On 04/08/2012 07:04 PM, Michael S. Tsirkin wrote: > On Sun, Apr 08, 2012 at 06:50:27PM +0300, Avi Kivity wrote: > > On 04/08/2012 06:46 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > I'm thinking about this flow: > > > > > > > > > > > > FLR the device > > > > > > for each emulated register > > > > > > read it from the hardware > > > > > > if different from emulated register: > > > > > > update the internal model (for example, disabling MSI in kvm if > > > > > > needed) > > > > > > > > > > If we do it this way we get back the problem this patch > > > > > is trying to solve: MSIX assigned while device > > > > > memory is disabled would cause unsupported request errors. > > > > > > > > Why is that? FLR would presumably disable MSI in the device, and this > > > > line would disable it in kvm as well. > > > > > > The bug is that device memory is disabled (FLR would do that) > > > while MSI is enabled in kvm. The fix is to > > > disable MSI in kvm first. > > > > Yes, no need to repeat. My question is whether my pseudo-code does the > > same > > It doesn't seem to: FLR (disabling memory) is followed > by MSI disable in kvm instead of the reverse. Ah, so the problem is the ordering? I see. > > and whether or not if it is better (when applied to all emulated > > config space). > > I'm not sure. > I would like to see an example of a register that you have > in mind. I went over the PCI registers and saw none that would be affected. > > > > > > Yes. I'm talking about things like enabling memory, setting up irq register, > > > etc though. Most of this setup is done by bios. > > > > I see. So should we have a pci_reset_function() variant that limits > > itself to restoring just those bits? > > We only need kernel to restore whatever qemu emulates, but > kernel doesn't know what that is. > What kind of interface do you have in mind? > The same as pci_reset_function(), but leaves MSI clear. I guess it's not worth it if the ordering problem is there. -- error compiling committee.c: too many arguments to function -- 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
