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

From: Michael S. Tsirkin
Date: Fri Mar 16 2018 - 12:35:02 EST


On Thu, Mar 15, 2018 at 11:42:41AM -0700, Alexander Duyck wrote:
> From: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>
>
> 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@xxxxxx>
> Signed-off-by: Mark Rustad <mark.d.rustad@xxxxxxxxx>
> Signed-off-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>

So if and when virtio PFs can manage the VFs, then we can
add a feature bit for that?
Seems reasonable.

Also, I am guessing that hardware implementations will want
to add things like stong memory barriers - I guess we
will add new feature bits for that too down the road?


> ---
>
> 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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