[PATCH 2/2] drm/amdgpu: use xarray for storing pasid in vm
Das, Nirmoy
nirmoy.das at amd.com
Wed Jun 23 15:24:08 UTC 2021
On 6/23/2021 5:02 PM, Christian König wrote:
>
>
> Am 23.06.21 um 16:54 schrieb Das, Nirmoy:
>>
>> On 6/23/2021 3:40 PM, Christian König wrote:
>>>
>>>
>>> Am 23.06.21 um 15:11 schrieb Das, Nirmoy:
>>>>
>>>> On 6/23/2021 2:50 PM, Christian König wrote:
>>>>>
>>>>>
>>>>> Am 23.06.21 um 14:25 schrieb Nirmoy Das:
>>>>>> Replace idr with xarray as we actually need hash functionality.
>>>>>> Cleanup code related to vm pasid by adding helper function.
>>>>>>
>>>>>> Signed-off-by: Nirmoy Das <nirmoy.das at amd.com>
>>>>>> ---
>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 134
>>>>>> +++++++++++--------------
>>>>>> drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h | 3 +-
>>>>>> 2 files changed, 60 insertions(+), 77 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>>> index be841d62a1d4..e047e56a4be2 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>>>>>> @@ -87,6 +87,39 @@ struct amdgpu_prt_cb {
>>>>>> struct dma_fence_cb cb;
>>>>>> };
>>>>>> +static int amdgpu_vm_set_pasid(struct amdgpu_device *adev,
>>>>>> + struct amdgpu_vm *vm,
>>>>>> + unsigned long pasid)
>>>>>
>>>>> Some kerneldoc please describing why we have that function.
>>>>
>>>>
>>>> Alright.
>>>>
>>>>
>>>>>
>>>>>> +{
>>>>>> + unsigned long flags;
>>>>>> + int r;
>>>>>> +
>>>>>> + if (pasid) {
>>>>>
>>>>> You should probably reorder the code so that the old pasid is
>>>>> first removed and then eventually the new one added.
>>>>>
>>>>>> + xa_lock_irqsave(&adev->vm_manager.pasids, flags);
>>>>>> + r = xa_err(__xa_store(&adev->vm_manager.pasids, pasid, vm,
>>>>>> + GFP_ATOMIC));
>>>>>> + xa_unlock_irqrestore(&adev->vm_manager.pasids, flags);
>>>>>
>>>>> As far as I can see this can just use xa_store() which also drops
>>>>> the need for GFP_ATOMIC here.
>>>>
>>>>
>>>> Do we need to have this irqsave/restore to keep passids safe for
>>>> amdgpu_vm_handle_fault() ?
>>>
>>> No, we need the VM safe not the pasid.
>>
>>
>> Would spin_lock_irq be enough to keep the VM safe then I can use
>> xa_store_irq() and remove some extra locking code?
>
> Yes, when when amdgpu_vm_set_pasid() is called we can be 100% sure
> that the VM won't be freed inside the function or otherwise I really
> question the saneness of the code.
>
>>>
>>>> xa_store() takes the spinlock without irq flags so I wanted to keep
>>>> old behavior.
>>>
>>> Yeah, that's indeed problematic. You need to keep that straight or
>>> lockdep will complain.
>>>
>>> IIRC there is also a function to reserve an entry before you take
>>> the lock. Maybe use that one.
>>
>>
>> xa_reserve() also takes a spin lock so I think this won't work either
>> with gfp_kernel flag.
>
> No, I just double checked. You can use xa_store_irq() with GFP_KERNEL.
>
> The implementation makes sure to not allocate while holding the lock.
>
>>
>>
>>>
>>>>
>>>>
>>>>>
>>>>>> + if (r < 0)
>>>>>> + return r;
>>>>>> + } else {
>>>>>> + unsigned long index;
>>>>>> + struct amdgpu_vm *res;
>>>>>> +
>>>>>> + xa_lock_irqsave(&adev->vm_manager.pasids, flags);
>>>>>> + xa_for_each(&adev->vm_manager.pasids, index, res) {
>>>>>> + if (res == vm) {
>>>>>> + __xa_erase(&adev->vm_manager.pasids, index);
>>>>>> + break;
>>>>>> + }
>>>>>> + }
>>>>>> + xa_unlock_irqrestore(&adev->vm_manager.pasids, flags);
>>>>>
>>>>> That is really ugly, why is that necessary?
>>>>
>>>> Do you mean the lock around xa_for_each() ? I think I can just used
>>>> lock around __xa_erase() or just xa_erase() if just simple spinlock
>>>> without flags is enough.
>>>
>>> I mean why you use xa_for_each() here?
>>
>>
>> amdgpu_vm_set_pasid() removes pasid:vm entry when pasid 0 is passed.
>> I need xa_for_each() to find the index of that vm pointer
>>
>> so that I can pass that to __xa_erase(). I couldn't find an API which
>> removes an entry by value.
>
> Ok sounds like you don't understand what semantics I suggest. Let me
> try once more:
>
> if (vm->pasid == pasid)
> return 0;
>
> if (vm->pasid)
> xa_erase_irq(..., vm->pasid);
>
> if (pasid)
> xa_store_irq(..., pasid, vm);
>
> vm->pasid = pasid;
>
> You of course need to add error handling and everything, but in
> general that should do it.
I guess I was over thinking. This looks much straight forward than what
I was thinking.
Thanks,
Nirmoy
>
> Thanks,
> Christian.
>
>>
>>
>> Regards,
>>
>> Nirmoy
>>
>>>
>>> Just __xa_erase should be enough.
>>>
>>> Christian.
>>>
>>>>
>>>>
>>>> Regards,
>>>>
>>>> Nirmoy
>>>>
>>>>
>>>>>
>>>>> Christian
>>>>>
>>>>>> + }
>>>>>> +
>>>>>> + vm->pasid = pasid;
>>>>>> +
>>>>>> + return 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 +2973,9 @@ 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;
>>>>>> - }
>>>>>> + r = amdgpu_vm_set_pasid(adev, vm, pasid);
>>>>>> + if (r)
>>>>>> + goto error_free_root;
>>>>>> INIT_KFIFO(vm->faults);
>>>>>> @@ -3039,18 +3063,11 @@ int amdgpu_vm_make_compute(struct
>>>>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>>>> if (r)
>>>>>> 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;
>>>>>> - }
>>>>>> + /* remove previous {pasid:vm} entry first */
>>>>>> + r = amdgpu_vm_set_pasid(adev, vm, 0);
>>>>>> + r = amdgpu_vm_set_pasid(adev, vm, pasid);
>>>>>> + if (r)
>>>>>> + goto unreserve_bo;
>>>>>> /* Check if PD needs to be reinitialized and do it before
>>>>>> * changing any other state, in case it fails.
>>>>>> @@ -3061,7 +3078,7 @@ int amdgpu_vm_make_compute(struct
>>>>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>>>> to_amdgpu_bo_vm(vm->root.bo),
>>>>>> false);
>>>>>> if (r)
>>>>>> - goto free_idr;
>>>>>> + goto free_pasid_entry;
>>>>>> }
>>>>>> /* Update VM state */
>>>>>> @@ -3078,7 +3095,7 @@ int amdgpu_vm_make_compute(struct
>>>>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>>>> r = amdgpu_bo_sync_wait(vm->root.bo,
>>>>>> AMDGPU_FENCE_OWNER_UNDEFINED, true);
>>>>>> if (r)
>>>>>> - goto free_idr;
>>>>>> + goto free_pasid_entry;
>>>>>> vm->update_funcs = &amdgpu_vm_cpu_funcs;
>>>>>> } else {
>>>>>> @@ -3088,31 +3105,14 @@ int amdgpu_vm_make_compute(struct
>>>>>> amdgpu_device *adev, struct amdgpu_vm *vm,
>>>>>> vm->last_update = NULL;
>>>>>> 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);
>>>>>> - vm->pasid = 0;
>>>>>> - }
>>>>>> -
>>>>>> /* 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;
>>>>>> +free_pasid_entry:
>>>>>> + amdgpu_vm_set_pasid(adev, vm, 0);
>>>>>> - 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;
>>>>>> @@ -3128,14 +3128,7 @@ 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_set_pasid(adev, vm, 0);
>>>>>> vm->is_compute_context = false;
>>>>>> }
>>>>>> @@ -3159,15 +3152,7 @@ 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_set_pasid(adev, vm, 0);
>>>>>> dma_fence_wait(vm->last_unlocked, false);
>>>>>> dma_fence_put(vm->last_unlocked);
>>>>>> @@ -3249,8 +3234,7 @@ void amdgpu_vm_manager_init(struct
>>>>>> amdgpu_device *adev)
>>>>>> adev->vm_manager.vm_update_mode = 0;
>>>>>> #endif
>>>>>> - idr_init(&adev->vm_manager.pasid_idr);
>>>>>> - spin_lock_init(&adev->vm_manager.pasid_lock);
>>>>>> + xa_init_flags(&adev->vm_manager.pasids, XA_FLAGS_LOCK_IRQ);
>>>>>> }
>>>>>> /**
>>>>>> @@ -3262,8 +3246,8 @@ void amdgpu_vm_manager_init(struct
>>>>>> amdgpu_device *adev)
>>>>>> */
>>>>>> void amdgpu_vm_manager_fini(struct amdgpu_device *adev)
>>>>>> {
>>>>>> - WARN_ON(!idr_is_empty(&adev->vm_manager.pasid_idr));
>>>>>> - idr_destroy(&adev->vm_manager.pasid_idr);
>>>>>> + WARN_ON(!xa_empty(&adev->vm_manager.pasids));
>>>>>> + xa_destroy(&adev->vm_manager.pasids);
>>>>>> amdgpu_vmid_mgr_fini(adev);
>>>>>> }
>>>>>> @@ -3332,13 +3316,13 @@ void amdgpu_vm_get_task_info(struct
>>>>>> amdgpu_device *adev, u32 pasid,
>>>>>> struct amdgpu_vm *vm;
>>>>>> unsigned long flags;
>>>>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, flags);
>>>>>> + xa_lock_irqsave(&adev->vm_manager.pasids, flags);
>>>>>> - vm = idr_find(&adev->vm_manager.pasid_idr, pasid);
>>>>>> + vm = xa_load(&adev->vm_manager.pasids, pasid);
>>>>>> if (vm)
>>>>>> *task_info = vm->task_info;
>>>>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, flags);
>>>>>> + xa_unlock_irqrestore(&adev->vm_manager.pasids, flags);
>>>>>> }
>>>>>> /**
>>>>>> @@ -3380,15 +3364,15 @@ bool amdgpu_vm_handle_fault(struct
>>>>>> amdgpu_device *adev, u32 pasid,
>>>>>> struct amdgpu_vm *vm;
>>>>>> int r;
>>>>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, irqflags);
>>>>>> - vm = idr_find(&adev->vm_manager.pasid_idr, pasid);
>>>>>> + xa_lock_irqsave(&adev->vm_manager.pasids, irqflags);
>>>>>> + vm = xa_load(&adev->vm_manager.pasids, pasid);
>>>>>> if (vm) {
>>>>>> root = amdgpu_bo_ref(vm->root.bo);
>>>>>> is_compute_context = vm->is_compute_context;
>>>>>> } else {
>>>>>> root = NULL;
>>>>>> }
>>>>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, irqflags);
>>>>>> + xa_unlock_irqrestore(&adev->vm_manager.pasids, irqflags);
>>>>>> if (!root)
>>>>>> return false;
>>>>>> @@ -3406,11 +3390,11 @@ bool amdgpu_vm_handle_fault(struct
>>>>>> amdgpu_device *adev, u32 pasid,
>>>>>> goto error_unref;
>>>>>> /* Double check that the VM still exists */
>>>>>> - spin_lock_irqsave(&adev->vm_manager.pasid_lock, irqflags);
>>>>>> - vm = idr_find(&adev->vm_manager.pasid_idr, pasid);
>>>>>> + xa_lock_irqsave(&adev->vm_manager.pasids, irqflags);
>>>>>> + vm = xa_load(&adev->vm_manager.pasids, pasid);
>>>>>> if (vm && vm->root.bo != root)
>>>>>> vm = NULL;
>>>>>> - spin_unlock_irqrestore(&adev->vm_manager.pasid_lock, irqflags);
>>>>>> + xa_unlock_irqrestore(&adev->vm_manager.pasids, irqflags);
>>>>>> if (!vm)
>>>>>> goto error_unlock;
>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>>>>> index ddb85a85cbba..31c467764162 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
>>>>>> @@ -359,8 +359,7 @@ struct amdgpu_vm_manager {
>>>>>> /* PASID to VM mapping, will be used in interrupt context to
>>>>>> * look up VM of a page fault
>>>>>> */
>>>>>> - struct idr pasid_idr;
>>>>>> - spinlock_t pasid_lock;
>>>>>> + struct xarray pasids;
>>>>>> };
>>>>>> struct amdgpu_bo_va_mapping;
>>>>>
>>>
>
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