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

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Date:	Fri, 13 Mar 2015 10:09:19 +0800
From:	Fam Zheng <famz@...hat.com>
To:	Bandan Das <bsd@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	linux-pci@...r.kernel.org
Subject: Re: [RFC PATCH] PCI: Disable MSI/MSI-X only if device is shutdown

On Thu, 03/12 19:56, Bandan Das wrote:
> Hi Fam,
> 
> Fam Zheng <famz@...hat.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@...hat.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
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