Re: [PATCH 1/1] drm/amdgpu: add helper function for vm pasid

["Christian König" <ckoenig.leichtzumerken@gmail.com>]

Am 22.06.21 um 09:39 schrieb Das, Nirmoy:
>
> On 6/22/2021 9:03 AM, Christian König wrote:
>>
>>
>> Am 22.06.21 um 08:57 schrieb Nirmoy Das:
>>> Cleanup code related to vm pasid by adding helper functions.
>>>
>>> Signed-off-by: Nirmoy Das <nirmoy.das@amd.com>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 105 
>>> ++++++++++++-------------
>>>   1 file changed, 50 insertions(+), 55 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c 
>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> index 63975bda8e76..6e476b173cbb 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>> @@ -87,6 +87,46 @@ struct amdgpu_prt_cb {
>>>       struct dma_fence_cb cb;
>>>   };
>>>
>>> +static int amdgpu_vm_pasid_alloc(struct amdgpu_device *adev,
>>> +                 struct amdgpu_vm *vm,
>>> +                 unsigned int pasid,
>>> +                 unsigned int *vm_pasid)
>>> +{
>>> +    unsigned long flags;
>>> +    int r;
>>> +
>>> +    if (!pasid)
>>> +        return 0;
>>> +
>>> +    spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> +    r = idr_alloc(&adev->vm_manager.pasid_idr, vm, pasid, pasid + 1,
>>> +              GFP_ATOMIC);
>>> + spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> +    if (r < 0)
>>> +        return r;
>>> +    if (vm_pasid)
>>> +        *vm_pasid = pasid;
>>> +
>>
>> Ok the more I read from this patch the less it makes sense.
>>
>> We don't allocate the passid here, we just set it up in the idr.
>>
>> What we could do is to replace the idr with an xarray, that would 
>> certainly make more sense than this here.
>
>
> xarray looks great, with that we don't need pasid_lock either.

You still need the lock to protect against VM destruction while looking 
things up, but you could switch to RCU for this instead.

Christian.

>
>
> Thanks
>
> Nirmoy
>
>
>>
>> Christian.
>>
>>> +    return 0;
>>> +}
>>> +
>>> +static void amdgpu_vm_pasid_remove(struct amdgpu_device *adev,
>>> +                   unsigned int pasid,
>>> +                   unsigned int *vm_pasid)
>>> +{
>>> +    unsigned long flags;
>>> +
>>> +    if (!pasid)
>>> +        return;
>>> +
>>> +    spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> +    idr_remove(&adev->vm_manager.pasid_idr, pasid);
>>> + spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> +
>>> +    if (vm_pasid)
>>> +        *vm_pasid = 0;
>>> +}
>>> +
>>>   /*
>>>    * vm eviction_lock can be taken in MMU notifiers. Make sure no 
>>> reclaim-FS
>>>    * happens while holding this lock anywhere to prevent deadlocks when
>>> @@ -2940,18 +2980,8 @@ int amdgpu_vm_init(struct amdgpu_device 
>>> *adev, struct amdgpu_vm *vm, u32 pasid)
>>>
>>>       amdgpu_bo_unreserve(vm->root.bo);
>>>
>>> -    if (pasid) {
>>> -        unsigned long flags;
>>> -
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        r = idr_alloc(&adev->vm_manager.pasid_idr, vm, pasid, pasid 
>>> + 1,
>>> -                  GFP_ATOMIC);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -        if (r < 0)
>>> -            goto error_free_root;
>>> -
>>> -        vm->pasid = pasid;
>>> -    }
>>> +    if (amdgpu_vm_pasid_alloc(adev, vm, pasid, &vm->pasid))
>>> +        goto error_free_root;
>>>
>>>       INIT_KFIFO(vm->faults);
>>>
>>> @@ -3038,19 +3068,11 @@ int amdgpu_vm_make_compute(struct 
>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>       r = amdgpu_vm_check_clean_reserved(adev, vm);
>>>       if (r)
>>>           goto unreserve_bo;
>>> +    r = amdgpu_vm_pasid_alloc(adev, vm, pasid, NULL);
>>> +    if (r ==  -ENOSPC)
>>> +        goto unreserve_bo;
>>>
>>> -    if (pasid) {
>>> -        unsigned long flags;
>>> -
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        r = idr_alloc(&adev->vm_manager.pasid_idr, vm, pasid, pasid 
>>> + 1,
>>> -                  GFP_ATOMIC);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -
>>> -        if (r == -ENOSPC)
>>> -            goto unreserve_bo;
>>> -        r = 0;
>>> -    }
>>> +    r = 0;
>>>
>>>       /* Check if PD needs to be reinitialized and do it before
>>>        * changing any other state, in case it fails.
>>> @@ -3089,35 +3111,23 @@ int amdgpu_vm_make_compute(struct 
>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>       vm->is_compute_context = true;
>>>
>>>       if (vm->pasid) {
>>> -        unsigned long flags;
>>> -
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        idr_remove(&adev->vm_manager.pasid_idr, vm->pasid);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -
>>>           /* Free the original amdgpu allocated pasid
>>>            * Will be replaced with kfd allocated pasid
>>>            */
>>>           amdgpu_pasid_free(vm->pasid);
>>> -        vm->pasid = 0;
>>> +        amdgpu_vm_pasid_remove(adev, vm->pasid, &vm->pasid);
>>>       }
>>>
>>>       /* Free the shadow bo for compute VM */
>>> amdgpu_bo_unref(&to_amdgpu_bo_vm(vm->root.bo)->shadow);
>>> -
>>>       if (pasid)
>>>           vm->pasid = pasid;
>>>
>>>       goto unreserve_bo;
>>>
>>>   free_idr:
>>> -    if (pasid) {
>>> -        unsigned long flags;
>>> +    amdgpu_vm_pasid_remove(adev, pasid, NULL);
>>>
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        idr_remove(&adev->vm_manager.pasid_idr, pasid);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -    }
>>>   unreserve_bo:
>>>       amdgpu_bo_unreserve(vm->root.bo);
>>>       return r;
>>> @@ -3133,14 +3143,7 @@ int amdgpu_vm_make_compute(struct 
>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>    */
>>>   void amdgpu_vm_release_compute(struct amdgpu_device *adev, struct 
>>> amdgpu_vm *vm)
>>>   {
>>> -    if (vm->pasid) {
>>> -        unsigned long flags;
>>> -
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        idr_remove(&adev->vm_manager.pasid_idr, vm->pasid);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -    }
>>> -    vm->pasid = 0;
>>> +    amdgpu_vm_pasid_remove(adev, vm->pasid, &vm->pasid);
>>>       vm->is_compute_context = false;
>>>   }
>>>
>>> @@ -3164,15 +3167,7 @@ void amdgpu_vm_fini(struct amdgpu_device 
>>> *adev, struct amdgpu_vm *vm)
>>>
>>>       root = amdgpu_bo_ref(vm->root.bo);
>>>       amdgpu_bo_reserve(root, true);
>>> -    if (vm->pasid) {
>>> -        unsigned long flags;
>>> -
>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>> -        idr_remove(&adev->vm_manager.pasid_idr, vm->pasid);
>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>> -        vm->pasid = 0;
>>> -    }
>>> -
>>> +    amdgpu_vm_pasid_remove(adev, vm->pasid, &vm->pasid);
>>>       dma_fence_wait(vm->last_unlocked, false);
>>>       dma_fence_put(vm->last_unlocked);
>>>
>>> -- 
>>> 2.32.0
>>>
>>
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