Re: [Xen-devel] About VT-d on ASUS P6T

[Felix Kuperjans <felix@xxxxxxxxxxxxxxxxxx>]

So there will be some devices that do not work while others work - can I
figure out which devices are affected by the incorrect RMRR?

In addition, only setting iommu=passtrough caused XEN to disable VT-d
completely, altough some devices actually can be passtroughed to the
domU perfectly.

Regards,
Felix

Am 12.05.2010 03:54, schrieb Han, Weidong:
> Your code changes just let xen not disable VT-d, but actually 
> "iommu=passthrough" avoids problems of incorrect RMRR. This option makes dom0 
> not use VT-d, therefore incorrect RMRR won't be used by device. But if you 
> assign the device whose RMRR incorrect to guest, it still causes problems. 
>
> Regards,
> Weidong
>
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Felix Kuperjans
> Sent: Tuesday, May 11, 2010 6:09 PM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-devel] About VT-d on ASUS P6T
>
> Hi,
>
> as I posted on xen-users, I've successfully used pci passtrough on an ASUS 
> P6T mainboard which is known to have really buggy RMRR tables.
>
> I needed the iommu=passtrough and iommu_inclusive_mapping=1 command line 
> options, combined with a little change to the RMRR parsing code:
>
> dmar.c:
>
> @@ -559,8 +558,7 @@
>              dprintk(XENLOG_WARNING VTDPREFIX,
>                  "  The RMRR (%"PRIx64", %"PRIx64") is incorrect!\n",
>                  rmrru->base_address, rmrru->end_address);
> -            xfree(rmrru);
> -            ret = -EFAULT;
> +            acpi_register_rmrr_unit(rmrru);
>          }
>          else
>          {
>
> This way, the condition that causes the error printed above, does not lead to 
> an abortion of VT-d code, but instead registers the RMRR unit as if it was 
> correct.
> VT-d is working properly afterwards and I've tested some devices successfully.
>
> Probably, you would prefer to choose the action based on some command line 
> option (like iommu_inclusive_mapping=1) instead of ignoring this error by 
> default.
>
> Regards,
> Felix
>
>
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