[Xen-devel] VT-d Stop working after XEN update

[JavMV <javier.manzano@xxxxxxxxxx>]

Hello, I was trying to achieve VGA-passthrough but I have encountered a
problem enabling VT-d on Xen-unstable,
I was able to use it in the past with the changeset 23350 but if I use the
changeset 23799 or greater this feature is automatically disabled,
so there must be some changes between those two changesets that provokes
VT-d crash on my computer.
Details below:

-Mother board: Intel DQ35MP.
-Bios version 1143 (the latest version available, it is from 2010).
-Options VT Technology and VT for directed I/O (VT-d) are enabled.
-Using the option iommu=force in grub entry

'# xm dmesg' output with *changeset 23799*:
   (XEN) [VT-D]dmar.c:456:   Non-existent device (0:2.1) is reported in this
DRHD\047s scope!
   (XEN) [VT-D]dmar.c:479:   The DRHD is invalid due to there are devices
under its scope are not PCI
   discoverable! Pls try option iommu=force or iommu=workaround_bios_bug if
you really want VT-d
   (XEN) Failed to parse ACPI DMAR.  Disabling VT-d.
   (XEN) Table is not found!
   (XEN) Using ACPI (MADT) for SMP configuration information
    ...
   (XEN) I/O virtualisation disabled
    ...
   (XEN) HVM: ASIDs disabled.
   (XEN) HVM: VMX enabled

'# xm dmesg' output with *changeset 23350*:
    ...
    (XEN) Intel VT-d Snoop Control not enabled.
    (XEN) Intel VT-d Dom0 DMA Passthrough not enabled.
    (XEN) Intel VT-d Queued Invalidation not enabled.
    (XEN) Intel VT-d Interrupt Remapping not enabled.
    (XEN) [VT-D]iommu.c:847: iommu_fault_status: Fault Overflow
    (XEN) [VT-D]iommu.c:850: iommu_fault_status: Primary Pending Fault
    (XEN) [VT-D]iommu.c:825: DMAR:[DMA Write] Request device [00:02.0] fault
addr ffffff000, iommu reg = fff16000
    ...
    (XEN) Enabling APIC mode:  Flat.  Using 1 I/O APICs
    (XEN) I/O virtualisation enabled 

I can see I/O enabled but all the VT-d features are disabled, so maybe
that's why with the last revision of XEN I can't have I/O virtualisation
enabled. Am I still able to use vga-passthru with this kind of output?

Thanks in advance

Javier


-----
JavMV
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