[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....@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