lkml.org 
[lkml]   [2019]   [Oct]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] PCI/IOV: update num_VFs earlier
On Tue, Oct 08, 2019 at 06:06:46PM -0400, Don Dutile wrote:
> On 10/08/2019 05:38 PM, Bjorn Helgaas wrote:
> > On Thu, Oct 03, 2019 at 05:10:07PM -0500, Bjorn Helgaas wrote:
> > > On Thu, Oct 03, 2019 at 11:04:45AM +0200, CREGUT Pierre IMT/OLN wrote:
> > > > ...
> >
> > > > NIC drivers send netlink events when their state change, but it is
> > > > the core that changes the value of num_vfs. So I would think it is
> > > > the core responsibility to make sure the exposed value makes sense
> > > > and it would be better to ignore the details of the driver
> > > > implementation.
> > >
> > > Yes, I think you're right. And I like your previous suggestion of
> > > just locking the device in the reader. I'm not enough of a sysfs
> > > expert to know if there's a good reason to avoid a lock there. Does
> > > the following look reasonable to you?
> >
> > I applied the patch below to pci/virtualization for v5.5, thanks for
> I hope not... see below
>
> > your great patience!
> >
> > > commit 0940fc95da45
> > > Author: Pierre Crégut <pierre.cregut@orange.com>
> > > Date: Wed Sep 11 09:27:36 2019 +0200
> > >
> > > PCI/IOV: Serialize sysfs sriov_numvfs reads vs writes
> > > When sriov_numvfs is being updated, drivers may notify about new devices
> > > before they are reflected in sriov->num_VFs, so concurrent sysfs reads
> > > previously returned stale values.
> > > Serialize the sysfs read vs the write so the read returns the correct
> > > num_VFs value.
> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=202991
> > > Link: https://lore.kernel.org/r/20190911072736.32091-1-pierre.cregut@orange.com
> > > Signed-off-by: Pierre Crégut <pierre.cregut@orange.com>
> > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
> > >
> > > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
> > > index b3f972e8cfed..e77562aabbae 100644
> > > --- a/drivers/pci/iov.c
> > > +++ b/drivers/pci/iov.c
> > > @@ -254,8 +254,14 @@ static ssize_t sriov_numvfs_show(struct device *dev,
> > > char *buf)
> > > {
> > > struct pci_dev *pdev = to_pci_dev(dev);
> > > + u16 num_vfs;
> > > +
> > > + /* Serialize vs sriov_numvfs_store() so readers see valid num_VFs */
> > > + device_lock(&pdev->dev);
> ^^^^^ lock
> > > + num_vfs = pdev->sriov->num_VFs;
> > > + device_lock(&pdev->dev);
> ^^^^ and lock again!

Oops, sorry, my fault. Fixed.

> > > - return sprintf(buf, "%u\n", pdev->sriov->num_VFs);
> > > + return sprintf(buf, "%u\n", num_vfs);
> > > }
> > > /*
>

\
 
 \ /
  Last update: 2019-10-09 14:32    [W:0.047 / U:6.808 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site