| |
|
 |
|
 |
|
|
|
| |
|
|
xen-devel
Re: [Xen-devel] PCI BAR register space written with garbage in HVM guest
> <aside>
> What is pcifront/pciback's role for HVM guests exactly? I understand
None functionaly. The purpose is to "bind" the PCI devices to pciback
(or pcistub) so that no other kernel module usurps it and starts
utilizing it.
> that you "hide" the devices from the dom0 with pciback and it
> definately loads and does *something* when the HVM guest comes up, but
> accesses from the domU don't appear to go through it at all (I
> understand that it works with qemu somehow, but that channel too is
> not at all clear how it works...)
With HVM pciback is not used. You need an virtualization aware IOMMU to
pass through PCI devices to the guest. PCIback/PCI front is for PV
guests and on machine where you don't neccessarily have this fancy
IOMMU.
> I've looked through qemu enough to kind of understand that it's
> responsible for abstracting the PCI configuration space for the domU,
> but I don't really understand how accesses get channeled through to it
> from the domU. Does it use hypercalls somehow? Can someone explain
The Hypervisor gets "trapped" when an outb is made (look for
emulate_privileged_op function and specifically out).
Then it somehow injects the fault in QEMU which does the rest. I don't
remember the details of how it does thought :-(
> how this whole flow is supposed to work for PCI configuration space
> accesses?
> </aside>
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel
|
|
|
| |
|
Home