Re: [PATCH v8 06/10] drm/xe/vf: Add bounds checking for queried GGTT base and size

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] drm/xe/vf: GGTT alignment uses CPU PAGE_SIZE breaking cross-page-size VMs
--

commit 974f2713618cba9d92f6442eb0ec21fab7f11630
Author: Satyanarayana K V P <satyanarayana.k.v.p@intel.com>

drm/xe/vf: Add bounds checking for queried GGTT base and size

This commit adds explicit bounds checks for GGTT base and size queried from
the PF. This is intended to detect and reject invalid configuration data to
prevent protocol violations and protect VF initialization.

> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> index 81d68fe5ad7cd..53db4cf9d656b 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_vf.c
[ ... ]
> @@ -486,26 +487,62 @@ u32 xe_gt_sriov_vf_gmdid(struct xe_gt *gt)
>  	return value;
>  }
>  
> +static u64 vf_get_ggtt_alignment(struct xe_gt *gt)
> +{
> +	return PAGE_SIZE;

[Severity: High]
Will this break initialization in cross-page-size virtualization environments
(e.g., a 4KB host and 64KB guest, which is standard on ARM64 and PPC64)?

In such a configuration, the PF driver running on the host allocates a
4KB-aligned GGTT partition. The VF driver running in the guest uses its own
OS PAGE_SIZE (64KB) for alignment checks.

It receives the 4KB-aligned start_query from the PF, aligns it up to 64KB,
and aligns the end down to 64KB. This artificially shrinks the GGTT window.

If the allocated GGTT size is smaller than the alignment difference,
end <= start evaluates to true, and the VF aborts initialization with
-ERANGE.

Should this alignment check use the hardware page size (e.g., XE_PAGE_SIZE)
instead of the CPU page size?

> +}
> +
>  static int vf_get_ggtt_info(struct xe_gt *gt)
>  {
[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260915071159.51402-12-satyanarayana.k.v.p@intel.com?part=6