From mboxrd@z Thu Jan 1 00:00:00 1970 From: jan.glauber@caviumnetworks.com (Jan Glauber) Date: Tue, 26 Apr 2016 14:08:09 +0200 Subject: [PATCH v2 0/5] Cavium ThunderX uncore PMU support In-Reply-To: <20160425131907.GB30830@arm.com> References: <20160404121954.GA9300@hardcore> <20160425112207.GL16065@arm.com> <20160425120222.GA2552@hardcore> <20160425131907.GB30830@arm.com> Message-ID: <20160426120809.GA9796@hardcore> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Apr 25, 2016 at 02:19:07PM +0100, Will Deacon wrote: > On Mon, Apr 25, 2016 at 02:02:22PM +0200, Jan Glauber wrote: > > On Mon, Apr 25, 2016 at 12:22:07PM +0100, Will Deacon wrote: > > > On Mon, Apr 04, 2016 at 02:19:54PM +0200, Jan Glauber wrote: > > > > can you have a look at these patches? > > > > > > Looks like Mark reviewed this last week -- are you planning to respin? > > > > Yes, of course. I just had no time yet and I'm a bit lost on how to > > proceed without using the NUMA node information which Mark did not like > > to be used. > > > > The only way to know which device is on which node would be to look > > at the PCI topology (which is also the source of the NUMA node_id). > > We could do this manually in order to not depend on CONFIG_NUMA, > > but I would like to know if that is acceptable before respinning the > > patches. > > That doesn't feel like it really addresses Mark's concerns -- it's just > another way to get the information that isn't a first-class PMU topology > description from firmware. > > Now, I don't actually mind using the NUMA topology so much in the cases > where it genuinely correlates with the PMU topology. My objection is more > that we end up sticking everything on node 0 if !CONFIG_NUMA, which could > result in working with an incorrect PMU topology and passing all of that > through to userspace. > > So I'd prefer either making the driver depend on NUMA, or at the very least > failing to probe the PMU if we discover a socketed system and NUMA is not > selected. Do either of those work as a compromise? > > Will That sounds like a good compromise. So I could do the following: 1) In the uncore setup check for CONFIG_NUMA, if set use the NUMA information to determine the device node 2) If CONFIG_NUMA is not set we check if we run on a socketed system a) In that case we return an error and give a message that CONFIG_NUMA needs to be enabled b) Otherwise we have a single node system and use node_id = 0 David noted that it would also be possible to extract the node id from the physical address of the device, but I'm not sure that classifies as 'first-class' topology description... --Jan