On Tue, Dec 12, 2023 at 11:01:53AM +0800, Jason Wang wrote:
> On Tue, Dec 12, 2023 at 12:37 AM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> >
> > On Fri, Dec 08, 2023 at 04:07:54PM +0900, David Stevens wrote:
> > > If a virtio_pci_device supports native PCI power management and has the
> > > No_Soft_Reset bit set, then skip resetting and reinitializing the device
> > > when suspending and restoring the device. This allows system-wide low
> > > power states like s2idle to be used in systems with stateful virtio
> > > devices that can't simply be re-initialized (e.g. virtio-fs).
> > >
> > > Signed-off-by: David Stevens <stevensd@xxxxxxxxxxxx>
> >
> > tagged, thanks!
> > I'm still debating with myself whether we can classify this
> > as a bugfix ... better not risk it I guess.
>
> It might be suitable if there's a hypervisor that advertises
> no_soft_reset (but it seems Qemu doesn't).
>
> Thanks
Yea... so a bugfix but no rush to merge it I think.
> >
> > > ---
> > > v1 -> v2:
> > > - Check the No_Soft_Reset bit
> > >
> > > drivers/virtio/virtio_pci_common.c | 34 +++++++++++++++++++++++++++++-
> > > 1 file changed, 33 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> > > index c2524a7207cf..3a95ecaf12dc 100644
> > > --- a/drivers/virtio/virtio_pci_common.c
> > > +++ b/drivers/virtio/virtio_pci_common.c
> > > @@ -492,8 +492,40 @@ static int virtio_pci_restore(struct device *dev)
> > > return virtio_device_restore(&vp_dev->vdev);
> > > }
> > >
> > > +static bool vp_supports_pm_no_reset(struct device *dev)
> > > +{
> > > + struct pci_dev *pci_dev = to_pci_dev(dev);
> > > + u16 pmcsr;
> > > +
> > > + if (!pci_dev->pm_cap)
> > > + return false;
> > > +
> > > + pci_read_config_word(pci_dev, pci_dev->pm_cap + PCI_PM_CTRL, &pmcsr);
> > > + if (PCI_POSSIBLE_ERROR(pmcsr)) {
> > > + dev_err(dev, "Unable to query pmcsr");
> > > + return false;
> > > + }
> > > +
> > > + return pmcsr & PCI_PM_CTRL_NO_SOFT_RESET;
> > > +}
> > > +
> > > +static int virtio_pci_suspend(struct device *dev)
> > > +{
> > > + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_freeze(dev);
> > > +}
> > > +
> > > +static int virtio_pci_resume(struct device *dev)
> > > +{
> > > + return vp_supports_pm_no_reset(dev) ? 0 : virtio_pci_restore(dev);
> > > +}
> > > +
> > > static const struct dev_pm_ops virtio_pci_pm_ops = {
> > > - SET_SYSTEM_SLEEP_PM_OPS(virtio_pci_freeze, virtio_pci_restore)
> > > + .suspend = virtio_pci_suspend,
> > > + .resume = virtio_pci_resume,
> > > + .freeze = virtio_pci_freeze,
> > > + .thaw = virtio_pci_restore,
> > > + .poweroff = virtio_pci_freeze,
> > > + .restore = virtio_pci_restore,
> > > };
> > > #endif
> > >
> > > --
> > > 2.43.0.472.g3155946c3a-goog
> >
