On Tue, 19 Jul 2016 11:22:29 -0600
Alex Williamson <alex.william...@redhat.com> wrote:
> On Tue, 19 Jul 2016 17:12:45 +0000
> Spenser Gilliland <spenser.gillil...@xilinx.com> wrote:
>
> > Hi,
> >
> > I noticed your patches "vfio: add pcie extended capability support" and
> > "vfio/pci: Hide SR-IOV capability" have gone into qemu mainline. These
> > look really good, and thanks so much for doing these.
> >
> > I was wondering if there were any side effects to removing the
> > pci_bus_is_express check on line 1776 of hw/vfio/pci.c .
> >
> > /* Only add extended caps if we have them and the guest can see them */
> > - if (!pci_is_express(pdev) || !pci_bus_is_express(pdev->bus) ||
> > + if (!pci_is_express(pdev) ||
> > !pci_get_long(pdev->config + PCI_CONFIG_SPACE_SIZE)) {
> > return 0;
> > }
> >
> > I'm asking because it looks like the defaults for libvirt/OpenStack are to
> > create a "hostdev" stanza in the libvirt xml to define this pass through
> > condition. However, it also appears that the "hostdev" stanza only
> > supports pci-bridge bus connections. Thus, it's not easily possible to use
> > this patch in a libvirt/OpenStack environment as the bus is technically a
> > non-express bus. It looks like adding PCIe bus support to
> > libvirt/OpenStack may be a lot more effort than a simple workaround here.
> >
> > I have tested this on my local system and it does work as intended for my
> > use case. The following is from an OpenStack VM and shows that the 0x340
> > extended configuration space is passed through correctly. I've also done
> > testing which uses this space and the results are positive.
>
> If the bus is not express then extended capabilities on the device
> should not be accessible, this would be a QEMU bug for allowing it.
> Cc'ing Marcel for that. Thanks,
In fact, I've tried to fix this multiple times:
https://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05384.html
https://lists.nongnu.org/archive/html/qemu-devel/2015-11/msg02422.html
https://lists.nongnu.org/archive/html/qemu-devel/2016-01/msg03259.html
Yet the patch remains unapplied :(
