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

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Date:	Thu, 12 Mar 2015 19:56:21 -0400
From:	Bandan Das <bsd@...hat.com>
To:	Fam Zheng <famz@...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

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 ?

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

Bandan

>  #ifdef CONFIG_KEXEC
>  	/*
--
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