On Mon, Aug 22, 2011 at 09:54:50AM +0930, Rusty Russell wrote: > On Fri, 19 Aug 2011 18:23:35 +0300, "Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote: > > On Sat, Aug 13, 2011 at 11:51:01AM +0300, Sasha Levin wrote: > > > The MAC of a virtio-net device is located at the first field of the device > > > specific header. This header is located at offset 20 if the device doesn't > > > support MSI-X or offset 24 if it does. > > > > > > Current code in virtnet_probe() used to probe the MAC before checking for > > > MSI-X, which means that the read was always made from offset 20 regardless > > > of whether MSI-X in enabled or not. > > > > > > This patch moves the MAC probe to after the detection of whether MSI-X is > > > enabled. This way the MAC will be read from offset 24 if the device indeed > > > supports MSI-X. > > > > > > Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx> > > > Cc: Michael S. Tsirkin <mst@xxxxxxxxxx> > > > Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx > > > Cc: netdev@xxxxxxxxxxxxxxx > > > Cc: kvm@xxxxxxxxxxxxxxx > > > Signed-off-by: Sasha Levin <levinsasha928@xxxxxxxxx> > > > > I am not sure I see a bug in virtio: the config pace layout simply > > changes as msix is enabled and disabled (and if you look at the latest > > draft, also on whether 64 bit features are enabled). > > It doesn't depend on msix capability being present in device. > > > > The spec seems to be explicit enough: > > If MSI-X is enabled for the device, two additional fields immediately > > follow this header. > > > > So I'm guessing the bug is in kvm tools which assume > > same layout for when msix is enabled and disabled. > > qemu-kvm seems to do the right thing so the device > > seems to get the correct mac. > > So, the config space moves once MSI-X is enabled? In which case, it > should say "ONCE MSI-X is enabled..." > > Thanks, > Rusty. Yes. Or maybe 'WHEN' - since if MSI-X is disabled again, it moves back. Let's update the spec to make it clearer? -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
