[PATCH] drm/amdkfd: fix a potential cu_mask memory leak
Yu, Lang
Lang.Yu at amd.com
Thu Sep 30 02:38:39 UTC 2021
>-----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.
>>
>>> 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.
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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