Re: [Xen-devel] gfx-passthrough conflict with pxe booting?

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Aug 07, 2013 at 09:09:56PM +0800, G.R. wrote:
> On Wed, Aug 7, 2013 at 7:20 PM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> > On Wed, Aug 07, 2013 at 06:12:57PM +0800, G.R. wrote:
> >> A quick update about the root cause of this issue:
> >> The rombios BIOS used in xen restrict itself to i440FX emulated by Bochs / 
> >> qemu.
> >> With gfx-passthrough, the pci-host bridge in the domU is replaced by
> >> the device in the host machine.
> >> This makes PCI emulation fail.
> >> The issue can be fixed by simply commenting out this line:
> >>
> >> diff --git a/tools/firmware/rombios/rombios.c 
> >> b/tools/firmware/rombios/rombios.c
> >> index 80980b6..e9c5c4a 100644
> >> --- a/tools/firmware/rombios/rombios.c
> >> +++ b/tools/firmware/rombios/rombios.c
> >> @@ -220,7 +220,7 @@
> >>  // define this if you want to make PCIBIOS working on a specific bridge 
> >> only
> >>  // undef enables PCIBIOS when at least one PCI device is found
> >>  // i440FX is emulated by Bochs and QEMU
> >> -#define PCI_FIXED_HOST_BRIDGE 0x12378086 ;; i440FX PCI bridge
> >> +//#define PCI_FIXED_HOST_BRIDGE 0x12378086 ;; i440FX PCI bridge
> >>
> >>  // #20  is dec 20
> >>  // #$20 is hex 20 = 32
> >>
> >
> > Thanks for the analysis and the workaround!
> >
> > I wonder what kind of side-effects this has (might have).. disabling the 
> > fixed i440FX host bridge..
> > I assume in your case there was no other issues introduced by the change? 
> > And PXE boot started working with PCI/GPU passthru..
> >
> > -- Pasi
> 
> There should be no negative side-effect.
> This is only a self restriction that disable PCIBIOS on unknown HW platform.
> Not sure why this is introduced in the first place.
> 

Hello,

Does this problem still happen with Xen 4.4 and/or unstable? 


Thanks,

-- Pasi

> >
> >>
> >> On Wed, Apr 10, 2013 at 9:54 PM, G.R. <firemeteor@xxxxxxxxxxxxxxxxxxxxx> 
> >> wrote:
> >> > Hi developers,
> >> >
> >> > I just discovered that with gfx-passthrough=1, the iPXE simply does not 
> >> > work.
> >> > It seems that no NIC is detected by iPXE -- ifstat shows nothing.
> >> > I'm on xen-4.2.1 release, with some IGD passthrough related patches.
> >> > I would like to check if this is a common issue, can anybody help?
> >> >
> >> > Thanks,
> >> > Timothy
> >>
> >> _______________________________________________
> >> Xen-devel mailing list
> >> Xen-devel@xxxxxxxxxxxxx
> >> http://lists.xen.org/xen-devel

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