Re: [PATCH v2 22/32] drm/xe/svm: Split system allocator vma incase of madvise call

[Matthew Brost <matthew.brost@intel.com>]

On Mon, Apr 07, 2025 at 03:47:09PM +0530, Himal Prasad Ghimiray wrote:
> If the start or end of input address range lies within system allocator
> vma split the vma to create new vma's as per input range.
> 
> Signed-off-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_vm.c | 84 ++++++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/xe/xe_vm.h |  2 +
>  2 files changed, 86 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
> index 6e5ba58d475e..c7c012afe9eb 100644
> --- a/drivers/gpu/drm/xe/xe_vm.c
> +++ b/drivers/gpu/drm/xe/xe_vm.c
> @@ -4127,3 +4127,87 @@ void xe_vm_snapshot_free(struct xe_vm_snapshot *snap)
>  	}
>  	kvfree(snap);
>  }
> +
> +int xe_vm_alloc_madvise_vma(struct xe_vm *vm, uint64_t start, uint64_t range)
> +{
> +	struct xe_vma_ops vops;
> +	struct drm_gpuva_ops *ops = NULL;
> +	struct drm_gpuva_op *__op;
> +	bool is_cpu_addr_mirror = false;
> +	int err;
> +
> +	vm_dbg(&vm->xe->drm, "MADVISE IN: addr=0x%016llx, size=0x%016llx", start, range);
> +

lockdep assert for vm->lock, I assume we should have it in write mode
here.

> +	if (start & ~PAGE_MASK)
> +		start = ALIGN_DOWN(start, SZ_4K);
> +
> +	if (range & ~PAGE_MASK)
> +		range = ALIGN(range, SZ_4K);

We discussed this - not needed as UMD should align to GPU page size.

BTW - mismatch of PAGE_MASK, SZ_4K - they mean different things as
PAGE_SIZE depends CPU arch. We do this all over the driver but let's not
make this worse.

> +
> +	vm_dbg(&vm->xe->drm, "MADVISE_OPS_CREATE: addr=0x%016llx, size=0x%016llx", start, range);
> +	ops = drm_gpuvm_sm_map_ops_create(&vm->gpuvm, start, range,
> +					  DRM_GPUVM_SKIP_GEM_OBJ_VA_SPLIT_MADVISE,
> +					  NULL, start);
> +	if (IS_ERR(ops)) {
> +		err = PTR_ERR(ops);
> +		goto unwind_ops;

You don't need to unwind here, you can just return.

> +	}
> +
> +	if (list_empty(&ops->list)) {
> +		err = 0;
> +		goto free_ops;
> +	}
> +
> +	drm_gpuva_for_each_op(__op, ops) {
> +		struct xe_vma_op *op = gpuva_op_to_vma_op(__op);
> +
> +		if (__op->op == DRM_GPUVA_OP_REMAP) {
> +			if (xe_vma_is_cpu_addr_mirror(gpuva_to_vma(op->base.remap.unmap->va)))
> +				is_cpu_addr_mirror = true;
> +			else
> +				is_cpu_addr_mirror = false;
> +		}
> +
> +		if (__op->op == DRM_GPUVA_OP_MAP)
> +			op->map.is_cpu_addr_mirror = is_cpu_addr_mirror;
> +

I think this is right, but it took a minute to remember why this code is
needed. I think we need a comment here on is_cpu_addr_mirror usage.

> +		print_op(vm->xe, __op);
> +	}
> +
> +	xe_vma_ops_init(&vops, vm, NULL, NULL, 0);
> +	err = vm_bind_ioctl_ops_parse(vm, ops, &vops);
> +	if (err)
> +		goto unwind_ops;
> +
> +	xe_vm_lock(vm, false);
> +
> +	drm_gpuva_for_each_op(__op, ops) {
> +		struct xe_vma_op *op = gpuva_op_to_vma_op(__op);
> +		struct xe_vma *vma;
> +		struct xe_vma_mem_attr temp_attr;
> +
> +		if (__op->op == DRM_GPUVA_OP_UNMAP) {
> +			/* There should be no unmap */
> +			xe_assert(vm->xe, true);

xe_assert(vm->xe, true) will pop. How about...

XE_WARN_ON("UNEXPECTED UNMAP");

> +			xe_vma_destroy(gpuva_to_vma(op->base.unmap.va), NULL);
> +		} else if (__op->op == DRM_GPUVA_OP_REMAP) {
> +			vma = gpuva_to_vma(op->base.remap.unmap->va);
> +			cp_mem_attr(&temp_attr, &vma->attr);

See my comments about cp_mem_attr in a prior patch.

> +			xe_vma_destroy(gpuva_to_vma(op->base.remap.unmap->va), NULL);
> +		} else if (__op->op == DRM_GPUVA_OP_MAP) {
> +			vma = op->map.vma;
> +			cp_mem_attr(&vma->attr, &temp_attr);
> +		}

Also perhaps ref the comment above of why copying the attributes is
needed.

Matt

> +	}
> +
> +	xe_vm_unlock(vm);
> +	drm_gpuva_ops_free(&vm->gpuvm, ops);
> +	return 0;
> +
> +unwind_ops:
> +	vm_bind_ioctl_ops_unwind(vm, &ops, 1);
> +free_ops:
> +	if (ops)
> +		drm_gpuva_ops_free(&vm->gpuvm, ops);
> +	return err;
> +}
> diff --git a/drivers/gpu/drm/xe/xe_vm.h b/drivers/gpu/drm/xe/xe_vm.h
> index 99e164852f63..4e45230b7205 100644
> --- a/drivers/gpu/drm/xe/xe_vm.h
> +++ b/drivers/gpu/drm/xe/xe_vm.h
> @@ -171,6 +171,8 @@ static inline bool xe_vma_is_userptr(struct xe_vma *vma)
>  
>  struct xe_vma *xe_vm_find_vma_by_addr(struct xe_vm *vm, u64 page_addr);
>  
> +int xe_vm_alloc_madvise_vma(struct xe_vm *vm, uint64_t addr, uint64_t size);
> +
>  /**
>   * to_userptr_vma() - Return a pointer to an embedding userptr vma
>   * @vma: Pointer to the embedded struct xe_vma
> -- 
> 2.34.1
>