linux-kernel - Re: [virtio-dev] [pci PATCH v7 2/5] virtio_pci: Add support for unmanaged SR-IOV on virtio

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Date:   Tue, 3 Apr 2018 16:11:33 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     bhelgaas@...gle.com, alexander.h.duyck@...el.com,
        linux-pci@...r.kernel.org, virtio-dev@...ts.oasis-open.org,
        kvm@...r.kernel.org, netdev@...r.kernel.org, dan.daly@...el.com,
        linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        keith.busch@...el.com, netanel@...zon.com, ddutile@...hat.com,
        mheyne@...zon.de, liang-min.wang@...el.com,
        mark.d.rustad@...el.com, dwmw2@...radead.org, hch@....de,
        dwmw@...zon.co.uk
Subject: Re: [virtio-dev] [pci PATCH v7 2/5] virtio_pci: Add support for
 unmanaged SR-IOV on virtio_pci devices

On Thu, Mar 15, 2018 at 11:42:41AM -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@...el.com>
> 
> Hardware-realized virtio_pci devices can implement SR-IOV, so this
> patch enables its use. The device in question is an upcoming Intel
> NIC that implements both a virtio_net PF and virtio_net VFs. These
> are hardware realizations of what has been up to now been a software
> interface.
> 
> The device in question has the following 4-part PCI IDs:
> 
> PF: vendor: 1af4 device: 1041 subvendor: 8086 subdevice: 15fe
> VF: vendor: 1af4 device: 1041 subvendor: 8086 subdevice: 05fe
> 
> The patch currently needs no check for device ID, because the callback
> will never be made for devices that do not assert the capability or
> when run on a platform incapable of SR-IOV.
> 
> One reason for this patch is because the hardware requires the
> vendor ID of a VF to be the same as the vendor ID of the PF that
> created it. So it seemed logical to simply have a fully-functioning
> virtio_net PF create the VFs. This patch makes that possible.
> 
> Reviewed-by: Christoph Hellwig <hch@....de>
> Signed-off-by: Mark Rustad <mark.d.rustad@...el.com>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>

I thought hard about this, and I think we need a feature
bit for this. This way host can detect support,
and we can also change our minds later if we need
to modify the interface and manage VFs after all.

It seems PCI specific so non pci transports would disable the feature
for now.

> ---
> 
> v4: Dropped call to pci_disable_sriov in virtio_pci_remove function
> v5: Replaced call to pci_sriov_configure_unmanaged with
>         pci_sriov_configure_simple
> v6: Dropped "#ifdef" checks for IOV wrapping sriov_configure definition
> v7: No code change, added Reviewed-by
> 
>  drivers/virtio/virtio_pci_common.c |    1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 48d4d1cf1cb6..67a227fd7aa0 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -596,6 +596,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
>  #ifdef CONFIG_PM_SLEEP
>  	.driver.pm	= &virtio_pci_pm_ops,
>  #endif
> +	.sriov_configure = pci_sriov_configure_simple,
>  };
>  
>  module_pci_driver(virtio_pci_driver);
> 
> 
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