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

Fam Zheng
2015-03-13T02:09:29Z

On Thu, 03/12 19:56, Bandan Das wrote:
> Hi Fam,
>
> Fam Zheng <famz@redhat.com> writes:
>
> > 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);
> > + }
>
> If the driver doesn't provide a shutdown method and doesn't itself
> disable MSI/MSI-X, then pci_msi(x)_shutdown won't be called anymore,
> no ?

Right.

>
> This is probably ok (but unclean) for a system shutdown, but could
> cause problems for something like kexec ?

Doesn't the reset in kexec clean this up during initialization?

Without shutdown, anything in the driver is unclean anyway, for example
free_irq is not called.

Fam