Bug 408953

Summary:	app-emulation/qemu-kvm-1.0-r3: Interrupt remapping for PCI Passthrough Support is unimplemented on AMD Processors
Product:	Gentoo Linux	Reporter:	Richard Yao (RETIRED) <ryao>
Component:	[OLD] Unspecified	Assignee:	Doug Goldstein (RETIRED) <cardoe>
Status:	RESOLVED UPSTREAM
Severity:	normal
Priority:	Normal
Version:	unspecified
Hardware:	AMD64
OS:	Linux
Whiteboard:
Package list:		Runtime testing required:	---

Description Richard Yao (RETIRED) gentoo-dev

2012-03-20 06:30:03 UTC

https://lkml.org/lkml/2011/7/14/238

Currently, it is necessary to load the kvm module with allow_unsafe_assigned_interrupts=1 in order to do PCI Passthrough on AMD hardware, which can cause the guest to crash the host OS. We should modify the kernel component to use the IOMMU for interrupt remapping to fix this.

Comment 1 Doug Goldstein (RETIRED) gentoo-dev

2012-07-08 20:56:39 UTC

What you're looking for here is the VFIO branch where this work is happening. It looks like it has some potential to land in Linux 3.6 and QEMU 1.2. But until then, the current stuff in the kernel is totally wrong and busted because AMD actually implements a PCIe<->PCI bridge and as such the IOMMU can't really see beyond the bridge and deal with IRQs correctly.

The result is a complicated solution that is slowly taking shape but should really be discussed upstream.