FYI this patch got feedback at
https://lore.kernel.org/dri-devel/805acaca-3b91-438d-b842-25c055fd8...@amd.com/
Preferably the problem should be addressed on GEM/PRIME code instead of
dma-buf.
Best regards
Thomas
Am 14.08.25 um 09:34 schrieb Thomas Zimmermann:
Imported dma-buf objects need to be pinned while being vmap'ed into
kernel address space. This used to be done before while creating an
S/G table.
GEM-SHMEN can import dma-buf objects without creating the S/G table,
but the pin/unpin is now missing. Leads to page-mapping errors such
as the one shown below.
[ 102.101726] BUG: unable to handle page fault for address: ffffc90127000000
[...]
[ 102.157102] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl]
[...]
[ 102.243250] Call Trace:
[ 102.245695] <TASK>
[ 102.2477V95] ? validate_chain+0x24e/0x5e0
[ 102.251805] ? __lock_acquire+0x568/0xae0
[ 102.255807] udl_render_hline+0x165/0x341 [udl]
[ 102.260338] ? __pfx_udl_render_hline+0x10/0x10 [udl]
[ 102.265379] ? local_clock_noinstr+0xb/0x100
[ 102.269642] ? __lock_release.isra.0+0x16c/0x2e0
[ 102.274246] ? mark_held_locks+0x40/0x70
[ 102.278177] udl_primary_plane_helper_atomic_update+0x43e/0x680 [udl]
[ 102.284606] ? __pfx_udl_primary_plane_helper_atomic_update+0x10/0x10 [udl]
[ 102.291551] ? lockdep_hardirqs_on_prepare.part.0+0x92/0x170
[ 102.297208] ? lockdep_hardirqs_on+0x88/0x130
[ 102.301554] ? _raw_spin_unlock_irq+0x24/0x50
[ 102.305901] ? wait_for_completion_timeout+0x2bb/0x3a0
[ 102.311028] ? drm_atomic_helper_calc_timestamping_constants+0x141/0x200
[ 102.317714] ? drm_atomic_helper_commit_planes+0x3b6/0x1030
[ 102.323279] drm_atomic_helper_commit_planes+0x3b6/0x1030
[ 102.328664] drm_atomic_helper_commit_tail+0x41/0xb0
[ 102.333622] commit_tail+0x204/0x330
[...]
[ 102.529946] ---[ end trace 0000000000000000 ]---
[ 102.651980] RIP: 0010:udl_compress_hline16+0x219/0x940 [udl]
Support pin/unpin in drm_buf_map_attachment() without creating an S/G
table. Passing DMA_NONE for the DMA direction will only pin. Do the
inverse for unmap_attachment(). Modify GEM-SHMEM accordingly, so that
it pins the imported dma-buf.
Signed-off-by: Thomas Zimmermann <tzimmerm...@suse.de>
Fixes: 660cd44659a0 ("drm/shmem-helper: Import dmabuf without mapping its
sg_table")
Reported-by: Thomas Zimmermann <tzimmerm...@suse.de>
Closes:
https://lore.kernel.org/dri-devel/ba1bdfb8-dbf7-4372-bdcb-df7e0511c...@suse.de/
Cc: Shixiong Ou <oushixi...@kylinos.cn>
Cc: Thomas Zimmermann <tzimmerm...@suse.de>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Cc: Maxime Ripard <mrip...@kernel.org>
Cc: David Airlie <airl...@gmail.com>
Cc: Simona Vetter <sim...@ffwll.ch>
Cc: Sumit Semwal <sumit.sem...@linaro.org>
Cc: "Christian König" <christian.koe...@amd.com>
Cc: dri-devel@lists.freedesktop.org
Cc: linux-me...@vger.kernel.org
Cc: linaro-mm-...@lists.linaro.org
---
drivers/dma-buf/dma-buf.c | 16 +++++++++++++---
drivers/gpu/drm/drm_gem_shmem_helper.c | 11 ++++++++++-
drivers/gpu/drm/drm_prime.c | 2 ++
3 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 2bcf9ceca997..f1e1385ce630 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1086,7 +1086,8 @@ EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, "DMA_BUF");
* @direction: [in] direction of DMA transfer
*
* Returns sg_table containing the scatterlist to be returned; returns ERR_PTR
- * on error. May return -EINTR if it is interrupted by a signal.
+ * on error. May return -EINTR if it is interrupted by a signal. Returns NULL
+ * on success iff direction is DMA_NONE.
*
* On success, the DMA addresses and lengths in the returned scatterlist are
* PAGE_SIZE aligned.
@@ -1122,6 +1123,8 @@ struct sg_table *dma_buf_map_attachment(struct
dma_buf_attachment *attach,
if (ret)
return ERR_PTR(ret);
}
+ if (!valid_dma_direction(direction))
+ return NULL; /* only pin; don't map */
sg_table = attach->dmabuf->ops->map_dma_buf(attach, direction);
if (!sg_table)
@@ -1216,14 +1219,21 @@ void dma_buf_unmap_attachment(struct dma_buf_attachment
*attach,
{
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+ if (WARN_ON(!attach || !attach->dmabuf))
return;
dma_resv_assert_held(attach->dmabuf->resv);
+ if (!valid_dma_direction(direction))
+ goto unpin;
+
+ if (WARN_ON(!sg_table))
+ return;
+
mangle_sg_table(sg_table);
attach->dmabuf->ops->unmap_dma_buf(attach, sg_table, direction);
+unpin:
if (dma_buf_pin_on_map(attach))
attach->dmabuf->ops->unpin(attach);
}
@@ -1245,7 +1255,7 @@ void dma_buf_unmap_attachment_unlocked(struct
dma_buf_attachment *attach,
{
might_sleep();
- if (WARN_ON(!attach || !attach->dmabuf || !sg_table))
+ if (WARN_ON(!attach || !attach->dmabuf))
return;
dma_resv_lock(attach->dmabuf->resv, NULL);
diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c
b/drivers/gpu/drm/drm_gem_shmem_helper.c
index 5d1349c34afd..1b66501420d3 100644
--- a/drivers/gpu/drm/drm_gem_shmem_helper.c
+++ b/drivers/gpu/drm/drm_gem_shmem_helper.c
@@ -817,6 +817,7 @@ struct drm_gem_object
*drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
struct dma_buf
*dma_buf)
{
struct dma_buf_attachment *attach;
+ struct sg_table *sgt;
struct drm_gem_shmem_object *shmem;
struct drm_gem_object *obj;
size_t size;
@@ -838,12 +839,18 @@ struct drm_gem_object
*drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
get_dma_buf(dma_buf);
+ sgt = dma_buf_map_attachment_unlocked(attach, DMA_NONE);
+ if (IS_ERR(sgt)) {
+ ret = PTR_ERR(sgt);
+ goto fail_detach;
+ }
+
size = PAGE_ALIGN(attach->dmabuf->size);
shmem = __drm_gem_shmem_create(dev, size, true, NULL);
if (IS_ERR(shmem)) {
ret = PTR_ERR(shmem);
- goto fail_detach;
+ goto fail_unmap;
}
drm_dbg_prime(dev, "size = %zu\n", size);
@@ -853,6 +860,8 @@ struct drm_gem_object
*drm_gem_shmem_prime_import_no_map(struct drm_device *dev,
return &shmem->base;
+fail_unmap:
+ dma_buf_unmap_attachment_unlocked(attach, sgt, DMA_NONE);
fail_detach:
dma_buf_detach(dma_buf, attach);
dma_buf_put(dma_buf);
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 43a10b4af43a..b3b070868e3b 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -1109,6 +1109,8 @@ void drm_prime_gem_destroy(struct drm_gem_object *obj,
struct sg_table *sg)
attach = obj->import_attach;
if (sg)
dma_buf_unmap_attachment_unlocked(attach, sg,
DMA_BIDIRECTIONAL);
+ else
+ dma_buf_unmap_attachment_unlocked(attach, NULL, DMA_NONE);
dma_buf = attach->dmabuf;
dma_buf_detach(attach->dmabuf, attach);
/* remove the reference */
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)
