[PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Philip Yang]

Only show warning message if process mm is still alive when queue
buffer is freed to evcit the queues.

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);
+
+	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;
-- 
2.49.0

[PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Philip Yang]

In mmu notifier release callback, stop user queues to be safe because
the SVM memory is going to unmap from CPU.

Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
index 0341f570f3d1..e2a0ae0394b8 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
@@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct mmu_notifier *mn)
 
 static void kfd_process_notifier_release_internal(struct kfd_process *p)
 {
-	int i;
+	int i, r;
 
 	cancel_delayed_work_sync(&p->eviction_work);
 	cancel_delayed_work_sync(&p->restore_work);
 
+	WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
+	r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);
+	if (r)
+		pr_debug("failed %d to quiesce KFD queues\n", r);
+
 	for (i = 0; i < p->n_pdds; i++) {
 		struct kfd_process_device *pdd = p->pdds[i];
 
-- 
2.49.0

Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Chen, Xiaogang]

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On 10/15/2025 3:11 PM, Philip Yang wrote:
> In mmu notifier release callback, stop user queues to be safe because
> the SVM memory is going to unmap from CPU.
>
> Suggested-by: Felix Kuehling<felix.kuehling@amd.com>
> Signed-off-by: Philip Yang<Philip.Yang@amd.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index 0341f570f3d1..e2a0ae0394b8 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct mmu_notifier *mn)
>   
>   static void kfd_process_notifier_release_internal(struct kfd_process *p)
>   {
> -	int i;
> +	int i, r;
>   
>   	cancel_delayed_work_sync(&p->eviction_work);
>   	cancel_delayed_work_sync(&p->restore_work);
>   
> +	WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);

Use warning message or debug message? I saw this WARN are used several 
places. If the queues from kfd process p are still running when come 
here we need to stop them. It is not error. debug message is more 
suitable I think.

> +	r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);

The evict reason KFD_QUEUE_EVICTION_TRIGGER_SVM is not good here as it 
is general kfd process release. Maybe need another enum value.

Regards

Xiaogagn

> +	if (r)
> +		pr_debug("failed %d to quiesce KFD queues\n", r);
> +
>   	for (i = 0; i < p->n_pdds; i++) {
>   		struct kfd_process_device *pdd = p->pdds[i];
>   

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Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Philip Yang]

On 2025-10-15 16:40, Chen, Xiaogang wrote:
>
>
> On 10/15/2025 3:11 PM, Philip Yang wrote:
>> In mmu notifier release callback, stop user queues to be safe because
>> the SVM memory is going to unmap from CPU.
>>
>> Suggested-by: Felix Kuehling<felix.kuehling@amd.com>
>> Signed-off-by: Philip Yang<Philip.Yang@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> index 0341f570f3d1..e2a0ae0394b8 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> @@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct mmu_notifier *mn)
>>   
>>   static void kfd_process_notifier_release_internal(struct kfd_process *p)
>>   {
>> -	int i;
>> +	int i, r;
>>   
>>   	cancel_delayed_work_sync(&p->eviction_work);
>>   	cancel_delayed_work_sync(&p->restore_work);
>>   
>> +	WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
>
> Use warning message or debug message? I saw this WARN are used several 
> places. If the queues from kfd process p are still running when come 
> here we need to stop them. It is not error. debug message is more 
> suitable I think.
>
The module parameter debug_evictions can be set to true, use WARN to 
dump call back trace to help understand why queue is evicted, by default 
debug_evictions is false.
>> +	r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);
>
> The evict reason KFD_QUEUE_EVICTION_TRIGGER_SVM is not good here as it 
> is general kfd process release. Maybe need another enum value.
>
Define new profiling event requires rocprofiler API change, 
KFD_QUEUE_EVICTION_TRIGGER_SVM seems the closest event from mmu notifier.

Regards,

Philip

> Regards
>
> Xiaogagn
>
>> +	if (r)
>> +		pr_debug("failed %d to quiesce KFD queues\n", r);
>> +
>>   	for (i = 0; i < p->n_pdds; i++) {
>>   		struct kfd_process_device *pdd = p->pdds[i];
>>   

Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Chen, Xiaogang]

On 10/15/2025 4:33 PM, Philip Yang wrote:
>
> On 2025-10-15 16:40, Chen, Xiaogang wrote:
>>
>>
>> On 10/15/2025 3:11 PM, Philip Yang wrote:
>>> In mmu notifier release callback, stop user queues to be safe because
>>> the SVM memory is going to unmap from CPU.
>>>
>>> Suggested-by: Felix Kuehling<felix.kuehling@amd.com>
>>> Signed-off-by: Philip Yang<Philip.Yang@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c 
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>> index 0341f570f3d1..e2a0ae0394b8 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>> @@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct 
>>> mmu_notifier *mn)
>>>     static void kfd_process_notifier_release_internal(struct 
>>> kfd_process *p)
>>>   {
>>> -    int i;
>>> +    int i, r;
>>>         cancel_delayed_work_sync(&p->eviction_work);
>>>       cancel_delayed_work_sync(&p->restore_work);
>>>   +    WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
>>
>> Use warning message or debug message? I saw this WARN are used 
>> several places. If the queues from kfd process p are still running 
>> when come here we need to stop them. It is not error. debug message 
>> is more suitable I think.
>>
> The module parameter debug_evictions can be set to true, use WARN to 
> dump call back trace to help understand why queue is evicted, by 
> default debug_evictions is false.
I agree stopping  kfd process's queues during kfd process release. Just 
wonder if change WARN to debug message form. We can use dump_stack() to 
dump stack anyway, but it is not relevant to this patch.

>>> +    r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);
>>
>> The evict reason KFD_QUEUE_EVICTION_TRIGGER_SVM is not good here as 
>> it is general kfd process release. Maybe need another enum value.
>>
> Define new profiling event requires rocprofiler API change, 
> KFD_QUEUE_EVICTION_TRIGGER_SVM seems the closest event from mmu notifier.

That is awkward. We may add a emu value at end that rocprofile would not 
know for now.

Regards

Xiaogang


>
> Regards,
>
> Philip
>
>> Regards
>>
>> Xiaogagn
>>
>>> +    if (r)
>>> +        pr_debug("failed %d to quiesce KFD queues\n", r);
>>> +
>>>       for (i = 0; i < p->n_pdds; i++) {
>>>           struct kfd_process_device *pdd = p->pdds[i];

Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Felix Kuehling]

On 2025-10-16 10:46, Chen, Xiaogang wrote:
>
> On 10/15/2025 4:33 PM, Philip Yang wrote:
>>
>> On 2025-10-15 16:40, Chen, Xiaogang wrote:
>>>
>>>
>>> On 10/15/2025 3:11 PM, Philip Yang wrote:
>>>> In mmu notifier release callback, stop user queues to be safe because
>>>> the SVM memory is going to unmap from CPU.
>>>>
>>>> Suggested-by: Felix Kuehling<felix.kuehling@amd.com>
>>>> Signed-off-by: Philip Yang<Philip.Yang@amd.com>
>>>> ---
>>>>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>>>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c 
>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>>> index 0341f570f3d1..e2a0ae0394b8 100644
>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>>>> @@ -1221,11 +1221,16 @@ static void 
>>>> kfd_process_free_notifier(struct mmu_notifier *mn)
>>>>     static void kfd_process_notifier_release_internal(struct 
>>>> kfd_process *p)
>>>>   {
>>>> -    int i;
>>>> +    int i, r;
>>>>         cancel_delayed_work_sync(&p->eviction_work);
>>>>       cancel_delayed_work_sync(&p->restore_work);
>>>>   +    WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
>>>
>>> Use warning message or debug message? I saw this WARN are used 
>>> several places. If the queues from kfd process p are still running 
>>> when come here we need to stop them. It is not error. debug message 
>>> is more suitable I think.
>>>
>> The module parameter debug_evictions can be set to true, use WARN to 
>> dump call back trace to help understand why queue is evicted, by 
>> default debug_evictions is false.
> I agree stopping  kfd process's queues during kfd process release. 
> Just wonder if change WARN to debug message form. We can use 
> dump_stack() to dump stack anyway, but it is not relevant to this patch.
>
>>>> +    r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);
>>>
>>> The evict reason KFD_QUEUE_EVICTION_TRIGGER_SVM is not good here as 
>>> it is general kfd process release. Maybe need another enum value.
>>>
>> Define new profiling event requires rocprofiler API change, 
>> KFD_QUEUE_EVICTION_TRIGGER_SVM seems the closest event from mmu 
>> notifier.
>
> That is awkward. We may add a emu value at end that rocprofile would 
> not know for now.

roc-profile collects events in the running process context. This only 
happens on process termination. roc-profile will never see these events. 
So it really doesn't matter.

Regards,
   Felix



>
> Regards
>
> Xiaogang
>
>
>>
>> Regards,
>>
>> Philip
>>
>>> Regards
>>>
>>> Xiaogagn
>>>
>>>> +    if (r)
>>>> +        pr_debug("failed %d to quiesce KFD queues\n", r);
>>>> +
>>>>       for (i = 0; i < p->n_pdds; i++) {
>>>>           struct kfd_process_device *pdd = p->pdds[i];

Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Felix Kuehling]

On 2025-10-15 16:11, Philip Yang wrote:
> In mmu notifier release callback, stop user queues to be safe because
> the SVM memory is going to unmap from CPU.
>
> Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
> Signed-off-by: Philip Yang <Philip.Yang@amd.com>
> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index 0341f570f3d1..e2a0ae0394b8 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct mmu_notifier *mn)
>   
>   static void kfd_process_notifier_release_internal(struct kfd_process *p)
>   {
> -	int i;
> +	int i, r;
>   
>   	cancel_delayed_work_sync(&p->eviction_work);
>   	cancel_delayed_work_sync(&p->restore_work);
>   
> +	WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
> +	r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);

Is there a reason why we can't just call 
kfd_process_dequeue_from_all_devices here, and remove that call from 
kfd_process_wq_release? We don't need to call this an eviction. The 
queues get removed on process termination anyway. We're just doing it a 
bit earlier now.

Regards,
   Felix


> +	if (r)
> +		pr_debug("failed %d to quiesce KFD queues\n", r);
> +
>   	for (i = 0; i < p->n_pdds; i++) {
>   		struct kfd_process_device *pdd = p->pdds[i];
>   

Re: [PATCH v2 2/2] drm/amdkfd: Stop user queues when process mm released

[Philip Yang]

On 2025-10-17 18:43, Felix Kuehling wrote:
>
> On 2025-10-15 16:11, Philip Yang wrote:
>> In mmu notifier release callback, stop user queues to be safe because
>> the SVM memory is going to unmap from CPU.
>>
>> Suggested-by: Felix Kuehling <felix.kuehling@amd.com>
>> Signed-off-by: Philip Yang <Philip.Yang@amd.com>
>> ---
>>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c 
>> b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> index 0341f570f3d1..e2a0ae0394b8 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> @@ -1221,11 +1221,16 @@ static void kfd_process_free_notifier(struct 
>> mmu_notifier *mn)
>>     static void kfd_process_notifier_release_internal(struct 
>> kfd_process *p)
>>   {
>> -    int i;
>> +    int i, r;
>>         cancel_delayed_work_sync(&p->eviction_work);
>>       cancel_delayed_work_sync(&p->restore_work);
>>   +    WARN(debug_evictions, "Evicting pid %d", p->lead_thread->pid);
>> +    r = kfd_process_evict_queues(p, KFD_QUEUE_EVICTION_TRIGGER_SVM);
>
> Is there a reason why we can't just call 
> kfd_process_dequeue_from_all_devices here, and remove that call from 
> kfd_process_wq_release? We don't need to call this an eviction. The 
> queues get removed on process termination anyway. We're just doing it 
> a bit earlier now.

MMU release notifier callback don't hold mmap lock, it is safe to call 
kfd_process_dequeue_from_all_devices here, will send new version for review.

Regards,

Philip

>
> Regards,
>   Felix
>
>
>> +    if (r)
>> +        pr_debug("failed %d to quiesce KFD queues\n", r);
>> +
>>       for (i = 0; i < p->n_pdds; i++) {
>>           struct kfd_process_device *pdd = p->pdds[i];

Re: [PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Chen, Xiaogang]

On 10/15/2025 3:11 PM, Philip Yang wrote:
> Only show warning message if process mm is still alive when queue
> buffer is freed to evcit the queues.
>
> 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.

But another question is why a prange is still alive, its kfd process is 
gone?

When unmap a prange the queues that use it should have been stopped. If 
not, there is problem somewhere. This warning message need be sent no 
matter kfd process exists or not.

I think a real problem here is kfd process need be alive as long as any 
of its resource is still alive. In this case since prange is still alive 
its kfd process should not be released(p should not be null). If not we 
need wait all pranges from this process got released, then release this 
kfd process.

Regards

Xiaogang

>
> 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);
> +
> +	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;

Re: [PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Philip Yang]

On 2025-10-15 17:01, Chen, Xiaogang wrote:
>
> On 10/15/2025 3:11 PM, Philip Yang wrote:
>> Only show warning message if process mm is still alive when queue
>> buffer is freed to evcit the queues.
>>
>> 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.
>
> But another question is why a prange is still alive, its kfd process 
> is gone?
It is application process exited, kfd process structure still exist and 
available. The issue is race condition:

    do_exit
       exit_mmap
a.          mmu mm release notifier, schedule kfd release wq to destroy 
queue
              unmap_vmas
b.                mmu_notifier_range(.. MMU_NOTIFY_UNMAP...)

the step b is executed to unmap CWSR svm range, before step a kfd 
release wq destroy queue.


>
> When unmap a prange the queues that use it should have been stopped. 
> If not, there is problem somewhere. This warning message need be sent 
> no matter kfd process exists or not.
>
> I think a real problem here is kfd process need be alive as long as 
> any of its resource is still alive. In this case since prange is still 
> alive its kfd process should not be released(p should not be null). If 
> not we need wait all pranges from this process got released, then 
> release this kfd process.

kfd process structure is freed in kfd_process_wq_release after 
svm_range_list_fini.

Regards,

Philip

>
> Regards
>
> Xiaogang
>
>>
>> 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);
>> +
>> +    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;

Re: [PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Chen, Xiaogang]

On 10/15/2025 4:45 PM, Philip Yang wrote:
>
> On 2025-10-15 17:01, Chen, Xiaogang wrote:
>>
>> On 10/15/2025 3:11 PM, Philip Yang wrote:
>>> Only show warning message if process mm is still alive when queue
>>> buffer is freed to evcit the queues.
>>>
>>> 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.
>>
>> But another question is why a prange is still alive, its kfd process 
>> is gone?
> It is application process exited, kfd process structure still exist 
> and available. The issue is race condition:
>
>    do_exit
>       exit_mmap
> a.          mmu mm release notifier, schedule kfd release wq to 
> destroy queue
>              unmap_vmas
> b.                mmu_notifier_range(.. MMU_NOTIFY_UNMAP...)
>
> the step b is executed to unmap CWSR svm range, before step a kfd 
> release wq destroy queue.
>
>
>>
>> When unmap a prange the queues that use it should have been stopped. 
>> If not, there is problem somewhere. This warning message need be sent 
>> no matter kfd process exists or not.
>>
>> I think a real problem here is kfd process need be alive as long as 
>> any of its resource is still alive. In this case since prange is 
>> still alive its kfd process should not be released(p should not be 
>> null). If not we need wait all pranges from this process got 
>> released, then release this kfd process.
>
> kfd process structure is freed in kfd_process_wq_release after 
> svm_range_list_fini.

I wanted to say: delay remove kfd process p from kfd_processes_table 
until all resources of p got released. So when any p's resources is 
getting released p is available. That needs change kfd process release 
logic.


Regards

Xiaogang




>
> Regards,
>
> Philip
>
>>
>> Regards
>>
>> Xiaogang
>>
>>>
>>> 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);
>>> +
>>> +    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;

Re: [PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Philip Yang]

On 2025-10-15 18:46, Chen, Xiaogang wrote:
>
> On 10/15/2025 4:45 PM, Philip Yang wrote:
>>
>> On 2025-10-15 17:01, Chen, Xiaogang wrote:
>>>
>>> On 10/15/2025 3:11 PM, Philip Yang wrote:
>>>> Only show warning message if process mm is still alive when queue
>>>> buffer is freed to evcit the queues.
>>>>
>>>> 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.
>>>
>>> But another question is why a prange is still alive, its kfd process 
>>> is gone?
>> It is application process exited, kfd process structure still exist 
>> and available. The issue is race condition:
>>
>>    do_exit
>>       exit_mmap
>> a.          mmu mm release notifier, schedule kfd release wq to 
>> destroy queue
>>              unmap_vmas
>> b.                mmu_notifier_range(.. MMU_NOTIFY_UNMAP...)
>>
>> the step b is executed to unmap CWSR svm range, before step a kfd 
>> release wq destroy queue.
>>
>>
>>>
>>> When unmap a prange the queues that use it should have been stopped. 
>>> If not, there is problem somewhere. This warning message need be 
>>> sent no matter kfd process exists or not.
>>>
>>> I think a real problem here is kfd process need be alive as long as 
>>> any of its resource is still alive. In this case since prange is 
>>> still alive its kfd process should not be released(p should not be 
>>> null). If not we need wait all pranges from this process got 
>>> released, then release this kfd process.
>>
>> kfd process structure is freed in kfd_process_wq_release after 
>> svm_range_list_fini.
>
> I wanted to say: delay remove kfd process p from kfd_processes_table 
> until all resources of p got released. So when any p's resources is 
> getting released p is available. That needs change kfd process release 
> logic.

prange->queue_refcount will be 0 after queue is destroyed (not evicted), 
we should warn user space and evict queues if prange is freed with 
prange->queue_refcount not zero. This patch is to fix the race that 
generate false warning after process exited to free prange. I don't 
think that keep kfd process in kfd_processes_table after mmu release 
notifier will solve this race issue.

Regards,

Philip

>
>
> Regards
>
> Xiaogang
>
>
>
>
>>
>> Regards,
>>
>> Philip
>>
>>>
>>> Regards
>>>
>>> Xiaogang
>>>
>>>>
>>>> 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);
>>>> +
>>>> +    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;

Re: [PATCH v2 1/2] drm/amdkfd: Fix false positive queue buffer free warning

[Felix Kuehling]

On 2025-10-15 18:46, Chen, Xiaogang wrote:
>
> On 10/15/2025 4:45 PM, Philip Yang wrote:
>>
>> On 2025-10-15 17:01, Chen, Xiaogang wrote:
>>>
>>> On 10/15/2025 3:11 PM, Philip Yang wrote:
>>>> Only show warning message if process mm is still alive when queue
>>>> buffer is freed to evcit the queues.
>>>>
>>>> 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.
>>>
>>> But another question is why a prange is still alive, its kfd process 
>>> is gone?
>> It is application process exited, kfd process structure still exist 
>> and available. The issue is race condition:
>>
>>    do_exit
>>       exit_mmap
>> a.          mmu mm release notifier, schedule kfd release wq to 
>> destroy queue
>>              unmap_vmas
>> b.                mmu_notifier_range(.. MMU_NOTIFY_UNMAP...)
>>
>> the step b is executed to unmap CWSR svm range, before step a kfd 
>> release wq destroy queue.
>>
>>
>>>
>>> When unmap a prange the queues that use it should have been stopped. 
>>> If not, there is problem somewhere. This warning message need be 
>>> sent no matter kfd process exists or not.
>>>
>>> I think a real problem here is kfd process need be alive as long as 
>>> any of its resource is still alive. In this case since prange is 
>>> still alive its kfd process should not be released(p should not be 
>>> null). If not we need wait all pranges from this process got 
>>> released, then release this kfd process.
>>
>> kfd process structure is freed in kfd_process_wq_release after 
>> svm_range_list_fini.
>
> I wanted to say: delay remove kfd process p from kfd_processes_table 
> until all resources of p got released. So when any p's resources is 
> getting released p is available. That needs change kfd process release 
> logic.

That would complicate the cleanup a lot, because now other threads can 
still look up the kfd_process and use or modify it concurrently while 
the cleanup is happening. We remove the process from the 
kfd_processes_table first to ensure that it is safe to clean up all the 
process resources.

Regards,
   Felix


>
>
> Regards
>
> Xiaogang
>
>
>
>
>>
>> Regards,
>>
>> Philip
>>
>>>
>>> Regards
>>>
>>> Xiaogang
>>>
>>>>
>>>> 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);
>>>> +
>>>> +    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;