On Wed, Jan 13, 2021 at 10:50:52AM -0700, Alex Williamson wrote:
> On Sun, 10 Jan 2021 17:07:23 +0200
> Leon Romanovsky <leon@xxxxxxxxxx> wrote:
>
> > From: Leon Romanovsky <leonro@xxxxxxxxxx>
> >
> > Extend PCI sysfs interface with a new callback that allows configure
> > the number of MSI-X vectors for specific SR-IO VF. This is needed
> > to optimize the performance of newly bound devices by allocating
> > the number of vectors based on the administrator knowledge of targeted VM.
> >
> > This function is applicable for SR-IOV VF because such devices allocate
> > their MSI-X table before they will run on the VMs and HW can't guess the
> > right number of vectors, so the HW allocates them statically and equally.
> >
> > The newly added /sys/bus/pci/devices/.../vf_msix_vec file will be seen
> > for the VFs and it is writable as long as a driver is not bounded to the VF.
> >
> > The values accepted are:
> > * > 0 - this will be number reported by the VF's MSI-X capability
> > * < 0 - not valid
> > * = 0 - will reset to the device default value
> >
> > Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxx>
> > ---
> > Documentation/ABI/testing/sysfs-bus-pci | 20 ++++++++
> > drivers/pci/iov.c | 62 +++++++++++++++++++++++++
> > drivers/pci/msi.c | 29 ++++++++++++
> > drivers/pci/pci-sysfs.c | 1 +
> > drivers/pci/pci.h | 2 +
> > include/linux/pci.h | 8 +++-
> > 6 files changed, 121 insertions(+), 1 deletion(-)
<...>
> > +/**
> > + * pci_set_msix_vec_count - change the reported number of MSI-X vectors
> > + * This function is applicable for SR-IOV VF because such devices allocate
> > + * their MSI-X table before they will run on the VMs and HW can't guess the
> > + * right number of vectors, so the HW allocates them statically and equally.
> > + * @dev: VF device that is going to be changed
> > + * @numb: amount of MSI-X vectors
> > + **/
> > +int pci_set_msix_vec_count(struct pci_dev *dev, int numb)
> > +{
> > + struct pci_dev *pdev = pci_physfn(dev);
> > +
> > + if (!dev->msix_cap || !pdev->msix_cap)
> > + return -EINVAL;
> > +
> > + if (dev->driver || !pdev->driver ||
> > + !pdev->driver->sriov_set_msix_vec_count)
> > + return -EOPNOTSUPP;
>
>
> This seems racy, don't we need to hold device_lock on both the VF and
> PF to avoid driver {un}binding races? Does that happen implicitly
> somewhere? Thanks,
Yes, you are right absolutely, pdev and dev are not protected here.
Thanks
