On 2026-10-16 11:32, William Palacek wrote:
When a GPU reset takes the reset domain, KFD eviction cannot unmap
user queues: execute_queues_cpsch() fails its trylock with -EIO, so
the queues keep running until the ASIC is reset. The TLB flush is also
skipped while the reset is in progress. If the process unmaps and frees
a BO in that window, its pages are released while a queue can still
access them through stale translations.
On MI300X, munmap() then crashes in free_swap_cache() on a small bogus
page pointer in its mmu_gather batch page:
BUG: unable to handle page fault for address: 0000000000002900
RIP: 0010:free_swap_cache+0x5/0xb0
Call Trace:
free_pages_and_swap_cache+0x3a/0x60
tlb_batch_pages_flush+0x43/0x80
tlb_flush_mmu+0x3d/0x110
zap_pte_range+0x80d/0xcd0
...
do_vmi_align_munmap+0x3e8/0x5b0
do_vmi_munmap+0xdf/0x190
__vm_munmap+0xad/0x180
__x64_sys_munmap+0x1b/0x30
In a traced crash the bogus pointer was the read pointer value of an SDMA
queue the process had just destroyed, at the read pointer's page offset:
the queue's writeback landed in its freed rptr page after the page was
reused as the batch page.
commit f0b4440cdc18 ("drm/amdkfd: Fix mode1 reset crash issue") fixed
this race on process exit by waiting for the reset to complete before
freeing the process's BOs. Free through the ioctl has the same race.
Wait for the reset there too, using the same helper.
On GPU reset, kgd2kfd_pre_reset() sends a reset event to all processes
and ROCr then aborts the process. This is unfortunately racy: the
process can still be calling ioctls into KFD while the GPU reset is in
progress. The expectation is that the process stops issuing ioctls and
exits, after which kfd_process_wq_release() cleans up the remaining
system/VRAM memory, queues and so on.
Waiting for the GPU reset to complete inside the ioctl is not an option.
Once the thread blocks in the kernel on something like
flush_workqueue(), the wait is uninterruptible, so the pending
abort/exit cannot be delivered and the thread sits in D state until the
reset finishes. That defeats the whole point of aborting the process.
kgd2kfd_suspend_process() in the pre-reset path also sets the kfd_locked
flag, which is used to prevent a new KFD process from opening the KFD
node while a GPU reset is in progress.
So I think we could check kfd_locked and return -EBUSY from the KFD
ioctls. The application retries, eventually gets aborted, and the KFD
cleanup worker frees the resources once the GPU reset has completed.
Regards,
Philip
Fixes: 9c33e5fd4fb6 ("drm/amdgpu: fix locking scope when flushing tlb")
Signed-off-by: William Palacek<[email protected]>
---
Christian, Felix suggested asking you about a lower-level fix. In the
traces, the TLB flushes during the reset returned right away without
flushing, because amdgpu_gmc_flush_gpu_tlb_pasid_xccs() returns 0 when
it can't take the reset domain lock. So callers free memory the queue
can still access until the ASIC reset. The SVM munmap path goes through
the same flush. Felix thought a more general solution may be in
amdgpu_object.c or amdgpu_ttm.c. amdgpu_bo_release_notify() already adds
the wipe-on-release fence so TTM delays freeing the BO. Could a fence
that signals when the reset completes hold the pages the same way, or is
there a better place?
v5: new approach, replaces "drm/amdkfd: discard interrupts during a GPU
reset" (v4) and "drm/amdgpu: preempt KFD queues before taking the
reset domain lock" (v1-v3)
- v4 did not address the munmap Oops (Felix). Fix the cause instead:
BOs freed during a reset while user queues still access them
- Reuse kfd_process_wait_gpu_reset_complete() from commit
f0b4440cdc18 in the free-memory ioctl; no queue unmap, nothing sent
to the GPU during the reset (Christian)
- Drop the interrupt discard from v4
drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 3 +++
drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 1 +
drivers/gpu/drm/amd/amdkfd/kfd_process.c | 2 +-
3 files changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
index b3ebbee76088..0953d823c345 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
@@ -1305,6 +1305,9 @@ static int kfd_ioctl_free_memory_of_gpu(struct file
*filep,
goto err_unlock;
}
+ /* Queues a reset could not stop may still access the buffer */
+ kfd_process_wait_gpu_reset_complete(p);
+
ret = amdgpu_amdkfd_gpuvm_free_memory_of_gpu(pdd->dev->adev,
(struct kgd_mem *)mem, pdd->drm_priv, &size);
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
index 7a365fca68e4..25f57dd59bfd 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
@@ -1126,6 +1126,7 @@ void kfd_unref_process(struct kfd_process *p);
int kfd_process_evict_queues(struct kfd_process *p, uint32_t trigger);
int kfd_process_restore_queues(struct kfd_process *p);
void kfd_suspend_all_processes(void);
+void kfd_process_wait_gpu_reset_complete(struct kfd_process *p);
int kfd_resume_all_processes(void);
struct kfd_process_device *kfd_process_device_data_by_id(struct kfd_process *process,
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index e742ef206abd..7750741444ba 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1291,7 +1291,7 @@ static void kfd_process_remove_sysfs(struct kfd_process
*p)
/*
* If any GPU is ongoing reset, wait for reset complete.
*/
-static void kfd_process_wait_gpu_reset_complete(struct kfd_process *p)
+void kfd_process_wait_gpu_reset_complete(struct kfd_process *p)
{
int i;
