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

[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.

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;
-- 
2.35.1