[PATCH] drm/amdgpu: reset vm state machine after gpu reset(vram lost)

[Christian König]

Am 19.07.24 um 11:19 schrieb ZhenGuo Yin:
> [Why]
> Page table of compute VM in the VRAM will lost after gpu reset.
> VRAM won't be restored since compute VM has no shadows.
>
> [How]
> Use higher 32-bit of vm->generation to record a vram_lost_counter.
> Reset the VM state machine when the counter is not equal to current
> vram_lost_counter of the device.

Mhm, that was my original approach as well but we came to the conclusion 
that this shouldn't be necessary since loosing VRAM would result in the 
entity to become invalid as well.

Why is that necessary?

Regards,
Christian.

>
> Signed-off-by: ZhenGuo Yin <zhenguo.yin at amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index 3abfa66d72a2..fd7f912816dc 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -434,7 +434,7 @@ uint64_t amdgpu_vm_generation(struct amdgpu_device *adev, struct amdgpu_vm *vm)
>   	if (!vm)
>   		return result;
>   
> -	result += vm->generation;
> +	result += (vm->generation & 0xFFFFFFFF);
>   	/* Add one if the page tables will be re-generated on next CS */
>   	if (drm_sched_entity_error(&vm->delayed))
>   		++result;
> @@ -467,6 +467,12 @@ int amdgpu_vm_validate(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   	struct amdgpu_bo *shadow;
>   	struct amdgpu_bo *bo;
>   	int r;
> +	uint32_t vram_lost_counter = atomic_read(&adev->vram_lost_counter);
> +
> +	if ((vm->generation >> 32) != vram_lost_counter) {
> +		amdgpu_vm_bo_reset_state_machine(vm);
> +		vm->generation = (u64)vram_lost_counter << 32 | (vm->generation & 0xFFFFFFFF);
> +	}
>   
>   	if (drm_sched_entity_error(&vm->delayed)) {
>   		++vm->generation;
> @@ -2439,7 +2445,7 @@ int amdgpu_vm_init(struct amdgpu_device *adev, struct amdgpu_vm *vm,
>   	vm->last_update = dma_fence_get_stub();
>   	vm->last_unlocked = dma_fence_get_stub();
>   	vm->last_tlb_flush = dma_fence_get_stub();
> -	vm->generation = 0;
> +	vm->generation = (u64)atomic_read(&adev->vram_lost_counter) << 32;
>   
>   	mutex_init(&vm->eviction_lock);
>   	vm->evicting = false;