Re: PCI passthrough = NMIs

[Sheng Yang <sheng@linux.intel.com>]

On Tuesday 14 October 2008 12:39:52 Zwane Mwaikambo wrote:
> On Tue, 14 Oct 2008, Sheng Yang wrote:
> > On Monday 13 October 2008 23:04:34 Zwane Mwaikambo wrote:
> > > On Mon, 13 Oct 2008, Muli Ben-Yehuda wrote:
> > > > On Sun, Oct 12, 2008 at 11:09:14PM -0700, Zwane Mwaikambo wrote:
> > > > > Hi,
> > > > > 	I've been trying to get a Linux guest working with PCI passthrough
> > > > > of an ethernet card using the vtd branches. The device detection
> > > > > works and the guest reports a link, however as soon as i try and
> > > > > ping the guest it receives an NMI (i'm guessing this is PCI DMA
> > > > > related). Interrupt delivery to the guest looks fine (count
> > > > > increases at a low rate) and isn't shared with anything else on the
> > > > > host.
> > > > >
> > > > > Thanks for any hints.
> > > >
> > > > Anything in the host dmesg? Are you using VT-d?
> > >
> > > Yep using VT-d on an intel Q35, i get the following in order;
> > >
> > > pci 0000:11:0a.0: PCI INT A -> GSI 20 (level, low) -> IRQ 20
> > > DMAR:[DMA Read] Request device [00:1e.0] fault addr 7841000
> > > DMAR:[fault reason 06] PTE Read access is not set
> > > Uhhuh. NMI received for unknown reason a1.
> > > You have some hardware problem, likely on the PCI bus.
> > > Dazed and confused, but trying to continue
> > > DMAR:[DMA Write] Request device [00:1e.0] fault addr 0
> > > DMAR:[fault reason 05] PTE Write access is not set
> > > DMAR:[DMA Write] Request device [00:1e.0] fault addr 0
> > > DMAR:[fault reason 05] PTE Write access is not set
> >
> > Do you have VT-d enabled? Also reinstalled host kernel with KVM
> > upstream(we modified host kernel to support VT-d in KVM)? Look like VT-d
> > table is not set up... You can check what you got with "dmesg|grep DMAR".
>
> Yep, i have VT-d enabled in the BIOS, i also had to disable legacy USB in
> order to get Linux to boot. This is what i get on the host kernel;
>
> ACPI: DMAR 7F487CA8, 00C8 (r1 Intel  OEMDMAR   6040000 LOHR        1)
> DMAR:Host address width 36
> DMAR:DRHD (flags: 0x00000000)base: 0x00000000fed90000
> DMAR:DRHD (flags: 0x00000000)base: 0x00000000fed91000
> DMAR:DRHD (flags: 0x00000001)base: 0x00000000fed93000
> DMAR:RMRR base: 0x000000007f4e4000 end: 0x000000007f4f0000
>
> Although legacy USB not working would suggest that there are table entries
> already missing in the BIOS?

The VT-d table should be set up by KVM, but it's very strange that if you 
enable VT-d for native, USB can't work. If you sure you are using kernel 
compiled from KVM upstream, I think it maybe a BIOS issue...

--
regards
Yang, Sheng