On Fri, Mar 29, 2019 at 09:00:58AM +0100, Pierre Crégut wrote: > Ensure that iov->num_VFs is set before a netlink message is sent > when the number of VFs is changed. Only the path for num_VFs > 0 > is affected. The path for num_VFs = 0 is already correct. > > Monitoring programs can relie on netlink messages to track interface > change and query their state in /sys. But when sriov_numvfs is set to a > positive value, the netlink message is sent before the value is available > in sysfs. The value read after the message is received is always zero.
Thanks, Pierre! Can you clue me in on where exactly the connection from sriov_enable() to netlink is? I see one side of the race is with sriov_numvfs_show(), but I don't know where the netlink message is sent. Is that connected with the kobject_uevent(KOBJ_CHANGE)? One thing this would help with is figuring out exactly how *much* earlier we need to set iov->num_VFs. It looks like the current patch sets it before we actually enable the VFs, so a user could read /sys/.../sriov_numvfs and get the wrong value. Of course, that's unavoidable; the question is whether it's OK to get the new value *before* it actually takes effect, or whether we want to return a stale value until after it takes effect. > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991 > Signed-off-by: Pierre Crégut <pierre.cre...@orange.com> > --- > note: the behaviour can be tested with the following shell script also > available on the bugzilla (d being the phy device name): > > ip monitor dev $d | grep --line-buffered "^[0-9]*:" | \ > while read line; do cat /sys/class/net/$d/device/sriov_numvfs; done > > drivers/pci/iov.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index 3aa115ed3a65..a9655c10e87f 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -351,6 +351,7 @@ static int sriov_enable(struct pci_dev *dev, int > nr_virtfn) > goto err_pcibios; > } > > + iov->num_VFs = nr_virtfn; > pci_iov_set_numvfs(dev, nr_virtfn); > iov->ctrl |= PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE; > pci_cfg_access_lock(dev); > @@ -363,7 +364,6 @@ static int sriov_enable(struct pci_dev *dev, int > nr_virtfn) > goto err_pcibios; > > kobject_uevent(&dev->dev.kobj, KOBJ_CHANGE); > - iov->num_VFs = nr_virtfn; > > return 0; > > @@ -379,6 +379,7 @@ static int sriov_enable(struct pci_dev *dev, int > nr_virtfn) > if (iov->link != dev->devfn) > sysfs_remove_link(&dev->dev.kobj, "dep_link"); > > + iov->num_VFs = 0; > pci_iov_set_numvfs(dev, 0); > return rc; > } > -- > 2.17.1 >
