On 04/08/2012 05:42 PM, Michael S. Tsirkin wrote: > On Sun, Apr 08, 2012 at 05:01:36PM +0300, Avi Kivity wrote: > > On 04/08/2012 04:53 PM, Michael S. Tsirkin wrote: > > > On Sun, Apr 08, 2012 at 04:41:27PM +0300, Avi Kivity wrote: > > > > On 04/08/2012 04:30 PM, Michael S. Tsirkin wrote: > > > > > On Sun, Apr 08, 2012 at 04:24:11PM +0300, Avi Kivity wrote: > > > > > > On 04/08/2012 04:21 PM, Michael S. Tsirkin wrote: > > > > > > > On Sun, Apr 08, 2012 at 04:18:29PM +0300, Avi Kivity wrote: > > > > > > > > On 04/08/2012 04:17 PM, Michael S. Tsirkin wrote: > > > > > > > > > > > > > > > > > > > > Don't we FLR the device, which ought to disable MSI on the real device? > > > > > > > > > > > > > > > > > > AFAIK we call pci_reset, which saves device state, does an FLR > > > > > > > > > and then restores the state. I think this might include msi as well. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Then that is wrong as well, no? > > > > > > > > > > > > > > Not as such assuming we disable msi/msix first :) > > > > > > > > > > > > I think we need to fix both, no? > > > > > > > > > > Isn't this what this patch does? > > > > > > > > If we change pci_reset() (or a variant that we call) to reset MSI, and > > > > update qemu to synchronize from the device after pci_reset(), then we > > > > achieve the same result, in a different way. > > > > > > MSI vectors are set up by kvm in the host. So we should not > > > abruptly drop that by a sysfs write: would need to > > > synchronise with kvm. Once we do, there's nothing left > > > for pci_reset to do. > > > > 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. > > set emulated register to hardware value > > Yes, I see what you are trying to say now. > Unfortunately that's not enough: we also > need to restore the registers afterwards for > device to become useful again. I guess this is correct for the MSIX BAR. But is it correct for MSIX enable/disable? > Doing this in kernel seems more robust, otherwise > we risk losing the device if qemu gets killed > before it has restored the registers. Doesn't the driver have to enable MSIX if it attaches to the device at that point, anyway? > > > > Since reset can change other config space registers, we achieve > > > > correctness for more of them. > > > > > > Which other registers do you have in mind? > > > > BARs for example. We may have our own reset for this, but isn't copying > > the hardware values more trustworthy? > > BAR values in host and guest are unrelated. > If pci_reset didn't restore BAR values we won't > be able to operate the device. > Right. I guess candidates are those that are initialized with assigned_dev_emulate_config_*()? Hard to see which ones because they're mass initialized. -- 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
