = drm_gem_shmem_get_sg_table, .vmap = drm_gem_shmem_vmap, .vunmap = drm_gem_shmem_vunmap,

• .vmap_local = drm_gem_shmem_vmap_local,
• .vunmap_local = drm_gem_shmem_vunmap_local, .mmap = drm_gem_shmem_mmap, };

@@ -261,7 +263,8 @@ void drm_gem_shmem_unpin(struct drm_gem_object *obj) } EXPORT_SYMBOL(drm_gem_shmem_unpin); -static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map) +static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct dma_buf_map *map,

• 		     bool local)
  

This is a bit spaghetti and also has the problem that we're not changing shmem->vmap_use_count under different locks, depending upon which path we're taking.

I think the cleanest would be if we pull the if (import_attach) case out of the _locked() version completely, for all cases, and also outside of the shmem->vmap_lock. This means no caching of vmaps in the shmem layer anymore for imported buffers, but this is no longer a problem: We cache them in the exporters instead (I think at least, if not maybe need to fix that where it's expensive).

There's no vmap refcounting in amdgpu AFAICT. So importing pages from there into an SHMEM object has the potential of breaking. IIRC same fro radeon and nouveau.

As long as the pinning is refcounted I think it should be fine, it's just that if you have multiple vmaps (e.g. 2 udl devices plugged in) we'll set up 2 vmaps. Which is a point pointless, but not really harmful. At least on 64bit where there's enough virtual address space.

So I'm somewhat reluctant to making this change. I guess I'll look elsewhere first to fix some of the locking issues (e.g., my recent ast cursor patches).

If this would break for amdgpu/radeon/nouveau then we already have a bug, since 2 udl devices can provoke this issue already as-is. So I don't think this should be a blocker. -Daniel

Best regards Thomas

...

Other option would be to unly pull it out for the _vmap_local case, but that's a bit ugly because no longer symmetrical in the various paths.

...

{ struct drm_gem_object *obj = &shmem->base; int ret = 0; @@ -272,7 +275,10 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct } if (obj->import_attach) {

• ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	ret = dma_buf_vmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	ret = dma_buf_vmap(obj->import_attach->dmabuf, map);
  

  if (!ret) { if (WARN_ON(map->is_iomem)) { ret = -EIO;

@@ -313,7 +319,7 @@ static int drm_gem_shmem_vmap_locked(struct drm_gem_shmem_object *shmem, struct return ret; } -/* +/**

• drm_gem_shmem_vmap - Create a virtual mapping for a shmem GEM object
• @shmem: shmem GEM object
• @map: Returns the kernel virtual address of the SHMEM GEM object's backing

@@ -339,15 +345,53 @@ int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map) ret = mutex_lock_interruptible(&shmem->vmap_lock); if (ret) return ret;

• ret = drm_gem_shmem_vmap_locked(shmem, map);

• ret = drm_gem_shmem_vmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock); return ret; } EXPORT_SYMBOL(drm_gem_shmem_vmap);

+/**

• • drm_gem_shmem_vmap_local - Create a virtual mapping for a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Returns the kernel virtual address of the SHMEM GEM object's backing

• •   store.
    

• • This function makes sure that a contiguous kernel virtual address mapping
• • exists for the buffer backing the shmem GEM object.
• • The function is called with the BO's reservation object locked. Callers must
• • hold the lock until after unmapping the buffer.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local. But
• • it can also be called by drivers directly, in which case it will hide the
• • differences between dma-buf imported and natively allocated objects.

So for the other callbacks I tried to make sure we have different entry points for this, since it's not really the same thing and because of the locking mess we have with dma_resv_lock vs various pre-existing local locking scheme, it's easy to get a mess.

I think the super clean version here would be to also export just the internal stuff for the ->v(un)map_local hooks, but that's maybe a bit too much boilerplate for no real gain. -Daniel

...

• • Acquired mappings should be cleaned up by calling drm_gem_shmem_vunmap_local().
• • Returns:
• • 0 on success or a negative error code on failure.
• */

+int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• int ret;
• dma_resv_assert_held(obj->resv);
• ret = mutex_lock_interruptible(&shmem->vmap_lock);
• if (ret)

• return ret;
  

• ret = drm_gem_shmem_vmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);
• return ret;

+} +EXPORT_SYMBOL(drm_gem_shmem_vmap_local);

• static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem,

• 			struct dma_buf_map *map)
  

• 			struct dma_buf_map *map, bool local)
  

  { struct drm_gem_object *obj = &shmem->base;

@@ -358,7 +402,10 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, return; if (obj->import_attach)

• dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

• if (local)
  

• 	dma_buf_vunmap_local(obj->import_attach->dmabuf, map);
  

• else
  

• 	dma_buf_vunmap(obj->import_attach->dmabuf, map);
  

  else vunmap(shmem->vaddr);

@@ -366,7 +413,7 @@ static void drm_gem_shmem_vunmap_locked(struct drm_gem_shmem_object *shmem, drm_gem_shmem_put_pages(shmem); } -/* +/**

• drm_gem_shmem_vunmap - Unmap a virtual mapping fo a shmem GEM object
• @shmem: shmem GEM object
• @map: Kernel virtual address where the SHMEM GEM object was mapped

@@ -384,11 +431,38 @@ void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map) struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); mutex_lock(&shmem->vmap_lock);

• drm_gem_shmem_vunmap_locked(shmem, map);

• drm_gem_shmem_vunmap_locked(shmem, map, false); mutex_unlock(&shmem->vmap_lock); } EXPORT_SYMBOL(drm_gem_shmem_vunmap);

+/**

• • drm_gem_shmem_vunmap_local - Unmap a virtual mapping fo a shmem GEM object
• • @shmem: shmem GEM object
• • @map: Kernel virtual address where the SHMEM GEM object was mapped
• • This function cleans up a kernel virtual address mapping acquired by
• • drm_gem_shmem_vmap_local(). The mapping is only removed when the use count
• • drops to zero.
• • The function is called with the BO's reservation object locked.
• • This function can be used to implement &drm_gem_object_funcs.vmap_local.
• • But it can also be called by drivers directly, in which case it will hide
• • the differences between dma-buf imported and natively allocated objects.
• */

+void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map) +{

• struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj);
• dma_resv_assert_held(obj->resv);
• mutex_lock(&shmem->vmap_lock);
• drm_gem_shmem_vunmap_locked(shmem, map, true);
• mutex_unlock(&shmem->vmap_lock);

+} +EXPORT_SYMBOL(drm_gem_shmem_vunmap_local);

• struct drm_gem_shmem_object * drm_gem_shmem_create_with_handle(struct drm_file *file_priv, struct drm_device *dev, size_t size,

diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index 434328d8a0d9..3f59bdf749aa 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -114,7 +114,9 @@ void drm_gem_shmem_put_pages(struct drm_gem_shmem_object *shmem); int drm_gem_shmem_pin(struct drm_gem_object *obj); void drm_gem_shmem_unpin(struct drm_gem_object *obj); int drm_gem_shmem_vmap(struct drm_gem_object *obj, struct dma_buf_map *map); +int drm_gem_shmem_vmap_local(struct drm_gem_object *obj, struct dma_buf_map *map); void drm_gem_shmem_vunmap(struct drm_gem_object *obj, struct dma_buf_map *map); +void drm_gem_shmem_vunmap_local(struct drm_gem_object *obj, struct dma_buf_map *map); int drm_gem_shmem_madvise(struct drm_gem_object *obj, int madv); -- 2.29.2

-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer

On Fri, Jan 08, 2021 at 10:43:32AM +0100, Thomas Zimmermann wrote:

Damage handling in mgag200 requires a short-term mapping of the source BO. Use drm_gem_shmem_vmap_local().

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

---

drivers/gpu/drm/mgag200/mgag200_mode.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c index 1dfc42170059..a33e28d4c5e9 100644 --- a/drivers/gpu/drm/mgag200/mgag200_mode.c +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c @@ -1552,22 +1552,32 @@ mgag200_handle_damage(struct mga_device *mdev, struct drm_framebuffer *fb, struct drm_rect *clip) { struct drm_device *dev = &mdev->base;

• struct drm_gem_object *obj = fb->obj[0]; struct dma_buf_map map; void *vmap; int ret;

• ret = drm_gem_shmem_vmap(fb->obj[0], &map);

• ret = dma_resv_lock(obj->resv, NULL); if (drm_WARN_ON(dev, ret))

• return; /* BUG: SHMEM BO should always be vmapped */
  

• return;
  

• ret = drm_gem_shmem_vmap_local(obj, &map);

• if (drm_WARN_ON(dev, ret))

• goto err_dma_resv_unlock; /* BUG: SHMEM BO should always be vmapped */
  

  vmap = map.vaddr; /* TODO: Use mapping abstraction properly */

  drm_fb_memcpy_dstclip(mdev->vram, vmap, fb, clip);

• drm_gem_shmem_vunmap(fb->obj[0], &map);

• drm_gem_shmem_vunmap_local(obj, &map);

• dma_resv_unlock(obj->resv);

  /* Always scanout image at VRAM offset 0 */ mgag200_set_startadd(mdev, (u32)0); mgag200_set_offset(mdev, fb);

• return;

+err_dma_resv_unlock:

• dma_resv_unlock(obj->resv);

}

static void

2.29.2

On Mon, Jan 11, 2021 at 06:00:42PM +0100, Daniel Vetter wrote:

On Fri, Jan 08, 2021 at 10:43:33AM +0100, Thomas Zimmermann wrote:

...

Damage handling in cirrus requires a short-term mapping of the source BO. Use drm_gem_shmem_vmap_local().

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

Hm more possible errors that we don't report to userspace ... Why don't we vmap/vunmap these in prepare/cleanup_fb? Generally we'd want a long-term vmap here to make sure this all works nicely.

Since it's nothing new, on this patch:

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

Ok, also strike this r-b here. This is called from that atomic commit paths, and we cannot call dma_resv_lock here. This should splat with lockdep enabled against the dma-fence annotations I've merged, I'm kinda surprised it doesn't? -Daniel

...

---

drivers/gpu/drm/tiny/cirrus.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/tiny/cirrus.c b/drivers/gpu/drm/tiny/cirrus.c index a043e602199e..21cd7056d45f 100644 --- a/drivers/gpu/drm/tiny/cirrus.c +++ b/drivers/gpu/drm/tiny/cirrus.c @@ -315,6 +315,7 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb, struct drm_rect *rect) { struct cirrus_device *cirrus = to_cirrus(fb->dev);

• struct drm_gem_object *obj = fb->obj[0]; struct dma_buf_map map; void *vmap; int idx, ret;

@@ -323,9 +324,12 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb, if (!drm_dev_enter(&cirrus->dev, &idx)) goto out;

• ret = drm_gem_shmem_vmap(fb->obj[0], &map);

• ret = dma_resv_lock(obj->resv, NULL); if (ret) goto out_dev_exit;

• ret = drm_gem_shmem_vmap_local(fb->obj[0], &map);

• if (ret)

• goto out_dma_resv_unlock;
  

  vmap = map.vaddr; /* TODO: Use mapping abstraction properly */

  if (cirrus->cpp == fb->format->cpp[0])

@@ -345,9 +349,11 @@ static int cirrus_fb_blit_rect(struct drm_framebuffer *fb, else WARN_ON_ONCE("cpp mismatch");

• drm_gem_shmem_vunmap(fb->obj[0], &map); ret = 0;

• drm_gem_shmem_vunmap_local(obj, &map);

+out_dma_resv_unlock:

• dma_resv_unlock(obj->resv);

out_dev_exit: drm_dev_exit(idx); out: -- 2.29.2

-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch

On Fri, Jan 08, 2021 at 10:43:34AM +0100, Thomas Zimmermann wrote:

Damage handling in gm12u320 requires a short-term mapping of the source BO. Use drm_gem_shmem_vmap_local().

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

drivers/gpu/drm/tiny/gm12u320.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/tiny/gm12u320.c b/drivers/gpu/drm/tiny/gm12u320.c index 33f65f4626e5..b0c6e350f2b3 100644 --- a/drivers/gpu/drm/tiny/gm12u320.c +++ b/drivers/gpu/drm/tiny/gm12u320.c @@ -265,11 +265,16 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320) y1 = gm12u320->fb_update.rect.y1; y2 = gm12u320->fb_update.rect.y2;

• ret = drm_gem_shmem_vmap(fb->obj[0], &map);

• ret = dma_resv_lock(fb->obj[0]->resv, NULL); if (ret) {

• GM12U320_ERR("failed to vmap fb: %d\n", ret);
  

• GM12U320_ERR("failed to reserve fb: %d\n", ret);
  

  goto put_fb; }

• ret = drm_gem_shmem_vmap_local(fb->obj[0], &map);

• if (ret) {

• GM12U320_ERR("failed to vmap fb: %d\n", ret);
  

• goto unlock_resv;
  

• } vaddr = map.vaddr; /* TODO: Use mapping abstraction properly */

  if (fb->obj[0]->import_attach) {

@@ -321,8 +326,11 @@ static void gm12u320_copy_fb_to_blocks(struct gm12u320_device *gm12u320) if (ret) GM12U320_ERR("dma_buf_end_cpu_access err: %d\n", ret); }

+unlock_resv:

• dma_resv_unlock(fb->obj[0]->resv);

Unlock before vunmap. -Daniel

vunmap:

• drm_gem_shmem_vunmap(fb->obj[0], &map);

• drm_gem_shmem_vunmap_local(fb->obj[0], &map);

put_fb: drm_framebuffer_put(fb); gm12u320->fb_update.fb = NULL; -- 2.29.2

Hi

Am 11.01.21 um 18:06 schrieb Daniel Vetter:

On Fri, Jan 08, 2021 at 10:43:38AM +0100, Thomas Zimmermann wrote:

...

Cursor updates in vboxvideo require a short-term mapping of the source BO. Use drm_gem_vram_vmap_local() and avoid the pinning operations.

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

All these drivers patches break the dma_resv_lock vs dma_fence_begin/end_signalling nesting rules, so this doesn't work.

Generally this is what the prepare/cleanup_fb hooks are for, that's where mappings (including vmaps) are meant to be set up, permanently.

I'm kinda not clear on why we need all these changes, I thought the locking problem is just in the fb helper paths, because it's outside of the atomic path and could conflict with an atomic update at the same time? So only that one should get the vmap_local treatment, everything else should keep the normal vmap treatment.

Kind of responding to all your comment on the driver changes:

These drivers only require short-term mappings, so using vmap_local would be the natural choice. For SHMEM helpers, it's mostly a cosmetic thing. For VRAM helpers, I was hoping to remove the vmap/vunmap helpers entirely. One cannot really map the BOs for the long-term, so not having the helpers at all would make sense.

But reading all your comments on the driver patches, I'd rather not update the drivers here but later convert them to use prepare_fb/cleanup_fb in the correct way.

Best regards Thomas

-Daniel

...

---

drivers/gpu/drm/vboxvideo/vbox_mode.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vboxvideo/vbox_mode.c b/drivers/gpu/drm/vboxvideo/vbox_mode.c index dbc0dd53c69e..215b37c78c10 100644 --- a/drivers/gpu/drm/vboxvideo/vbox_mode.c +++ b/drivers/gpu/drm/vboxvideo/vbox_mode.c @@ -381,7 +381,8 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane, container_of(plane->dev, struct vbox_private, ddev); struct vbox_crtc *vbox_crtc = to_vbox_crtc(plane->state->crtc); struct drm_framebuffer *fb = plane->state->fb;

• struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(fb->obj[0]);

• struct drm_gem_object *obj = fb->obj[0];
• struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(obj); u32 width = plane->state->crtc_w; u32 height = plane->state->crtc_h; size_t data_size, mask_size;

@@ -401,11 +402,12 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane,

vbox_crtc->cursor_enabled = true;

• ret = drm_gem_vram_vmap(gbo, &map);

• ret = dma_resv_lock(obj->resv, NULL);
• if (ret)

• return;
  

• ret = drm_gem_vram_vmap_local(gbo, &map); if (ret) {

• /*
  

•  * BUG: we should have pinned the BO in prepare_fb().
  

•  */
  

• dma_resv_unlock(obj->resv);
  

  mutex_unlock(&vbox->hw_mutex); DRM_WARN("Could not map cursor bo, skipping update\n"); return;

@@ -421,7 +423,8 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane, data_size = width * height * 4 + mask_size;

copy_cursor_image(src, vbox->cursor_data, width, height, mask_size);

• drm_gem_vram_vunmap(gbo, &map);

• drm_gem_vram_vunmap_local(gbo, &map);

• dma_resv_unlock(obj->resv);

  flags = VBOX_MOUSE_POINTER_VISIBLE | VBOX_MOUSE_POINTER_SHAPE | VBOX_MOUSE_POINTER_ALPHA;

-- 2.29.2

Hi

Am 12.01.21 um 10:17 schrieb Daniel Vetter:

On Tue, Jan 12, 2021 at 08:54:02AM +0100, Thomas Zimmermann wrote:

...

Hi

Am 11.01.21 um 18:06 schrieb Daniel Vetter:

...

On Fri, Jan 08, 2021 at 10:43:38AM +0100, Thomas Zimmermann wrote:

...

Cursor updates in vboxvideo require a short-term mapping of the source BO. Use drm_gem_vram_vmap_local() and avoid the pinning operations.

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

All these drivers patches break the dma_resv_lock vs dma_fence_begin/end_signalling nesting rules, so this doesn't work.

Generally this is what the prepare/cleanup_fb hooks are for, that's where mappings (including vmaps) are meant to be set up, permanently.

I'm kinda not clear on why we need all these changes, I thought the locking problem is just in the fb helper paths, because it's outside of the atomic path and could conflict with an atomic update at the same time? So only that one should get the vmap_local treatment, everything else should keep the normal vmap treatment.

Kind of responding to all your comment on the driver changes:

These drivers only require short-term mappings, so using vmap_local would be the natural choice. For SHMEM helpers, it's mostly a cosmetic thing. For VRAM helpers, I was hoping to remove the vmap/vunmap helpers entirely. One cannot really map the BOs for the long-term, so not having the helpers at all would make sense.

But reading all your comments on the driver patches, I'd rather not update the drivers here but later convert them to use prepare_fb/cleanup_fb in the correct way.

Ack from me on this plan. I think I got all the other patches with an r-b or ack?

The shmem patch needs an update from my side.

Best regards Thomas

-Daniel

...

Best regards Thomas

...

-Daniel

...

---

drivers/gpu/drm/vboxvideo/vbox_mode.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/vboxvideo/vbox_mode.c b/drivers/gpu/drm/vboxvideo/vbox_mode.c index dbc0dd53c69e..215b37c78c10 100644 --- a/drivers/gpu/drm/vboxvideo/vbox_mode.c +++ b/drivers/gpu/drm/vboxvideo/vbox_mode.c @@ -381,7 +381,8 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane, container_of(plane->dev, struct vbox_private, ddev); struct vbox_crtc *vbox_crtc = to_vbox_crtc(plane->state->crtc); struct drm_framebuffer *fb = plane->state->fb;

• struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(fb->obj[0]);

• struct drm_gem_object *obj = fb->obj[0];
• struct drm_gem_vram_object *gbo = drm_gem_vram_of_gem(obj); u32 width = plane->state->crtc_w; u32 height = plane->state->crtc_h; size_t data_size, mask_size;

@@ -401,11 +402,12 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane, vbox_crtc->cursor_enabled = true;

• ret = drm_gem_vram_vmap(gbo, &map);

• ret = dma_resv_lock(obj->resv, NULL);
• if (ret)

• return;
  

• ret = drm_gem_vram_vmap_local(gbo, &map); if (ret) {

• /*
  

•  * BUG: we should have pinned the BO in prepare_fb().
  

•  */
  

• dma_resv_unlock(obj->resv);
  mutex_unlock(&vbox->hw_mutex);
  DRM_WARN("Could not map cursor bo, skipping update\n");
  return;
  

@@ -421,7 +423,8 @@ static void vbox_cursor_atomic_update(struct drm_plane *plane, data_size = width * height * 4 + mask_size; copy_cursor_image(src, vbox->cursor_data, width, height, mask_size);

• drm_gem_vram_vunmap(gbo, &map);

• drm_gem_vram_vunmap_local(gbo, &map);
• dma_resv_unlock(obj->resv); flags = VBOX_MOUSE_POINTER_VISIBLE | VBOX_MOUSE_POINTER_SHAPE | VBOX_MOUSE_POINTER_ALPHA;

-- 2.29.2

-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Felix Imendörffer