Re: [PATCH v3 1/2] drm/amdkfd: Fix false positive queue buffer free warning

["Chen, Xiaogang" <xiaogang.chen@amd.com>]

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On 10/20/2025 9:30 AM, Philip Yang wrote:
> Only show warning message if process mm is still alive when queue
> buffer is freed.
>
> If kfd_lookup_process_by_mm return NULL, means the process is already
> exited and mm is gone, it is fine to free queue buffer.
>
> Fixes: b049504e211e ("drm/amdkfd: Validate user queue svm memory residency")
> Signed-off-by: Philip Yang<Philip.Yang@amd.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> index 4d4a47313f5b..d1b2f8525f80 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
> @@ -2487,7 +2487,9 @@ svm_range_unmap_from_cpu(struct mm_struct *mm, struct svm_range *prange,
>   	bool unmap_parent;
>   	uint32_t i;
>   
> -	if (atomic_read(&prange->queue_refcount)) {
> +	p = kfd_lookup_process_by_mm(mm);

p->mm is null, not p  because driver set p->mm to null. But still 
prange->queue_refcount is ref of queues from this prange. If app unmap 
this prange app should have destroyed the queues associated with this 
prange already. If not, it is not driver issue. I think driver should 
send this warning anyway to indicate there are queues not destroyed by 
app before app unmap the prange. It is an app race condition, not driver.

Regards

Xiaogang

> +
> +	if (p && atomic_read(&prange->queue_refcount)) {
>   		int r;
>   
>   		pr_warn("Freeing queue vital buffer 0x%lx, queue evicted\n",
> @@ -2497,7 +2499,6 @@ svm_range_unmap_from_cpu(struct mm_struct *mm, struct svm_range *prange,
>   			pr_debug("failed %d to quiesce KFD queues\n", r);
>   	}
>   
> -	p = kfd_lookup_process_by_mm(mm);
>   	if (!p)
>   		return;
>   	svms = &p->svms;

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