Re: [PATCH 1/1] drm/amdkfd: Add TLB flush after MES queue eviction/suspension

["Kuehling, Felix" <felix.kuehling@amd.com>]

On 2026-08-12 02:11, Priya Hosur wrote:
> MES (Micro Engine Scheduler) does not perform heavy-weight TLB invalidation
> after unmapping queues, unlike HWS which does this automatically. This causes
> a race condition where in-flight SDMA DMA descriptors can access memory that
> has been unmapped, leading to page faults and GPU queue hangs during SVM
> page migration.
>
> The issue manifests as KFDSVMRangeTest.MultiThreadMigrationTest/1 failures
> on gfx1151 (Ryzen AI MAX) with XNACK mode 1 enabled - the GPU compute queue
> hangs with packets submitted but never consumed.
>
> Add kfd_flush_tlb() with TLB_FLUSH_HEAVYWEIGHT in two MES code paths:
> 1. evict_process_queues_cpsch() - after MES removes queues
> 2. suspend_queues() - after MES suspends queues and mem_fence completes
>
> This ensures all in-flight memory accesses from unmapped queues are flushed
> before memory is freed or migrated.
>
> Testing on gfx1151 shows this reduces failure rate from 100% to approximately
> 7-10%. The residual failures require further investigation.
>
> Signed-off-by: Priya Hosur <Priya.Hosur@amd.com>
> ---
>   .../gpu/drm/amd/amdkfd/kfd_device_queue_manager.c   | 13 ++++++++++++-
>   1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> index a23384571193..5eb85290126e 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_device_queue_manager.c
> @@ -1450,6 +1450,14 @@ static int evict_process_queues_cpsch(struct device_queue_manager *dqm,
>   		dqm_evict_mqd_bo(dqm, q);
>   	}
>   
> +	/*
> +	 * Heavy-weight TLB flush after MES removes queues to ensure
> +	 * in-flight SDMA accesses complete before memory is freed/migrated.
> +	 * HWS does this automatically, MES does not.

I'm not sure why you call out SDMA specifically here. This affects 
in-flight memory accesses from compute jobs as well. Just remove "SDMA" 
from the comment. With that fixed, the patch is

Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>


> +	 */
> +	if (dqm->dev->kfd->shared_resources.enable_mes)
> +		kfd_flush_tlb(pdd, TLB_FLUSH_HEAVYWEIGHT);
> +
>   	if (!dqm->dev->kfd->shared_resources.enable_mes) {
>   		pdd->last_evict_timestamp = get_jiffies_64();
>   		retval = execute_queues_cpsch(dqm,
> @@ -3736,8 +3744,11 @@ int suspend_queues(struct kfd_process *p,
>   		if (!per_device_suspended) {
>   			dqm_unlock(dqm);
>   			mutex_unlock(&p->event_mutex);
> -			if (total_suspended)
> +			if (total_suspended) {
>   				amdgpu_amdkfd_debug_mem_fence(dqm->dev->adev);
> +				/* Heavy-weight TLB flush after MES suspends queues */
> +				kfd_flush_tlb(pdd, TLB_FLUSH_HEAVYWEIGHT);
> +			}
>   			continue;
>   		}
>