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Date: Wed, 13 Jan 2021 21:49:18 +0200 From: Leon Romanovsky <leon@...nel.org> To: Alex Williamson <alex.williamson@...hat.com> Cc: Bjorn Helgaas <bhelgaas@...gle.com>, Saeed Mahameed <saeedm@...dia.com>, Jason Gunthorpe <jgg@...dia.com>, Jakub Kicinski <kuba@...nel.org>, linux-pci@...r.kernel.org, linux-rdma@...r.kernel.org, netdev@...r.kernel.org, Don Dutile <ddutile@...hat.com> Subject: Re: [PATCH mlx5-next v1 1/5] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs 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@...nel.org> wrote: > > > From: Leon Romanovsky <leonro@...dia.com> > > > > 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@...dia.com> > > --- > > 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
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