On Fri, 2021-05-07 at 23:25 -0400, Sasha Levin wrote: > This is a note to let you know that I've just added the patch titled > > s390/pci: expose UID uniqueness guarantee > > to the 5.12-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: > s390-pci-expose-uid-uniqueness-guarantee.patch > and it can be found in the queue-5.12 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. > > > > commit 7b9825aa0891087c5c91be0fb75431919e2027e3 > Author: Niklas Schnelle <schnelle@xxxxxxxxxxxxx> > Date: Wed Feb 24 11:29:36 2021 +0100 > > s390/pci: expose UID uniqueness guarantee > > [ Upstream commit 408f2c9c15682fc21b645fdec1f726492e235c4b ] > > On s390 each PCI device has a user-defined ID (UID) exposed under > /sys/bus/pci/devices/<dev>/uid. This ID was designed to serve as the PCI > device's primary index and to match the device within Linux to the > device configured in the hypervisor. To serve as a primary identifier > the UID must be unique within the Linux instance, this is guaranteed by > the platform if and only if the UID Uniqueness Checking flag is set > within the CLP List PCI Functions response. > > While the UID has been exposed to userspace since commit ac4995b9d570 > ("s390/pci: add some new arch specific pci attributes") whether or not > the platform guarantees its uniqueness for the lifetime of the Linux > instance while defined is not visible from userspace. Remedy this by > exposing this as a per device attribute at > > /sys/bus/pci/devices/<dev>/uid_is_unique > > Keeping this a per device attribute allows for maximum flexibility if we > ever end up with some devices not having a UID or not enjoying the > guaranteed uniqueness. > > Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx> > Reviewed-by: Viktor Mihajlovski <mihajlov@xxxxxxxxxxxxx> > Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > > Hi Sasha, I think we should not backport this patch to the stable kernels either 5.12, 5.11 nor 5.10. The reason is that I'd like this staty together with commit 81bbf03905aa ("s390/pci: expose a PCI device's UID as its index") since this then allows to reason that if uid_is_unique is 1 that implies that the index attribute must exist. On the other hand backporting the other patch too would create new network interface names. I reckon that there would be some value for the uid_is_unique attribute alone but I think it's not worth having more possible scenarios. Thanks, Niklas Schnelle
