linux-kernel - Re: [PATCH] vfio: fix config virtualization, esp command byte

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Date:	Tue, 16 Nov 2010 21:14:50 -0800
From:	Tom Lyon <pugs@...co.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org
Subject: Re: [PATCH] vfio: fix config virtualization, esp command byte

Applied.

On Tuesday, November 16, 2010 10:57:27 am Alex Williamson wrote:
> On Tue, 2010-11-16 at 10:54 -0700, Alex Williamson wrote:
> > On Tue, 2010-11-09 at 17:09 -0800, Tom Lyon wrote:
> > > Cleans up config space virtualization, especialy handling of bytes
> > > which have some virtual and some real bits, like PCI_COMMAND.
> > > 
> > > Alex, I hope you can test this with your setups.
> > 
> > Sorry for the delay.  FWIW, I'm not having much luck with this, I'll try
> > to debug the problem.  Thanks,
> 
> This seems to be the bug.  Thanks,
> 
> Alex
> 
> vfio: Don't write random bits on read
> 
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
> 
> diff --git a/drivers/vfio/vfio_pci_config.c
> b/drivers/vfio/vfio_pci_config.c index 7132ac4..422d7b1 100644
> --- a/drivers/vfio/vfio_pci_config.c
> +++ b/drivers/vfio/vfio_pci_config.c
> @@ -964,11 +964,6 @@ static int vfio_config_rwbyte(int write,
>  		return 0;
>  	}
> 
> -	if (write) {
> -		if (copy_from_user(&newval, buf, 1))
> -			return -EFAULT;
> -	}
> -
>  	if (~virt) {	/* mix of real and virt bits */
>  		/* update vconfig with latest hw bits */
>  		ret = vfio_read_config_byte(vdev, pos, &realbits);
> @@ -978,9 +973,14 @@ static int vfio_config_rwbyte(int write,
>  			(vdev->vconfig[pos] & virt) | (realbits & ~virt);
>  	}
> 
> -	/* update vconfig with writeable bits */
> -	vdev->vconfig[pos] =
> -		(vdev->vconfig[pos] & ~wr) | (newval & wr);
> +	if (write) {
> +		if (copy_from_user(&newval, buf, 1))
> +			return -EFAULT;
> +
> +		/* update vconfig with writeable bits */
> +		vdev->vconfig[pos] =
> +			(vdev->vconfig[pos] & ~wr) | (newval & wr);
> +        }
> 
>  	/*
>  	 * Now massage virtual fields
--
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