On Tue, Feb 17, 2026 at 11:38 AM Pierre-Eric Pelloux-Prayer
<[email protected]> wrote:
>
>
>
> Le 17/02/2026 à 17:20, Alex Deucher a écrit :
> > On Wed, Feb 11, 2026 at 6:07 AM Pierre-Eric Pelloux-Prayer
> > <[email protected]> wrote:
> >>
> >> Now that we have a worker thread, we can try to access the
> >> IBs of the job. The process is:
> >> * get the VM from the PASID
> >> * get the BO from its VA and the VM
> >> * map the BO for CPU access
> >> * copy everything, then add it to the dump
> >> Each step can fail so we have to be cautious.
> >> These operations can be slow so when amdgpu_devcoredump_format
> >> is called only to determine the size of the buffer we skip all
> >> of them and assume they will succeed.
> >>
> >> Signed-off-by: Pierre-Eric Pelloux-Prayer
> >> <[email protected]>
> >> ---
> >> .../gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c | 84 ++++++++++++++++++-
> >> 1 file changed, 83 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
> >> b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
> >> index d0af8a294abf..d576518c212d 100644
> >> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
> >> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dev_coredump.c
> >> @@ -200,12 +200,20 @@ static void amdgpu_devcoredump_fw_info(struct
> >> amdgpu_device *adev,
> >> static ssize_t
> >> amdgpu_devcoredump_format(char *buffer, size_t count, struct
> >> amdgpu_coredump_info *coredump)
> >> {
> >> + struct amdgpu_device *adev = coredump->adev;
> >> struct drm_printer p;
> >> struct drm_print_iterator iter;
> >> struct amdgpu_vm_fault_info *fault_info;
> >> + struct amdgpu_bo_va_mapping *mapping;
> >> struct amdgpu_ip_block *ip_block;
> >> + struct amdgpu_res_cursor cursor;
> >> + struct amdgpu_bo *abo, *root;
> >> + uint64_t va_start, offset;
> >> struct amdgpu_ring *ring;
> >> - int ver, i, j;
> >> + struct amdgpu_vm *vm;
> >> + u32 *ib_content;
> >> + uint8_t *kptr;
> >> + int ver, i, j, r;
> >> u32 ring_idx, off;
> >>
> >> iter.data = buffer;
> >> @@ -323,6 +331,80 @@ amdgpu_devcoredump_format(char *buffer, size_t count,
> >> struct amdgpu_coredump_inf
> >> else if (coredump->reset_vram_lost)
> >> drm_printf(&p, "VRAM is lost due to GPU reset!\n");
> >>
> >> + if (coredump->num_ibs) {
> >> + if (buffer)
> >> + vm = amdgpu_vm_lock_by_pasid(adev, &root,
> >> coredump->pasid);
> >> + else
> >> + vm = NULL;
> >
> > Is there any point in doing the loop if the vm is NULL?
>
> Yes : when doing the first pass to size the final buffer I skip the
> buffers mapping + read operations that might be slow and instead just
> account for the outputting of ib_size_dw dwords.
But if you don't map the buffer, you'll just be dumping the random
content from ib_content[].
>
> >
> >> +
> >> + for (int i = 0; i < coredump->num_ibs && (!buffer || vm);
> >> i++) {
> >> + ib_content =
> >> kvmalloc_array(coredump->ibs[i].ib_size_dw, 4,
> >> + GFP_KERNEL);
> >
> > Shouldn't this be GFP_NOWAIT?
>
> This is executed by a worker so GFP_KERNEL should be ok?
Oh, right. Yeah, should be ok.
Alex
>
> Pierre-Eric
>
> >
> > Alex
> >
> >> + if (!ib_content)
> >> + continue;
> >> +
> >> + if (!vm)
> >> + goto output_ib_content;
> >> +
> >> + va_start = coredump->ibs[i].gpu_addr &
> >> AMDGPU_GMC_HOLE_MASK;
> >> + mapping = amdgpu_vm_bo_lookup_mapping(vm, va_start
> >> / AMDGPU_GPU_PAGE_SIZE);
> >> + if (!mapping)
> >> + goto free_ib_content;
> >> +
> >> + offset = va_start - (mapping->start *
> >> AMDGPU_GPU_PAGE_SIZE);
> >> + abo = amdgpu_bo_ref(mapping->bo_va->base.bo);
> >> + r = amdgpu_bo_reserve(abo, false);
> >> + if (r)
> >> + goto free_ib_content;
> >> +
> >> + if (abo->flags & AMDGPU_GEM_CREATE_NO_CPU_ACCESS) {
> >> + off = 0;
> >> +
> >> + if (abo->tbo.resource->mem_type !=
> >> TTM_PL_VRAM)
> >> + goto unreserve_abo;
> >> +
> >> + amdgpu_res_first(abo->tbo.resource, offset,
> >> +
> >> coredump->ibs[i].ib_size_dw * 4,
> >> + &cursor);
> >> + while (cursor.remaining) {
> >> + amdgpu_device_mm_access(adev,
> >> cursor.start / 4,
> >> +
> >> &ib_content[off], cursor.size / 4,
> >> + false);
> >> + off += cursor.size;
> >> + amdgpu_res_next(&cursor,
> >> cursor.size);
> >> + }
> >> + } else {
> >> + r = ttm_bo_kmap(&abo->tbo, 0,
> >> + PFN_UP(abo->tbo.base.size),
> >> + &abo->kmap);
> >> + if (r)
> >> + goto unreserve_abo;
> >> +
> >> + kptr = amdgpu_bo_kptr(abo);
> >> + kptr += offset;
> >> + memcpy(ib_content, kptr,
> >> + coredump->ibs[i].ib_size_dw * 4);
> >> +
> >> + amdgpu_bo_kunmap(abo);
> >> + }
> >> +
> >> +output_ib_content:
> >> + drm_printf(&p, "\nIB #%d 0x%llx %d dw\n",
> >> + i, coredump->ibs[i].gpu_addr,
> >> coredump->ibs[i].ib_size_dw);
> >> + for (int j = 0; j < coredump->ibs[i].ib_size_dw;
> >> j++)
> >> + drm_printf(&p, "0x%08x\n", ib_content[j]);
> >> +unreserve_abo:
> >> + if (vm)
> >> + amdgpu_bo_unreserve(abo);
> >> +free_ib_content:
> >> + kfree(ib_content);
> >> + }
> >> + if (vm) {
> >> + amdgpu_bo_unreserve(root);
> >> + amdgpu_bo_unref(&root);
> >> + }
> >> + }
> >> +
> >> return count - iter.remain;
> >> }
> >>
> >> --
> >> 2.43.0
> >>
