Re: [PATCH v1] drm/xe: Don't expose device attributes for VFs

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

On Sat, 2025-07-12 at 00:38 +0530, Raag Jadav wrote:
> Commit a7f87deac229 ("drm/xe: Default auto_link_downgrade status to
> false")
> tried to fix the side effect of xe_pcode_read() returning
> successfully
> without valid data-out value when xe->info.skip_pcode is set. Since
> this
> is true for IS_SRIOV_VF() cases, a much robust fix would be to not
> expose
> device attributes for VFs, which covers wider pcode mailbox users.

I'm not fully understanding your reasoning here. Why can't we just use
a check against skip_pcode in that case? VF might be the main user
there, but it isn't inconceivable that we will use that in other
scenarios too and then hit a similar problem of accessing an
uninitialized variable.

Thanks,
Stuart

> 
> Fixes: a7f87deac229 ("drm/xe: Default auto_link_downgrade status to
> false")
> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_device_sysfs.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/xe/xe_device_sysfs.c
> b/drivers/gpu/drm/xe/xe_device_sysfs.c
> index e5fd0cd537bc..8250aa4620ee 100644
> --- a/drivers/gpu/drm/xe/xe_device_sysfs.c
> +++ b/drivers/gpu/drm/xe/xe_device_sysfs.c
> @@ -259,8 +259,7 @@ auto_link_downgrade_status_show(struct device
> *dev, struct device_attribute *att
>  {
>         struct pci_dev *pdev = to_pci_dev(dev);
>         struct xe_device *xe = pdev_to_xe_device(pdev);
> -       /* default the auto_link_downgrade status to 0 */
> -       u32 val = 0;
> +       u32 val;
>         int ret;
>  
>         xe_pm_runtime_get(xe);
> @@ -297,6 +296,9 @@ int xe_device_sysfs_init(struct xe_device *xe)
>         struct device *dev = xe->drm.dev;
>         int ret;
>  
> +       if (IS_SRIOV_VF(xe))
> +               return 0;
> +
>         if (xe->d3cold.capable) {
>                 ret = sysfs_create_file(&dev->kobj,
> &dev_attr_vram_d3cold_threshold.attr);
>                 if (ret)