Re: [Xen-devel] [PATCH] VTD/Intremap: Disable Intremap on Chipset 5500/5520/X58 due to errata

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.01.13 at 00:27, Malcolm Crossley <malcolm.crossley@xxxxxxxxxx> wrote:
> http://www.intel.com/content/www/us/en/chipsets/5520-and-5500-chipset-ioh-specific
>  
> ation-update.html
> 
> Stepping B-3 has two errata (#47 and #53) related to Interrupt
> remapping, to which the workaround is for the BIOS to completely disable
> interrupt remapping.  These errata are fixed in stepping C-2.
> 
> Unfortunately this chipset is very common and many BIOSes are not
> disabling remapping.  We can detect this in Xen and prevent turning on
> remapping in the first place.  However, this will turn VT-d off on many
> systems by default.
> 
> Users who still wish to use VT-d can use iommu=force if they are happy
> exposing the associated security risk.
> 
> Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> 
> diff -r 35a0556a7f76 -r ee475f0e6aeb xen/drivers/passthrough/vtd/quirks.c
> --- a/xen/drivers/passthrough/vtd/quirks.c
> +++ b/xen/drivers/passthrough/vtd/quirks.c
> @@ -244,6 +244,29 @@ void vtd_ops_postamble_quirk(struct iomm
>      }
>  }
>  
> +/* 5500/5520/X58 Chipset Interrupt remapping errata, for stepping B-3.
> + * Fixed in stepping C-2. */
> +void __init tylersburg_intremap_quirk(void)
> +{
> +    uint32_t bus, device;
> +    uint8_t rev;
> +
> +    for ( bus = 0; bus < 0x100; bus++ )
> +    {
> +        /* Match on System Management Registers on Device 20 Function 0 */
> +        device = pci_conf_read32(0, bus, 20, 0, PCI_VENDOR_ID);
> +        rev = pci_conf_read8(0, bus, 20, 0, PCI_REVISION_ID);
> +
> +        if ( rev == 0x13 && device == 0x342e8086 )
> +        {
> +            dprintk(XENLOG_INFO VTDPREFIX,
> +                    "Disabling Interrupt Remapping due to Intel 
> 5500/5520/X58 Chipset errata #47, #53\n");
> +            iommu_intremap = 0;

Unless it is guaranteed that no system with this chipset can have
x2APIC, I don't think this is right. For one, this happens way too
late (namely after x2apic_bsp_setup()). And second, if you move
this earlier, such systems with x2APIC pre-enabled won't boot
anymore.

Jan

> +            break;
> +        }
> +    }
> +}
> +
>  /* initialize platform identification flags */
>  void __init platform_quirks_init(void)
>  {
> @@ -264,6 +287,9 @@ void __init platform_quirks_init(void)
>  
>      /* ioremap IGD MMIO+0x2000 page */
>      map_igd_reg();
> +
> +    /* Tylersburg interrupt remap quirk */
> +    tylersburg_intremap_quirk();
>  }
>  
>  /*
> 
> _______________________________________________
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> Xen-devel@xxxxxxxxxxxxx 
> http://lists.xen.org/xen-devel 




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