Re: [v2 19/31] drm/xe/svm: Determine a vma is backed by device memory

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

On Tue, Apr 09, 2024 at 04:17:30PM -0400, Oak Zeng wrote:
> With system allocator, a userptr can now be back by device
> memory also. Introduce a helper function xe_vma_is_devmem
> to determine whether a vma is backed by device memory.
> 
> Signed-off-by: Oak Zeng <oak.zeng@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_pt.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> index 846e896edcb5..525092111be9 100644
> --- a/drivers/gpu/drm/xe/xe_pt.c
> +++ b/drivers/gpu/drm/xe/xe_pt.c
> @@ -577,6 +577,17 @@ static const struct xe_pt_walk_ops xe_pt_stage_bind_ops = {
>  	.pt_entry = xe_pt_stage_bind_entry,
>  };
>  
> +static bool xe_vma_is_devmem(struct xe_vma *vma)

At some point we probably want to scrub the driver as we intermix
devmem, vram, and lmem nomenclature. I think in case we mean the same
thing too. Anwyays that is a little out of scope here.

> +{
> +	if (xe_vma_is_userptr(vma)) {
> +		struct xe_userptr_vma *uvma = to_userptr_vma(vma);
> +		return uvma->userptr.is_device_pages;

Helper itself LGTM. Maybe promote to xe_vm.c/xe_vm.h?

Also consider other options rather than userptr.is_device_pages flag
here (e.g. look for buddy blocks, check a gpuvm flags, etc...). Can live
with a flag but we can do without it, great.

Matt

> +	} else {
> +		struct xe_bo *bo = xe_vma_bo(vma);
> +		return bo && (xe_bo_is_vram(bo) || xe_bo_is_stolen_devmem(bo));
> +	}
> +}
> +
>  /**
>   * xe_pt_stage_bind() - Build a disconnected page-table tree for a given address
>   * range.
> @@ -601,8 +612,7 @@ xe_pt_stage_bind(struct xe_tile *tile, struct xe_vma *vma,
>  {
>  	struct xe_device *xe = tile_to_xe(tile);
>  	struct xe_bo *bo = xe_vma_bo(vma);
> -	bool is_devmem = !xe_vma_is_userptr(vma) && bo &&
> -		(xe_bo_is_vram(bo) || xe_bo_is_stolen_devmem(bo));
> +	bool is_devmem = xe_vma_is_devmem(vma);
>  	struct xe_res_cursor curs;
>  	struct xe_pt_stage_bind_walk xe_walk = {
>  		.base = {
> -- 
> 2.26.3
>