Re: [PATCH] drm/xe/pf: Fix MMIO access using PF view instead of VF view during migration

["Summers, Stuart" <stuart.summers@intel.com>]

On Wed, 2026-04-29 at 19:22 +0000, Shuicheng Lin wrote:
> pf_migration_mmio_save() and pf_migration_mmio_restore() initialize a
> local VF-specific MMIO view via xe_mmio_init_vf_view() but then pass
> &gt->mmio (the PF base) to all xe_mmio_read32()/xe_mmio_write32()
> calls instead of the local &mmio. This causes the PF own SW flag
> registers to be saved/restored rather than the target VF registers,
> silently corrupting migration state.
> 
> Use the VF MMIO view for all register accesses, matching the correct
> pattern used in pf_clear_vf_scratch_regs().
> 
> Fixes: b7c1b990f719 ("drm/xe/pf: Handle MMIO migration data as part
> of PF control")
> Cc: Michał Winiarski <michal.winiarski@intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
> Assisted-by: Claude:claude-opus-4.6
> Signed-off-by: Shuicheng Lin <shuicheng.lin@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_gt_sriov_pf_migration.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_gt_sriov_pf_migration.c
> b/drivers/gpu/drm/xe/xe_gt_sriov_pf_migration.c
> index 87a164efcc33..01fe03b9efe8 100644
> --- a/drivers/gpu/drm/xe/xe_gt_sriov_pf_migration.c
> +++ b/drivers/gpu/drm/xe/xe_gt_sriov_pf_migration.c
> @@ -385,10 +385,10 @@ static int pf_migration_mmio_save(struct xe_gt
> *gt, unsigned int vfid, void *buf
>  
>         if (xe_gt_is_media_type(gt))
>                 for (n = 0; n < MED_VF_SW_FLAG_COUNT; n++)
> -                       regs[n] = xe_mmio_read32(&gt->mmio,
> MED_VF_SW_FLAG(n));
> +                       regs[n] = xe_mmio_read32(&mmio,
> MED_VF_SW_FLAG(n));

Good to get feedback from Michal Wa/Michal Wi here, but I don't see any
usage of these MMIOs from the VF in the driver. Are these even exposed
to the VF? This seems unsafe from what I can see...

Can you show the error you are seeing specifically?

Thanks,
Stuart

>         else
>                 for (n = 0; n < VF_SW_FLAG_COUNT; n++)
> -                       regs[n] = xe_mmio_read32(&gt->mmio,
> VF_SW_FLAG(n));
> +                       regs[n] = xe_mmio_read32(&mmio,
> VF_SW_FLAG(n));
>  
>         return 0;
>  }
> @@ -407,10 +407,10 @@ static int pf_migration_mmio_restore(struct
> xe_gt *gt, unsigned int vfid,
>  
>         if (xe_gt_is_media_type(gt))
>                 for (n = 0; n < MED_VF_SW_FLAG_COUNT; n++)
> -                       xe_mmio_write32(&gt->mmio, MED_VF_SW_FLAG(n),
> regs[n]);
> +                       xe_mmio_write32(&mmio, MED_VF_SW_FLAG(n),
> regs[n]);
>         else
>                 for (n = 0; n < VF_SW_FLAG_COUNT; n++)
> -                       xe_mmio_write32(&gt->mmio, VF_SW_FLAG(n),
> regs[n]);
> +                       xe_mmio_write32(&mmio, VF_SW_FLAG(n),
> regs[n]);
>  
>         return 0;
>  }