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

Paolo Bonzini
2015-03-12T16:21:39Z

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.

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

Paolo