Re: Source of guest-physical address in PCI BAR for HVM domain?

[Samuel Thibault <samuel.thibault@eu.citrix.com>]

David Stone, le Fri 04 Jan 2008 13:25:47 -0500, a écrit :
> > > So I guess this the PCI config-space write to set the BAR is passed to
> > > qemu-dm as a command from the hypervisor
> >
> > Yes.
> 
> But doesn't qemu act as the BIOS for HVM domains?

Yes.

> Why would the hypervisor be doing the initial PCI BAR setup?

The hypervisor does nothing but retransmit what the HVM domain performs.
Remember that instructions of the qemu BIOS are run in the HVM domain,
not in qemu, which only gets triggered when the BIOS actually I/O ports
or memory.

> > > If so, shouldn't the early PCI configuration from the BIOS be coming
> > > from qemu itself?
> >
> > It is. It's odd you have troubles so early in the boot, is your
> > configuration a bit special in any way?
> 
> Yes, I didn't mention the most important part: the device in question
> is a physical PCI device (a PCI Express graphics card) that I am
> passing through to the Windows 2003 guest domain via VT-d.  (The VT-d
> support generally works for me because I can pass a PCI NIC through no
> problem.)  (I realize VT-d'ing a PCI-XP graphics card is
> experimental...but that's what I'm doing, experimenting...).

Then maybe the qemu BIOS has troubles with that device?

Samuel