Re: [RFC PATCH V4] pci: virtio_pci: Add SR-IOV support for virtio_pci devices

[Alexander Duyck]

On Sun, Feb 25, 2018 at 8:48 PM, Mark Rustad <mark.d.rustad@xxxxxxxxx> wrote:
> 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 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.
>
> Signed-off-by: Mark Rustad <mark.d.rustad@xxxxxxxxx>
> Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxx>

Mark,

In the future please don't put my "Reviewed-by" on a patch that I
haven't reviewed. I believe I reviewed one of the earlier patches, but
I hadn't reviewed this version.

Also, after thinking about it over the weekend we may want to look at
just coming up with a truly "generic" solution that is applied to
SR-IOV capable devices that don't have a SR-IOV capable driver loaded
on them. That would allow us to handle the uio, vfio, pci-stub, and
virtio cases all in one fell swoop. I think us going though and
modifying one patch at a time to do this kind of thing isn't going to
scale.

I'll try to do some digging and find the VFIO approach we had been
working on. I think with a couple tweaks we can probably make that
truly generic and ready for submission.

Thanks.

- Alex

> ---
> Changes in V4:
> - V3 was a mis-send, this has what was intended
> - Move most code to new helpers in pci/iov.c, pci_sriov_configure_generic
>   and pci_sriov_disable_generic
> - Correct mislabeling of vendor and device IDs
> - Other minor changelog fixes
> - Rebased to pci/master, since most changes are in that area now
> - No new ifdefs with this approach (yay)
> Changes in V3:
> - Missent patch, please disregard
> Changes in V2:
> - Simplified logic from previous version, removed added driver variable
> - Disable SR-IOV on driver removal except when VFs are assigned
> - Sent as RFC to virtio-dev, linux-pci, netdev, lkml and others
> ---
>  drivers/pci/iov.c                  |   50 ++++++++++++++++++++++++++++++++++++
>  drivers/virtio/virtio_pci_common.c |    2 +
>  include/linux/pci.h                |   10 +++++++
>  3 files changed, 62 insertions(+)
>
> diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> index 677924ae0350..4b110e169b7c 100644
> --- a/drivers/pci/iov.c
> +++ b/drivers/pci/iov.c
> @@ -367,6 +367,56 @@ static void sriov_disable(struct pci_dev *dev)
>         pci_iov_set_numvfs(dev, 0);
>  }
>
> +/**
> + * pci_sriov_disable_generic - standard helper to disable SR-IOV
> + * @dev:the PCI PF device whose VFs are to be disabled
> + */
> +int pci_sriov_disable_generic(struct pci_dev *dev)
> +{
> +       /*
> +        * If vfs are assigned we cannot shut down SR-IOV without causing
> +        * issues, so just leave the hardware available.
> +        */
> +       if (pci_vfs_assigned(dev)) {
> +               pci_warn(dev,
> +                        "Cannot disable SR-IOV while VFs are assigned - VFs will not be deallocated\n");
> +               return -EPERM;
> +       }
> +       pci_disable_sriov(dev);
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(pci_sriov_disable_generic);
> +
> +static int pci_sriov_enable(struct pci_dev *dev, int num_vfs)
> +{
> +       int rc;
> +
> +       if (pci_num_vf(dev))
> +               return -EINVAL;
> +
> +       rc = pci_enable_sriov(dev, num_vfs);
> +       if (rc) {
> +               pci_warn(dev, "Failed to enable PCI sriov: %d\n", rc);
> +               return rc;
> +       }
> +       pci_info(dev, "SR-IOV enabled with %d VFs\n", num_vfs);
> +       return num_vfs;
> +}
> +
> +/**
> + * pci_sriov_configure_generic - standard helper to configure SR-IOV
> + * @dev: the PCI PF device that is configuring SR-IOV
> + */
> +int pci_sriov_configure_generic(struct pci_dev *dev, int num_vfs)
> +{
> +       if (num_vfs)
> +               return pci_sriov_enable(dev, num_vfs);
> +       if (!pci_num_vf(dev))
> +               return -EINVAL;
> +       return pci_sriov_disable_generic(dev);
> +}
> +EXPORT_SYMBOL_GPL(pci_sriov_configure_generic);
> +
>  static int sriov_init(struct pci_dev *dev, int pos)
>  {
>         int i, bar64;
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 48d4d1cf1cb6..d7679377131f 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -584,6 +584,7 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
>         else
>                 virtio_pci_modern_remove(vp_dev);
>
> +       pci_sriov_disable_generic(pci_dev);
>         pci_disable_device(pci_dev);
>         put_device(dev);
>  }
> @@ -596,6 +597,7 @@ static struct pci_driver virtio_pci_driver = {
>  #ifdef CONFIG_PM_SLEEP
>         .driver.pm      = &virtio_pci_pm_ops,
>  #endif
> +       .sriov_configure = pci_sriov_configure_generic,
>  };
>
>  module_pci_driver(virtio_pci_driver);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 024a1beda008..937124d4e098 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1947,6 +1947,8 @@ int pci_iov_virtfn_devfn(struct pci_dev *dev, int id);
>
>  int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
>  void pci_disable_sriov(struct pci_dev *dev);
> +int pci_sriov_disable_generic(struct pci_dev *dev);
> +int pci_sriov_configure_generic(struct pci_dev *dev, int num_vfs);
>  int pci_iov_add_virtfn(struct pci_dev *dev, int id);
>  void pci_iov_remove_virtfn(struct pci_dev *dev, int id);
>  int pci_num_vf(struct pci_dev *dev);
> @@ -1973,6 +1975,14 @@ static inline int pci_iov_add_virtfn(struct pci_dev *dev, int id)
>  static inline void pci_iov_remove_virtfn(struct pci_dev *dev,
>                                          int id) { }
>  static inline void pci_disable_sriov(struct pci_dev *dev) { }
> +static inline int pci_sriov_disable_generic(struct pci_dev *dev)
> +{
> +       return -ENODEV;
> +}
> +static inline int pci_sriov_configure_generic(struct pci_dev *dev, int num_vfs)
> +{
> +       return -ENODEV;
> +}
>  static inline int pci_num_vf(struct pci_dev *dev) { return 0; }
>  static inline int pci_vfs_assigned(struct pci_dev *dev)
>  { return 0; }
>