On Wed, 2011-11-02 at 11:39 +1030, Rusty Russell wrote: > On Tue, 1 Nov 2011 14:42:23 +0200, "Michael S. Tsirkin" <[email protected]> > wrote: > > On Tue, Nov 01, 2011 at 02:33:33PM +0200, Sasha Levin wrote: > > > Unless Michael pointed this patch out, it would have broken (at least) > > > the kvm tool in a non obvious way which would require a rather long > > > session of 'git bisect' to figure out whats wrong. > > I assumed not, until QEMU provided the second BAR it would simply fall > back. Or am I completely misunderstanding?
QEMU uses two bars within each virtio-pci device. First one (BAR 0) is the PIO config BAR, and the second one (BAR 1) is the MSI-X BAR used for the MSI-X table and the PBA. Since the PCI spec allows you to have the MSI-X table and the PBA in completely different regions pointed by two different BARs, we did so in kvm tools and have BAR 1 pointing to the MSI-X table, and BAR 2 pointing to the PBA ( - we *already* provided the second BAR and used it for something else). This means that with this patch, we'd load BAR 2 and use it as the config space, instead of the PBA table which it really represents. -- Sasha. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
