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    SubjectRe: [RFC PATCH] PCI: Disable MSI/MSI-X only if device is shutdown
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    Ccing Alex, he can probably confirm if my understanding is indeed correct.

    Fam Zheng <famz@redhat.com> writes:

    > 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?

    I guess it would take the same path as a reboot.

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

    True, And that is why the MSI/-X shutdown functions are called here
    because pci can't always rely on the individual device drivers to do
    the right thing, but atleast can make a best effort at cleaning up.

    > Fam


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