RE: [PATCH] VT-d: Tylersburg errata apply to further steppings

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Tuesday, August 3, 2021 7:14 PM
> 
> While for 5500 and 5520 chipsets only B3 and C2 are mentioned in the
> spec update, X58's also mentions B2, and searching the internet suggests
> systems with this stepping are actually in use. Even worse, for X58
> erratum #69 is marked applicable even to C2. Split the check to cover
> all applicable steppings and to also report applicable errata numbers in
> the log message. The splitting requires using the DMI port instead of
> the System Management Registers device, but that's then in line (also
> revision checking wise) with the spec updates.
> 
> Fixes: 6890cebc6a98 ("VT-d: deal with 5500/5520/X58 errata")
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

> ---
> As to disabling just interrupt remapping (as the initial version of the
> original patch did) vs disabling the IOMMU as a whole: Using a less
> heavy workaround would of course be desirable, but then we need to
> ensure not to misguide the tool stack about the state of the system. It
> uses the PHYSCAP_directio sysctl output to determine whether PCI pass-
> through can be made use of, yet that flag is driven by "iommu_enabled"
> alone, without regard to the setting of "iommu_intremap".
> 
> --- a/xen/drivers/passthrough/vtd/quirks.c
> +++ b/xen/drivers/passthrough/vtd/quirks.c
> @@ -268,26 +268,42 @@ static int __init parse_snb_timeout(cons
>  }
>  custom_param("snb_igd_quirk", parse_snb_timeout);
> 
> -/* 5500/5520/X58 Chipset Interrupt remapping errata, for stepping B-3.
> - * Fixed in stepping C-2. */
> +/*
> + * 5500/5520/X58 chipset interrupt remapping errata, for steppings B2 and
> B3.
> + * Fixed in stepping C2 except on X58.
> + */
>  static void __init tylersburg_intremap_quirk(void)
>  {
> -    uint32_t bus, device;
> +    unsigned int bus;
>      uint8_t rev;
> 
>      for ( bus = 0; bus < 0x100; bus++ )
>      {
> -        /* Match on System Management Registers on Device 20 Function 0 */
> -        device = pci_conf_read32(PCI_SBDF(0, bus, 20, 0), PCI_VENDOR_ID);
> -        rev = pci_conf_read8(PCI_SBDF(0, bus, 20, 0), PCI_REVISION_ID);
> +        /* Match on DMI port (Device 0 Function 0) */
> +        rev = pci_conf_read8(PCI_SBDF(0, bus, 0, 0), PCI_REVISION_ID);
> 
> -        if ( rev == 0x13 && device == 0x342e8086 )
> +        switch ( pci_conf_read32(PCI_SBDF(0, bus, 0, 0), PCI_VENDOR_ID) )
>          {
> +        default:
> +            continue;
> +
> +        case 0x34038086: case 0x34068086:
> +            if ( rev >= 0x22 )
> +                continue;
>              printk(XENLOG_WARNING VTDPREFIX
> -                   "Disabling IOMMU due to Intel 5500/5520/X58 Chipset 
> errata #47,
> #53\n");
> -            iommu_enable = 0;
> +                   "Disabling IOMMU due to Intel 5500/5520 chipset errata 
> #47 and
> #53\n");
> +            iommu_enable = false;
> +            break;
> +
> +        case 0x34058086:
> +            printk(XENLOG_WARNING VTDPREFIX
> +                   "Disabling IOMMU due to Intel X58 chipset %s\n",
> +                   rev < 0x22 ? "errata #62 and #69" : "erratum #69");
> +            iommu_enable = false;
>              break;
>          }
> +
> +        break;
>      }
>  }
>