Re: [virtio-dev] Re: [PATCH v3] virtio_pci: support enabling VFs

From: Michael S. Tsirkin
Date: Wed Jun 06 2018 - 08:44:19 EST

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On Wed, Jun 06, 2018 at 08:11:54PM +0800, Tiwei Bie wrote:
> On Tue, Jun 05, 2018 at 03:23:11PM +0300, Michael S. Tsirkin wrote:
> > On Tue, Jun 05, 2018 at 09:36:53AM +0800, Tiwei Bie wrote:
> > > On Mon, Jun 04, 2018 at 07:32:25PM +0300, Michael S. Tsirkin wrote:
> > > > On Fri, Jun 01, 2018 at 12:02:39PM +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@xxxxxxxxx>
> > > > > ---
> > > >
> > > > OK but what about freeze/restore functions?
> >
> > So for restore, don't you need to restore the
> > sriov capability?
>
> Currently I'm not familiar with the PM part.
> But I still think the sriov capability should
> be handled by PCI core.

OK but the point is restore looks just like power up for device.

> I'm trying to understand
> all the relevant code..
> For your question, based on what I found from
> the code currently, I guess the sriov capability
> will be restored by pci_restore_state() which
> will be called by the ops in pci_dev_pm_ops.
> The sriov_restore_state() will be called
> eventually.
>
> Best regards,
> Tiwei Bie

Right but my point is during resume SRIOV gets enabled first before
driver ok.

Maybe we should relax the requirements in the spec:
- only require FEATURES_OK from device, not DRIVER_OK from driver
- explain that it only has to happen once, not on each reset,
and driver can remember the result

>
> >
> >
> > > > I also wonder about kexec - virtio.c currently does:
> > > >
> > > > /* We always start by resetting the device, in case a previous
> > > > * driver messed it up. This also tests that code path a little. */
> > > > dev->config->reset(dev);
> > > >
> > > > Do we need to do something like this for sriov?
> > >
> > > I think VFs are managed by PCI core. Once they are
> > > allocated, virtio driver doesn't have to care too
> > > much about how to manage them. The proposal for the
> > > spec is just to provide a feature bit based virtio
> > > way for virtio drivers to know whether a virtio
> > > device is SR-IOV capable (and virtio drivers can
> > > support configuring SR-IOV based on the feature
> > > bit negotiation result).
> > >
> > > >
> > > > I also wonder whether PCI core should disable sriov for us.
> > > >
> > > >
> > > > I wish there was a patch emulating this without vDPA for QEMU,
> > > > would make it easy to test your patches. Do you happen
> > > > to have something like this?
> > >
> > > Sorry, currently I don't have anything like this..
> > >
> > > Best regards,
> > > Tiwei Bie
> > >
> > > >
> > > > Thanks,
> > > >
> > > >
> > > > > v3:
> > > > > - Drop the acks;
> > > > >
> > > > > v2:
> > > > > - Disable VFs when unbinding the driver (Alex, MST);
> > > > > - Don't use pci_sriov_configure_simple (Alex);
> > > > >
> > > > > drivers/virtio/virtio_pci_common.c | 30 ++++++++++++++++++++++++++++++
> > > > > drivers/virtio/virtio_pci_modern.c | 14 ++++++++++++++
> > > > > include/uapi/linux/virtio_config.h | 7 ++++++-
> > > > > 3 files changed, 50 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> > > > > index 48d4d1cf1cb6..1d4467b2dc31 100644
> > > > > --- a/drivers/virtio/virtio_pci_common.c
> > > > > +++ b/drivers/virtio/virtio_pci_common.c
> > > > > @@ -577,6 +577,8 @@ static void virtio_pci_remove(struct pci_dev *pci_dev)
> > > > > struct virtio_pci_device *vp_dev = pci_get_drvdata(pci_dev);
> > > > > struct device *dev = get_device(&vp_dev->vdev.dev);
> > > > >
> > > > > + pci_disable_sriov(pci_dev);
> > > > > +
> > > > > unregister_virtio_device(&vp_dev->vdev);
> > > > >
> > > > > if (vp_dev->ioaddr)
> > > > > @@ -588,6 +590,33 @@ 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 ret;
> > > > > +
> > > > > + if (!(vdev->config->get_status(vdev) & VIRTIO_CONFIG_S_DRIVER_OK))
> > > > > + return -EBUSY;
> > > > > +
> > > > > + if (!__virtio_test_bit(vdev, VIRTIO_F_SR_IOV))
> > > > > + return -EINVAL;
> > > > > +
> > > > > + if (pci_vfs_assigned(pci_dev))
> > > > > + return -EPERM;
> > > > > +
> > > > > + if (num_vfs == 0) {
> > > > > + pci_disable_sriov(pci_dev);
> > > > > + return 0;
> > > > > + }
> > > > > +
> > > > > + ret = pci_enable_sriov(pci_dev, num_vfs);
> > > > > + if (ret < 0)
> > > > > + return ret;
> > > > > +
> > > > > + return num_vfs;
> > > > > +}
> > > > > +
> > > > > static struct pci_driver virtio_pci_driver = {
> > > > > .name = "virtio-pci",
> > > > > .id_table = virtio_pci_id_table,
> > > > > @@ -596,6 +625,7 @@ 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
> > > >
> > > > ---------------------------------------------------------------------
> > > > To unsubscribe, e-mail: virtio-dev-unsubscribe@xxxxxxxxxxxxxxxxxxxx
> > > > For additional commands, e-mail: virtio-dev-help@xxxxxxxxxxxxxxxxxxxx
> > > >

Next message: Rafael J. Wysocki: "Re: [4.17 regression] Performance drop on kernel-4.17 visible on Stream, Linpack and NAS parallel benchmarks"
Previous message: Julia Lawall: "Re: unnecessary test?"
In reply to: Tiwei Bie: "Re: [virtio-dev] Re: [PATCH v3] virtio_pci: support enabling VFs"
Next in thread: Tiwei Bie: "Re: [virtio-dev] Re: [PATCH v3] virtio_pci: support enabling VFs"
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