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Re: [Xen-devel] XSA-36 / howto fix broken IVRS ACPI table

  • To: xen-devel@xxxxxxxxxxxxx
  • From: Hans Mueller <mcbeagle@xxxxxx>
  • Date: Tue, 23 Apr 2013 19:11:05 +0200
  • Delivery-date: Tue, 23 Apr 2013 17:11:34 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>


I got a patched BIOS (version F8c) from Gigabyte which removes the 2nd IOAPIC 
entry (for device 0000:00:00.1) from the IVRS table.

This causes Xen to enable per-device vector maps:
(XEN) AMD-Vi: IOMMU 0 Enabled.
(XEN) AMD-Vi: Enabling per-device vector maps
(XEN) I/O virtualisation enabled
(XEN)  - Dom0 mode: Relaxed
(XEN) Interrupt remapping enabled

However the problem seems not really to be fixed:
Interrupts generated within one domain can still harm other domains which at 
least causes the kernel within these other domains to disable interrupts.

Before going to investigate/debug this problem, I want to know if one IOAPIC 
is sufficient as the AMD 970 chipset seems to have one IOAPIC related to the 
northbridge and one for the southbridge.
The one currently enabled is the southbridge one (0000:00:14.0). Does it also 
support devices connected to the northbridge or needs the northbridge one to 
be enabled, too?
Are there other limitations/problems to expect regarding the disabled 
northbridge IOAPIC?

Thanks & best regards

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