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

["G.R." <firemeteor@xxxxxxxxxxxxxxxxxxxxx>]

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.

>
>>
>> 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

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel