Am 12.08.24 um 08:59 schrieb Samuel Zhang: > 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 only 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.zh...@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;
We intentionally avoided that since the MM approach is usually preferable as long as you don't transmit large amounts of data. You could only add a check here for SRIOV. Regards, Christian. > > 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);
