linux-kernel - Re: [PATCH 1/1] vfio-pci: Add SR-IOV VF configuration via sysfs

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Message-ID: <1412172233.7360.203.camel@ul30vt.home>
Date:	Wed, 01 Oct 2014 08:03:53 -0600
From:	Alex Williamson <alex.williamson@...hat.com>
To:	Andre Richter <andre.o.richter@...il.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] vfio-pci: Add SR-IOV VF configuration via sysfs

On Wed, 2014-10-01 at 15:38 +0200, Andre Richter wrote:
> If a PCIe device bound to vfio-pci happens to be SR-IOV capabale,
> there is no possibility to bring up/shutdown the device's VFs.
> 
> This patch adds a generic callback for the sysfs sriov_numvfs attribute.
> The attribute will only show up for SR-IOV devices. Additionally,
> each utilized pci_* function checks if the device is a PF.
> 
> Signed-off-by: Andre Richter <andre.o.richter@...il.com>
> ---
>  drivers/vfio/pci/vfio_pci.c | 25 ++++++++++++++++++++-----
>  1 file changed, 20 insertions(+), 5 deletions(-)

I don't understand why you'd want to do this.  The PF is typically
managed by a host driver.  By allowing vfio-pci to manage SR-IOV, don't
we potentially have assign-able PFs managing assign-able VFs?  That
seems like a bad idea.  What use case do you have in mind?  Thanks,

Alex

> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index f782533..2f6dfb3 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -919,12 +919,27 @@ static struct pci_error_handlers vfio_err_handlers = {
>  	.error_detected = vfio_pci_aer_err_detected,
>  };
>  
> +static int vfio_pci_sriov_configure(struct pci_dev *pdev, int num_vfs)
> +{
> +	int ret = 0;
> +
> +	if (num_vfs > 0) {
> +		ret = pci_enable_sriov(pdev, num_vfs);
> +		if (!ret)
> +			ret = pci_num_vf(pdev);
> +	} else
> +		pci_disable_sriov(pdev);
> +
> +	return ret;
> +}
> +
>  static struct pci_driver vfio_pci_driver = {
> -	.name		= "vfio-pci",
> -	.id_table	= NULL, /* only dynamic ids */
> -	.probe		= vfio_pci_probe,
> -	.remove		= vfio_pci_remove,
> -	.err_handler	= &vfio_err_handlers,
> +	.name			= "vfio-pci",
> +	.id_table		= NULL, /* only dynamic ids */
> +	.probe			= vfio_pci_probe,
> +	.remove			= vfio_pci_remove,
> +	.sriov_configure	= vfio_pci_sriov_configure,
> +	.err_handler		= &vfio_err_handlers,
>  };
>  
>  /*



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