Re: [RFC PATCH] PCI: Disable MSI/MSI-X only if device is shutdown

Fam Zheng
2015-03-12T23:21:14Z

On Thu, 03/12 17:21, Paolo Bonzini wrote:
> On 12/03/2015 06:21, Fam Zheng wrote:
> > If the device doesn't support shutdown, disabling interrupts may cause
> > trouble. For example, virtio-scsi-pci doesn't implement shutdown, and
> > after we disable MSI-X, futher notifications from device will be
> > delivered to IRQ, which is unexpected. This IRQ will not be cleared, and
> > may prevent us from making progress, by keep triggering interrupts.
> >
> > Signed-off-by: Fam Zheng <famz@redhat.com>
> > ---
> > drivers/pci/pci-driver.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> > index 3cb2210..fb29c96 100644
> > --- a/drivers/pci/pci-driver.c
> > +++ b/drivers/pci/pci-driver.c
> > @@ -448,10 +448,11 @@ static void pci_device_shutdown(struct device *dev)
> >
> > pm_runtime_resume(dev);
> >
> > - if (drv && drv->shutdown)
> > + if (drv && drv->shutdown) {
> > drv->shutdown(pci_dev);
> > - pci_msi_shutdown(pci_dev);
> > - pci_msix_shutdown(pci_dev);
> > + pci_msi_shutdown(pci_dev);
> > + pci_msix_shutdown(pci_dev);
> > + }
> >
> > #ifdef CONFIG_KEXEC
> > /*
> >
>
> The patch may be okay, but I think the bug here is also that virtio-pci
> is not defining a .shutdown callback. It should define one and call
> free_irq (for INTX) and pci_disable_msix.

It's not enough. The device has to know we disabled msix, otherwise it will
send us IRQ, which is wrong.

>
> How is this related to the virtio-scsi patch that you posted? Do you
> need both to fix the problem you reported?
>

This one should be enough. I was wrong in saying virtio-scsi hanging the
shutdown is because requests not being completed, it's more because of the
unexpected IRQ as explained in [1].

[1]: https://bugzilla.redhat.com/attachment.cgi?id=998391

Fam