Ping: [PATCH] VT-d: constrain IGD check

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.02.2023 10:51, Jan Beulich wrote:
> Marking a DRHD as controlling an IGD isn't very sensible without
> checking that at the very least it's a graphics device that lives at
> 0000:00:02.0. Re-use the reading of the class-code to control both the
> clearing of "gfx_only" and the setting of "igd_drhd_address".
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Kevin?

Thanks, Jan

> ---
> This way we also read the class code when we don't really need it, but
> I think that's tolerable, and the simpler logic is preferable. The more
> that with Marek's proposed patch, adjusted as suggested, we'd read
> vendor and device IDs unconditionally for all devices (enumerated for a
> DRHD) anyway.
> 
> --- a/xen/drivers/passthrough/vtd/dmar.c
> +++ b/xen/drivers/passthrough/vtd/dmar.c
> @@ -391,15 +391,12 @@ static int __init acpi_parse_dev_scope(
>  
>              if ( drhd )
>              {
> -                if ( (seg == 0) && (bus == 0) && (path->dev == 2) &&
> -                     (path->fn == 0) )
> -                    igd_drhd_address = drhd->address;
> -
> -                if ( gfx_only &&
> -                     pci_conf_read8(PCI_SBDF(seg, bus, path->dev, path->fn),
> +                if ( pci_conf_read8(PCI_SBDF(seg, bus, path->dev, path->fn),
>                                      PCI_CLASS_DEVICE + 1) != 0x03
>                                      /* PCI_BASE_CLASS_DISPLAY */ )
>                      gfx_only = false;
> +                else if ( !seg && !bus && path->dev == 2 && !path->fn )
> +                    igd_drhd_address = drhd->address;
>              }
>  
>              break;