Re: [Xen-devel] PCI passthrough and 3.3.1/3.4.0

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 01/03/2009 11:16, "Andy Burns" <xen.lists@xxxxxxxxxxx> wrote:

>> Most passthrough work currently going on is in relation to HVM guests.
> 
> Heh, I thought my Q9450 cpu and X38 chipset were going to be
> sufficient for HVM I/O support, but ASUS have not enabled support for
> it in the BIOS, I don't suppose there's a well-known bit in a register
> on the X38 ICH9R that can be flipped to force VT-d on is there?

Unfortunately you need a VT-d aware BIOS because it is the BIOS which
describes the VT-d hardware to the hypervisor, via a set of in-memory info
tables. No BIOS support == no VT-d, despite the fact at the hardware level
the support may well be present and waiting to be used. Actually even some
BIOSes which do claim to support VT-d are pretty broken -- presumably it's
something vendors don't have comprehensive tests for as yet -- so you have
to be careful.

>> I'm currently thinking about freezing the tree at the end of March and
>> releasing late April or early May.
> 
> OK thanks, that's far enough away to tempt me to try Yuji's BAR
> alignment patches on CentOS in the meantime.

Yes, worth some experimentation I think. Also generally providing more info
on xen-devel about how PV passthru is failing for you may help get it fixed.
Even better if you can track down when it broke, who broke it, and try and
get help from them via direct plea. ;-)

 -- Keir



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