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

[Felix Kuperjans <felix.kuperjans@xxxxxx>]

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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