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accel/amdxdna: refuse to flush an imported BO

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SYNC_BO clflushes an imported BO's scatterlist. An importer may not do
that: the memory belongs to the exporter, and dma-buf gives the importer
no interface to ask for maintenance on it. Refuse the request instead.

is_import_bo() is (obj)->attach, which covers more than foreign buffers.
A userptr BO arrives through a ubuf, and on a carveout device every share
BO and the device heap arrive through a cbuf, so SYNC_BO answers
-EOPNOTSUPP for those too, including the AMDXDNA_BO_DEV path that flushes
through its heap.

Only the ubuf case gives up maintenance it was getting: on a 64 MiB
userptr BO a 4 KiB sync and a full sync both cost 659 us, this arm having
ignored the range. amdxdna_cbuf_map() fills in only the DMA address and
length, so drm_clflush_sg() already walks zero pages on carveout memory.
Userspace maintains these through the mapping it already holds, as XRT's
buffer::sync() does unless it is told to sync through the driver.

Fixes: dbc8fd7a03 ("accel/amdxdna: Add expandable device heap support")
Reported-by: Christian König <christian.koenig@amd.com>
Link: https://lore.kernel.org/dri-devel/a505f9e5-b416-43e9-934d-c5c29b8a70e9@amd.com/
Suggested-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Taimuraz Kaitmazov <taimuraz@kaitmazov.com>
Reviewed-by: Lizhi Hou <lizhi.hou@amd.com>
Signed-off-by: Lizhi Hou <lizhi.hou@amd.com>
Link: https://patch.msgid.link/20260819224458.257346-5-taimuraz@kaitmazov.com
This commit is contained in:
Taimuraz Kaitmazov 2026-08-20 01:44:57 +03:00 committed by Lizhi Hou
parent c2256c044a
commit 0ba8e0f900
1 changed files with 4 additions and 3 deletions
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7
drivers/accel/amdxdna/amdxdna_gem.c
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@ -1246,6 +1246,9 @@ static int amdxdna_flush_bo(struct amdxdna_gem_obj *abo, u64 offset, u64 size)
{
u64 end;
if (is_import_bo(abo))
return -EOPNOTSUPP;
if (offset >= abo->mem.size)
return -EINVAL;
@ -1256,9 +1259,7 @@ static int amdxdna_flush_bo(struct amdxdna_gem_obj *abo, u64 offset, u64 size)
if (!size)
return 0;
if (is_import_bo(abo))
drm_clflush_sg(abo->base.sgt);
else if (amdxdna_gem_vmap(abo))
if (amdxdna_gem_vmap(abo))
drm_clflush_virt_range(amdxdna_gem_vmap(abo) + offset, size);
else if (abo->base.pages)
drm_clflush_pages(abo->base.pages, abo->mem.size >> PAGE_SHIFT);