From: Tom Lyon <pugs@cisco.com>
Organization: Cisco Systems, Inc.
To: Alex Williamson <alex.williamson@redhat.com>
Subject: Re: [PATCH] vfio: Fix PCI 2.3 shared interrupt
Date: Wed, 3 Nov 2010 14:03:52 -0700
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        kvm@vger.kernel.org
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Applied.

On Wednesday, November 03, 2010 01:17:33 pm Alex Williamson wrote:
> Trying to be too clever with setting the irq_disabled flag.  PCI 2.3
> disabled devices can still share IRQs, which can lead to clearing
> the irq_disabled flag, preventing the EOI from registering, and leaving
> the device without interrupts.  Interrupt handler should only ever
> set irq_disabled and we can exit earlier to avoid the config space
> access if we know we're disabled.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
> 
>  drivers/vfio/vfio_intrs.c |    9 ++++++++-
>  1 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/vfio/vfio_intrs.c b/drivers/vfio/vfio_intrs.c
> index 604082c..73e3deb 100644
> --- a/drivers/vfio/vfio_intrs.c
> +++ b/drivers/vfio/vfio_intrs.c
> @@ -57,6 +57,12 @@ irqreturn_t vfio_interrupt(int irq, void *dev_id)
> 
>  	spin_lock_irq(&vdev->irqlock);
> 
> +	/* INTX disabled interrupts can still be shared */
> +	if (vdev->irq_disabled) {
> +		spin_unlock_irq(&vdev->irqlock);
> +		return ret;
> +	}
> +
>  	if (vdev->pci_2_3) {
>  		pci_block_user_cfg_access(pdev);
> 
> @@ -87,7 +93,8 @@ done:
>  		ret = IRQ_HANDLED;
>  	}
> 
> -	vdev->irq_disabled = (ret == IRQ_HANDLED);
> +	if (ret == IRQ_HANDLED)
> +		vdev->irq_disabled = true;
> 
>  	spin_unlock_irq(&vdev->irqlock);
--
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