Re: Patch "PCI/sysfs: Ensure devices are powered for config reads" has been added to the 6.6-stable tree

[Brian Norris <briannorris@chromium.org>]

Hi Greg,

On Fri, Oct 17, 2025 at 08:58:20AM +0200, Greg Kroah-Hartman wrote:
> On Thu, Oct 16, 2025 at 08:15:46AM -0700, Brian Norris wrote:
> > Hi,
> > 
> > On Thu, Oct 16, 2025 at 03:09:27PM +0200, Greg Kroah-Hartman wrote:
> > > 
> > > This is a note to let you know that I've just added the patch titled
> > > 
> > >     PCI/sysfs: Ensure devices are powered for config reads
> > > 
> > > to the 6.6-stable tree which can be found at:
> > >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > > 
> > > The filename of the patch is:
> > >      pci-sysfs-ensure-devices-are-powered-for-config-reads.patch
> > > and it can be found in the queue-6.6 subdirectory.
> > > 
> > > If you, or anyone else, feels it should not be added to the stable tree,
> > > please let <stable@vger.kernel.org> know about it.
> > 
> > Adding to the stable tree is good IMO, but one note about exactly how to
> > do so below:
> > 
> > > Wrap these access in pci_config_pm_runtime_{get,put}() like most of the
> > > rest of the similar sysfs attributes.
> > > 
> > > Notably, "max_link_speed" does not access config registers; it returns a
> > > cached value since d2bd39c0456b ("PCI: Store all PCIe Supported Link
> > > Speeds").
> > 
> > ^^ This note about commit d2bd39c0456b was specifically to provide hints
> > about backporting. Without commit d2bd39c0456b, the solution is somewhat
> > incomplete. We should either backport commit d2bd39c0456b as well, or we
> > should adapt the change to add pci_config_pm_runtime_{get,put}() in
> > max_link_speed_show() too.
> 
> I missed that "hint", you need to make it bindingly obvious as I churn
> through the giant "-rc1 merge dump" very quickly as obviously those are
> changes that were not serious enough to make it into -final :)

Oh, no, I didn't mean to imply you "missed" anything. It was more of a
self-help comment, so I could refer to it when following up here.
Otherwise, I also might not trivially remember which commit was
involved. And I didn't know at the time how many branches would contain
commit d2bd39c0456b.

Sorry if my wording was a bit off.

> > Commit d2bd39c0456b was already ported to 6.12.y, but seemingly no
> > further.
> > 
> > If adapting this change to pre-commit-d2bd39c0456b is better, I can
> > submit an updated version here.
> > 
> > Without commit d2bd39c0456b, it just means that the 'max_link_speed'
> > sysfs attribute is still susceptible to accessing a powered-down
> > device/link. We're in no worse state than we were without this patch.
> > And frankly, people are not likely to notice if they haven't already,
> > since I'd guess most systems don't suspend devices this aggressively.
> 
> I'll gladly accept a fixed up patch for this, thanks.

I'll try to get that out today.

Brian