[PATCH] drm/amdgpu: fix KFDMemoryTest.PtraceAccessInvisibleVram fail on SRIOV

[Zhang, GuoQing (Sam)]

[AMD Official Use Only - AMD Internal Distribution Only]

Hi @Koenig, Christian<mailto:Christian.Koenig at amd.com> and @Kim, Jonathan<mailto:Jonathan.Kim at amd.com>,

Could you help review this patch?

Thanks
Sam

From: Samuel Zhang <guoqing.zhang at amd.com>
Date: Wednesday, August 7, 2024 at 16:36
To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Zhang, GuoQing (Sam) <GuoQing.Zhang at amd.com>
Subject: [PATCH] drm/amdgpu: fix KFDMemoryTest.PtraceAccessInvisibleVram fail on SRIOV
Ptrace access VRAM bo will first try sdma access in
amdgpu_ttm_access_memory_sdma(), if fails, it will fallback to mmio
access.

Since ptrace only access 8 bytes at a time and
amdgpu_ttm_access_memory_sdma() only allow PAGE_SIZE bytes access,
it returns fail.
On SRIOV, mmio access will also fail as MM_INDEX/MM_DATA register write
is blocked for security reasons.

The fix is just change len check in amdgpu_ttm_access_memory_sdma() so
that len in (0, PAGE_SIZE] are allowed. This will not fix the ptrace
test case on SRIOV, but also improve the access performance when the
access length is < PAGE_SIZE.
len > PAGE_SIZE case support is not needed as larger size will be break
into chunks of PAGE_SIZE len max in mem_rw().

Signed-off-by: Samuel Zhang <guoqing.zhang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 5daa05e23ddf..a6e90eada367 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1486,7 +1486,7 @@ static int amdgpu_ttm_access_memory_sdma(struct ttm_buffer_object *bo,
         unsigned int num_dw;
         int r, idx;

-       if (len != PAGE_SIZE)
+       if (len > PAGE_SIZE)
                 return -EINVAL;

         if (!adev->mman.sdma_access_ptr)
@@ -1514,7 +1514,7 @@ static int amdgpu_ttm_access_memory_sdma(struct ttm_buffer_object *bo,
                 swap(src_addr, dst_addr);

         amdgpu_emit_copy_buffer(adev, &job->ibs[0], src_addr, dst_addr,
-                               PAGE_SIZE, 0);
+                               len, 0);

         amdgpu_ring_pad_ib(adev->mman.buffer_funcs_ring, &job->ibs[0]);
         WARN_ON(job->ibs[0].length_dw > num_dw);
--
2.25.1
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