Re: [PATCH 10/11] drm/amdgpu: fix some more bug in amdgpu_gem_va_ioctl

["Khatri, Sunil" <sukhatri@amd.com>]

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On 11-03-2026 12:43 am, Christian König wrote:
> Some illegal combination of input flags were not checked and we need to
> take the PDEs into account when returning the fence as well.
>
> Signed-off-by: Christian König<christian.koenig@amd.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 76 +++++++++++--------------
>   1 file changed, 34 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index 88a21400ae09..98276b55ad3c 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -30,6 +30,7 @@
>   #include <linux/pagemap.h>
>   #include <linux/pci.h>
>   #include <linux/dma-buf.h>
> +#include <linux/dma-fence-unwrap.h>
>   
>   #include <drm/amdgpu_drm.h>
>   #include <drm/drm_drv.h>
> @@ -741,11 +742,10 @@ amdgpu_gem_va_update_vm(struct amdgpu_device *adev,
>   	struct dma_fence *fence;
>   	int r = 0;
>   
> -	/* Always start from the VM's existing last update fence. */
> -	fence = dma_fence_get(vm->last_update);
> -
> +	/* If the VM is not ready return only a stub. */
>   	if (!amdgpu_vm_ready(vm))
> -		return fence;
> +		return dma_fence_get_stub();
> +
>   
>   	/*
>   	 * First clean up any freed mappings in the VM.
> @@ -754,7 +754,7 @@ amdgpu_gem_va_update_vm(struct amdgpu_device *adev,
>   	 * schedules GPU work. If nothing needs clearing, @fence can remain as
>   	 * the original vm->last_update.
>   	 */
> -	r = amdgpu_vm_clear_freed(adev, vm, &fence);
> +	r = amdgpu_vm_clear_freed(adev, vm, &vm->last_update);
>   	if (r)
>   		goto error;
>   
> @@ -771,47 +771,34 @@ amdgpu_gem_va_update_vm(struct amdgpu_device *adev,
>   	if (r)
>   		goto error;
>   
> -	/*
> -	 * Decide which fence best represents the last update:
> -	 *
> -	 * MAP/REPLACE:
> -	 *   - For always-valid mappings, use vm->last_update.
> -	 *   - Otherwise, export bo_va->last_pt_update.
> -	 *
> -	 * UNMAP/CLEAR:
> -	 *   Keep the fence returned by amdgpu_vm_clear_freed(). If no work was
> -	 *   needed, it can remain as vm->last_pt_update.
> -	 *
> -	 * The VM and BO update fences are always initialized to a valid value.
> -	 * vm->last_update and bo_va->last_pt_update always start as valid fences.
> -	 * and are never expected to be NULL.
> -	 */
> -	switch (operation) {
> -	case AMDGPU_VA_OP_MAP:
> -	case AMDGPU_VA_OP_REPLACE:
> +	if ((operation == AMDGPU_VA_OP_MAP ||
> +	     operation == AMDGPU_VA_OP_REPLACE) &&
> +	    !amdgpu_vm_is_bo_always_valid(vm, bo_va->base.bo)) {
> +
>   		/*
> -		 * For MAP/REPLACE, return the page table update fence for the
> -		 * mapping we just modified. bo_va is expected to be valid here.
> +		 * For MAP/REPLACE of non per-VM BOs we need to sync to both the
> +		 * bo_va->last_pt_update and vm->last_update or otherwise we
> +		 * potentially miss the PDE updates.
>   		 */
> -		dma_fence_put(fence);
> -
> -		if (amdgpu_vm_is_bo_always_valid(vm, bo_va->base.bo))
> -			fence = dma_fence_get(vm->last_update);
> -		else
> -			fence = dma_fence_get(bo_va->last_pt_update);
> -		break;
> -	case AMDGPU_VA_OP_UNMAP:
> -	case AMDGPU_VA_OP_CLEAR:
> -	default:
> -		/* keep @fence as returned by amdgpu_vm_clear_freed() */
> -		break;
> +		fence = dma_fence_unwrap_merge(vm->last_update,
> +					       bo_va->last_pt_update);
> +		if (!fence) {
> +			/* As fallback in OOM situations */
> +			dma_fence_wait(vm->last_update, false);
> +			dma_fence_wait(bo_va->last_pt_update, false);
> +			fence = dma_fence_get_stub();
> +		}
> +	} else {
> +		fence = dma_fence_get(vm->last_update);
>   	}
>   
> +	return fence;
> +
>   error:
>   	if (r && r != -ERESTARTSYS)
>   		DRM_ERROR("Couldn't update BO_VA (%d)\n", r);
>   
> -	return fence;
> +	return dma_fence_get(vm->last_update);
>   }
>   
>   int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
> @@ -832,7 +819,6 @@ int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
>   	struct amdgpu_bo_va *bo_va;
>   	struct drm_syncobj *timeline_syncobj = NULL;
>   	struct dma_fence_chain *timeline_chain = NULL;
> -	struct dma_fence *fence;
>   	struct drm_exec exec;
>   	uint64_t vm_size;
>   	int r = 0;
> @@ -884,6 +870,10 @@ int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
>   		return -EINVAL;
>   	}
>   
> +	if (args->flags & AMDGPU_VM_DELAY_UPDATE &&
> +	    args->vm_timeline_syncobj_out)
> +		return -EINVAL;
> +
>   	if ((args->operation != AMDGPU_VA_OP_CLEAR) &&
>   	    !(args->flags & AMDGPU_VM_PAGE_PRT)) {
>   		gobj = drm_gem_object_lookup(filp, args->handle);
> @@ -973,11 +963,13 @@ int amdgpu_gem_va_ioctl(struct drm_device *dev, void *data,
>   	 * that represents the last relevant update for this mapping. This
>   	 * fence can then be exported to the user-visible VM timeline.
>   	 */
> -	if (!r && !(args->flags & AMDGPU_VM_DELAY_UPDATE) && !adev->debug_vm) {
> +	if (!r && !(args->flags & AMDGPU_VM_DELAY_UPDATE) &&
> +	    (!adev->debug_vm || timeline_syncobj)) {
> +		struct dma_fence *fence;
why to declare it here within the block. If i am not wrong we should 
have declaration first thing in the function as it was before?

Other than that small nitpick looks good to me.

Acked-by: Sunil Khatri <sunil.khatri@amd.com>

Regards
Sunil khatri


> +
>   		fence = amdgpu_gem_va_update_vm(adev, &fpriv->vm, bo_va,
>   						args->operation);
> -
> -		if (timeline_syncobj && fence) {
> +		if (timeline_syncobj) {
>   			if (!args->vm_timeline_point) {
>   				/* Replace the existing fence when no point is given. */
>   				drm_syncobj_replace_fence(timeline_syncobj,

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