linux-kernel - Re: [Xen-devel] [PATCH 1/4] xen/pciback: Check PF instead of VF for PCI_COMMAND

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Date:	Fri, 12 Feb 2016 02:19:34 -0700
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Konrad Rzeszutek Wilk" <konrad.wilk@...cle.com>
Cc:	"Tommi Airikka" <tommi@...ikka.net>, <david.vrabel@...rix.com>,
	<xen-devel@...ts.xenproject.org>, <boris.ostrovsky@...cle.com>,
	<linux-kernel@...r.kernel.org>, <stable@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH 1/4] xen/pciback: Check PF instead of
 VF for PCI_COMMAND_MEMORY

>>> On 11.02.16 at 22:10, <konrad.wilk@...cle.com> wrote:
> c/s 408fb0e5aa7fda0059db282ff58c3b2a4278baa0
> "xen/pciback: Don't allow MSI-X ops if PCI_COMMAND_MEMORY is not set."
> would check the device for PCI_COMMAND_MEMORY which is great.
> Except that VF devices are unique - for example they have no
> legacy interrupts, and also any writes to PCI_COMMAND_MEMORY
> are silently ignored (by the hardware).
> 
> CC: stable@...r.kernel.org 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Reviewed-by: Jan Beulich <jbeulich@...e.com>

albeit ...

> --- a/drivers/xen/xen-pciback/pciback_ops.c
> +++ b/drivers/xen/xen-pciback/pciback_ops.c
> @@ -213,6 +213,7 @@ int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
>  	int i, result;
>  	struct msix_entry *entries;
>  	u16 cmd;
> +	struct pci_dev *phys_dev;
>  
>  	if (unlikely(verbose_request))
>  		printk(KERN_DEBUG DRV_NAME ": %s: enable MSI-X\n",
> @@ -227,8 +228,10 @@ int xen_pcibk_enable_msix(struct xen_pcibk_device *pdev,
>  	/*
>  	 * PCI_COMMAND_MEMORY must be enabled, otherwise we may not be able
>  	 * to access the BARs where the MSI-X entries reside.
> +	 * But VF devices are unique in which the PF needs to be checked.
>  	 */
> -	pci_read_config_word(dev, PCI_COMMAND, &cmd);
> +	phys_dev = pci_physfn(dev);
> +	pci_read_config_word(phys_dev, PCI_COMMAND, &cmd);

... I don't think the use of a local variable here is really needed.

Jan