[PATCH] drm/amdkfd: fix a potential cu_mask memory leak
Yu, Lang
Lang.Yu at amd.com
Thu Sep 30 03:48:27 UTC 2021
>-----Original Message-----
>From: Kuehling, Felix <Felix.Kuehling at amd.com>
>Sent: Thursday, September 30, 2021 11:26 AM
>To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
><Ray.Huang at amd.com>
>Subject: Re: [PATCH] drm/amdkfd: fix a potential cu_mask memory leak
>
>On 2021-09-29 10:38 p.m., Yu, Lang wrote:
>>> -----Original Message-----
>>> From: Kuehling, Felix <Felix.Kuehling at amd.com>
>>> Sent: Thursday, September 30, 2021 10:28 AM
>>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
>>> <Ray.Huang at amd.com>
>>> Subject: Re: [PATCH] drm/amdkfd: fix a potential cu_mask memory leak
>>>
>>> On 2021-09-29 10:23 p.m., Yu, Lang wrote:
>>>>> -----Original Message-----
>>>>> From: Kuehling, Felix <Felix.Kuehling at amd.com>
>>>>> Sent: Thursday, September 30, 2021 9:47 AM
>>>>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>>>>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang, Ray
>>>>> <Ray.Huang at amd.com>
>>>>> Subject: Re: [PATCH] drm/amdkfd: fix a potential cu_mask memory
>>>>> leak
>>>>>
>>>>> On 2021-09-29 7:32 p.m., Yu, Lang wrote:
>>>>>> [AMD Official Use Only]
>>>>>>
>>>>>>
>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: Kuehling, Felix <Felix.Kuehling at amd.com>
>>>>>>> Sent: Wednesday, September 29, 2021 11:25 PM
>>>>>>> To: Yu, Lang <Lang.Yu at amd.com>; amd-gfx at lists.freedesktop.org
>>>>>>> Cc: Deucher, Alexander <Alexander.Deucher at amd.com>; Huang,
>Ray
>>>>>>> <Ray.Huang at amd.com>
>>>>>>> Subject: Re: [PATCH] drm/amdkfd: fix a potential cu_mask memory
>>>>>>> leak
>>>>>>>
>>>>>>> Am 2021-09-29 um 4:22 a.m. schrieb Lang Yu:
>>>>>>>> If user doesn't explicitly call kfd_ioctl_destroy_queue to
>>>>>>>> destroy all created queues, when the kfd process is destroyed,
>some queues'
>>>>>>>> cu_mask memory are not freed.
>>>>>>>>
>>>>>>>> To avoid forgetting to free them in some places, free them
>>>>>>>> immediately after use.
>>>>>>>>
>>>>>>>> Signed-off-by: Lang Yu <lang.yu at amd.com>
>>>>>>>> ---
>>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 8 ++++----
>>>>>>>> drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c |
>10
>>>>>>>> ++++------
>>>>>>>> 2 files changed, 8 insertions(+), 10 deletions(-)
>>>>>>>>
>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>>>>>> index 4de907f3e66a..5c0e6dcf692a 100644
>>>>>>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>>>>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c
>>>>>>>> @@ -451,8 +451,8 @@ static int kfd_ioctl_set_cu_mask(struct file
>>>>>>>> *filp, struct
>>>>>>> kfd_process *p,
>>>>>>>> retval = copy_from_user(properties.cu_mask, cu_mask_ptr,
>>>>>>> cu_mask_size);
>>>>>>>> if (retval) {
>>>>>>>> pr_debug("Could not copy CU mask from userspace");
>>>>>>>> - kfree(properties.cu_mask);
>>>>>>>> - return -EFAULT;
>>>>>>>> + retval = -EFAULT;
>>>>>>>> + goto out;
>>>>>>>> }
>>>>>>>>
>>>>>>>> mutex_lock(&p->mutex);
>>>>>>>> @@ -461,8 +461,8 @@ static int kfd_ioctl_set_cu_mask(struct file
>>>>>>>> *filp, struct kfd_process *p,
>>>>>>>>
>>>>>>>> mutex_unlock(&p->mutex);
>>>>>>>>
>>>>>>>> - if (retval)
>>>>>>>> - kfree(properties.cu_mask);
>>>>>>>> +out:
>>>>>>>> + kfree(properties.cu_mask);
>>>>>>>>
>>>>>>>> return retval;
>>>>>>>> }
>>>>>>>> diff --git
>>>>>>>> a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>>>>>>> b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>>>>>>> index 243dd1efcdbf..4c81d690f31a 100644
>>>>>>>> ---
>a/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>>>>>>> +++
>b/drivers/gpu/drm/amd/amdkfd/kfd_process_queue_manager.c
>>>>>>>> @@ -394,8 +394,6 @@ int pqm_destroy_queue(struct
>>>>>>> process_queue_manager *pqm, unsigned int qid)
>>>>>>>> pdd->qpd.num_gws = 0;
>>>>>>>> }
>>>>>>>>
>>>>>>>> - kfree(pqn->q->properties.cu_mask);
>>>>>>>> - pqn->q->properties.cu_mask = NULL;
>>>>>>>> uninit_queue(pqn->q);
>>>>>>>> }
>>>>>>>>
>>>>>>>> @@ -448,16 +446,16 @@ int pqm_set_cu_mask(struct
>>>>>>> process_queue_manager *pqm, unsigned int qid,
>>>>>>>> return -EFAULT;
>>>>>>>> }
>>>>>>>>
>>>>>>>> - /* Free the old CU mask memory if it is already allocated, then
>>>>>>>> - * allocate memory for the new CU mask.
>>>>>>>> - */
>>>>>>>> - kfree(pqn->q->properties.cu_mask);
>>>>>>>> + WARN_ON_ONCE(pqn->q->properties.cu_mask);
>>>>>>>>
>>>>>>>> pqn->q->properties.cu_mask_count = p->cu_mask_count;
>>>>>>>> pqn->q->properties.cu_mask = p->cu_mask;
>>>>>>>>
>>>>>>>> retval = pqn->q->device->dqm->ops.update_queue(pqn->q-
>>>> device->dqm,
>>>>>>>> pqn->q);
>>>>>>>> +
>>>>>>>> + pqn->q->properties.cu_mask = NULL;
>>>>>>>> +
>>>>>>> This won't work correctly. We need to save the cu_mask for later.
>>>>>>> Otherwise the next time dqm->ops.update_queue is called, for
>>>>>>> example in pqm_update_queue or pqm_set_gws, it will wipe out the
>>>>>>> CU mask in the
>>>>> MQD.
>>>>>> Let's just return when meeting a null cu_mask in update_cu_mask()
>>>>>> to avoid
>>>>> that.
>>>>>> Like following,
>>>>>>
>>>>>> static void update_cu_mask(struct mqd_manager *mm, void *mqd,
>>>>>> struct queue_properties *q)
>>>>>> {
>>>>>> struct v10_compute_mqd *m;
>>>>>> uint32_t se_mask[4] = {0}; /* 4 is the max # of SEs */
>>>>>>
>>>>>> if (!q-> cu_mask || q->cu_mask_count == 0)
>>>>>> return;
>>>>>> ......
>>>>>> }
>>>>>>
>>>>>> Is this fine with you? Thanks!
>>>>> I think that could work. I still don't like it. It leaves the CU
>>>>> mask in the q-
>>>>>> properties structure, but it's only ever used temporarily and
>>>>>> doesn't need to be
>>>>> persistent. I'd argue, in this case, the cu_mask shouldn't be in
>>>>> the
>>>>> q->properties structure at all, but should be passed as an optional
>>>>> parameter into the dqm-
>>>>>> ops.update_queue call.
>>>> The cu_mask is originally in q->properties structure. I didn't change that.
>>>> What I want to do is keeping the cu_mask memory allocation and
>>>> deallocation
>>> just in kfd_ioctl_set_cu_mask.
>>>> instead of everywhere.
>>> You're not changing where it is stored. But you're changing it from
>>> something persistent (while the queue exists) to something ephemeral
>>> (while the ioctl call is executing in the kernel). I think that would
>>> justify removing the persistent pointer
>> >from the q->properties structure.
>>
>> Mmm, actually it has been copied to mqd memory. It doesn't make too
>> much sense to keep it persistent.
>
>The current update_mqd implementations update the CU mask in the MQD
>from the one in the q->properties every time. So the persistent CU mask is
>currently needed.
The cu mask update actually happens when q->cu_mask_count != 0 in current update_cu_mask() implementation
(I think it should be q->cu_mask_count != 0 && q->cu_mask != NULL). So the fix may be enough.
You're right that this may not be necessary. But relying only
>on the persistent CU mask in the MQD would be a significant change in the
>way the CU mask is managed that would require updating all the ASIC-specific
>update_mqd implementations. Feel free to propose a patch that makes all
>those changes cleanly (including removing the cu_mask from the q-
>>properties structure).
>
>However, that goes beyond a simple memory leak fix. I think it would be
>worth it if it makes the code and data structures cleaner.
If you think it's better to propose a patch to make all those changes.
I will try to do it. I am just worry about there are many changes. Thanks!
Regards,
Lang
>>
>>>>> But I think a simpler fix would be to move the freeing of the CU mask
>>>>> into uninit_queue. That would catch all cases where a queue gets
>>>>> destroyed, including the process termination case.
>>>> Yes, it' better to free queue related resource in one function.
>>>> But we allocate it in kfd_ioctl_set_cu_mask and free it in
>pqm_set_cu_mask,
>>> uninit_queue and so on.
>>>
>>> My proposal here is to only free it in uninit_queue (when the queue is
>>> destroyed) or in pqm_set_cu_mask (when it is replaced by a different
>cu_mask).
>> Anyway, I still think it's strange and error-pone to allocate it in
>kfd_ioctl_set_cu_mask
>> and free it in uninit_queue and pqm_set_cu_mask.
>
>It would not change the code complexity from what we have now. You're
>just moving the free call from pqm_destroy_queue into uninit_queue. For
>a small bug fix, that's a pretty good deal.
>
>Regards,
> Felix
>
>
>>
>> Regards,
>> Lang
>>
>>> Regards,
>>> Felix
>>>
>>>
>>>> It seems strange and error-prone. Unless we allocate it in create queue.
>As you
>>> said, it is temporary.
>>>> It's not worth keeping it until queue is destroyed. Thanks.
>>>>
>>>> Regards,
>>>> Lang
>>>>
>>>>> Regards,
>>>>> Felix
>>>>>
>>>>>
>>>>>> Regards,
>>>>>> Lang
>>>>>>
>>>>>>> Regards,
>>>>>>> Felix
>>>>>>>
>>>>>>>
>>>>>>>> if (retval != 0)
>>>>>>>> return retval;
>>>>>>>>
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