Re: [PATCH] virtio_pci: support enabling VFs

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, May 30, 2018 at 04:55:21PM +0800, Tiwei Bie wrote:
> There is a new feature bit allocated in virtio spec to
> support SR-IOV (Single Root I/O Virtualization):
> 
> https://github.com/oasis-tcs/virtio-spec/issues/11
> 
> This patch enables the support for this feature bit in
> virtio driver.
> 
> Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> ---
> This patch depends on below proposal:
> https://lists.oasis-open.org/archives/virtio-dev/201805/msg00154.html
> 
> This patch depends on below patch:
> https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/virtualization&id=8effc395c2097e258fcedfc02ed4a66d45fb4238
> 
>  drivers/virtio/virtio_pci_common.c | 20 ++++++++++++++++++++
>  drivers/virtio/virtio_pci_modern.c | 14 ++++++++++++++
>  include/uapi/linux/virtio_config.h |  7 ++++++-
>  3 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index 48d4d1cf1cb6..023da80a7a3e 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -588,6 +588,25 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
>  	put_device(dev);
>  }
>  
> +static int virtio_pci_sriov_configure(struct pci_dev *pci_dev, int num_vfs)
> +{
> +	struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
> +	struct virtio_device *vdev = &vp_dev->vdev;
> +	int (*sriov_configure)(struct pci_dev *pci_dev, int num_vfs);
> +
> +	if (!(vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_DRIVER_OK))
> +		return -EBUSY;
> +
> +	if (!__virtio_test_bit(vdev, VIRTIO_F_SR_IOV))
> +		return -EINVAL;
> +
> +	sriov_configure = pci_sriov_configure_simple;
> +	if (sriov_configure == NULL)
> +		return -ENOENT;

BTW what is all this trickery in aid of?

> +
> +	return sriov_configure(pci_dev, num_vfs);
> +}
> +
>  static struct pci_driver virtio_pci_driver = {
>  	.name		= "virtio-pci",
>  	.id_table	= virtio_pci_id_table,
> @@ -596,6 +615,7 @@ static struct pci_driver virtio_pci_driver = {
>  #ifdef CONFIG_PM_SLEEP
>  	.driver.pm	= &virtio_pci_pm_ops,
>  #endif
> +	.sriov_configure = virtio_pci_sriov_configure,
>  };
>  
>  module_pci_driver(virtio_pci_driver);
> diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
> index 2555d80f6eec..07571daccfec 100644
> --- a/drivers/virtio/virtio_pci_modern.c
> +++ b/drivers/virtio/virtio_pci_modern.c
> @@ -153,14 +153,28 @@ static u64 vp_get_features(struct virtio_device *vdev)
>  	return features;
>  }
>  
> +static void vp_transport_features(struct virtio_device *vdev, u64 features)
> +{
> +	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> +	struct pci_dev *pci_dev = vp_dev->pci_dev;
> +
> +	if ((features & BIT_ULL(VIRTIO_F_SR_IOV)) &&
> +			pci_find_ext_capability(pci_dev, PCI_EXT_CAP_ID_SRIOV))
> +		__virtio_set_bit(vdev, VIRTIO_F_SR_IOV);
> +}
> +
>  /* virtio config->finalize_features() implementation */
>  static int vp_finalize_features(struct virtio_device *vdev)
>  {
>  	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
> +	u64 features = vdev->features;
>  
>  	/* Give virtio_ring a chance to accept features. */
>  	vring_transport_features(vdev);
>  
> +	/* Give virtio_pci a chance to accept features. */
> +	vp_transport_features(vdev, features);
> +
>  	if (!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
>  		dev_err(&vdev->dev, "virtio: device uses modern interface "
>  			"but does not have VIRTIO_F_VERSION_1\n");
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index 308e2096291f..b7c1f4e7d59e 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -49,7 +49,7 @@
>   * transport being used (eg. virtio_ring), the rest are per-device feature
>   * bits. */
>  #define VIRTIO_TRANSPORT_F_START	28
> -#define VIRTIO_TRANSPORT_F_END		34
> +#define VIRTIO_TRANSPORT_F_END		38
>  
>  #ifndef VIRTIO_CONFIG_NO_LEGACY
>  /* Do we get callbacks when the ring is completely used, even if we've
> @@ -71,4 +71,9 @@
>   * this is for compatibility with legacy systems.
>   */
>  #define VIRTIO_F_IOMMU_PLATFORM		33
> +
> +/*
> + * Does the device support Single Root I/O Virtualization?
> + */
> +#define VIRTIO_F_SR_IOV			37
>  #endif /* _UAPI_LINUX_VIRTIO_CONFIG_H */
> -- 
> 2.17.0