On 2021-03-30 03:40 +0800, Xi Ruoyao wrote: > On 2021-03-29 21:36 +0200, Christian König wrote: > > Am 29.03.21 um 21:27 schrieb Xi Ruoyao: > > > Hi Christian, > > > > > > I don't think there is any constraint implemented to ensure `num_entries % > > > AMDGPU_GPU_PAGES_IN_CPU_PAGE == 0`. For example, in `amdgpu_vm_bo_map()`: > > > > > > /* validate the parameters */ > > > if (saddr & AMDGPU_GPU_PAGE_MASK || offset & AMDGPU_GPU_PAGE_MASK > > > > > > > > size == 0 || size & AMDGPU_GPU_PAGE_MASK) > > > return -EINVAL; > > > > > > /* snip */ > > > > > > saddr /= AMDGPU_GPU_PAGE_SIZE; > > > eaddr /= AMDGPU_GPU_PAGE_SIZE; > > > > > > /* snip */ > > > > > > mapping->start = saddr; > > > mapping->last = eaddr; > > > > > > > > > If we really want to ensure (mapping->last - mapping->start + 1) % > > > AMDGPU_GPU_PAGES_IN_CPU_PAGE == 0, then we should replace > > > "AMDGPU_GPU_PAGE_MASK" > > > in "validate the parameters" with "PAGE_MASK". It should be "~PAGE_MASK", "PAGE_MASK" has an opposite convention of "AMDGPU_GPU_PAGE_MASK" :(. > > Yeah, good point. > > > > > I tried it and it broke userspace: Xorg startup fails with EINVAL with > > > this > > > change. > > > > Well in theory it is possible that we always fill the GPUVM on a 4k > > basis while the native page size of the CPU is larger. Let me double > > check the code. On my platform, there are two issues both causing the VM corruption. One is fixed by agd5f/linux@fe001e7. Another is in Mesa from userspace: it uses `dev_info->gart_page_size` as the alignment, but the kernel AMDGPU driver expects it to use `dev_info->virtual_address_alignment`. If we can make the change to fill the GPUVM on a 4k basis, we can fix this issue and make virtual_address_alignment = 4K. Otherwise, we should fortify the parameter validation, changing "AMDGPU_GPU_PAGE_MASK" to "~PAGE_MASK". Then the userspace will just get an EINVAL, instead of a slient VM corruption. And someone should tell Mesa developers to fix the code in this case. -- Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx> School of Aerospace Science and Technology, Xidian University _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
