On Tue, Jul 15, 2025 at 02:04:18PM +0100, James Clark wrote: > On 14/07/2025 3:04 pm, Will Deacon wrote: > > On Thu, Jun 05, 2025 at 11:49:05AM +0100, James Clark wrote: > > > @@ -406,6 +416,9 @@ static u64 arm_spe_event_to_pmsfcr(struct perf_event *event) > > > if (ATTR_CFG_GET_FLD(attr, inv_event_filter)) > > > reg |= PMSFCR_EL1_FnE; > > > + if (ATTR_CFG_GET_FLD(attr, data_src_filter)) > > > + reg |= PMSFCR_EL1_FDS; > > > > Is the polarity correct here? The description of PMSDSFR_EL1.S<m> suggests > > that setting bits to 1 _excludes_ the FDS filtering. > > > > Setting filter bits to 1 means that samples matching are included. Setting > bits to 0 means that they are excluded. And PMSFCR_EL1.FDS enables filtering > as a whole, so if the user sets any filter bit to 1 we want to enable > filtering: > > PMSDSFR_EL1.S<m> > > 0b0 If PMSFCR_EL1.FDS is 1, do not record load operations that have > bits [5:0] of the Data Source packet set to <m>. > > 0b1 Load operations with Data Source <m> are unaffected by > PMSFCR_EL1.FDS. > > I think it's all the right way around and it ends up being the same as the > other filters in SPE. Because we're using any bit being set to enable the > filtering, the only thing you can't do is enable filtering with a 0 filter, > but I didn't think that was useful. See the previous discussion on this > here: > https://lore.kernel.org/all/5752f039-51c1-4452-b5df-03ff06da7be3@xxxxxxxxxx/ > > Reading the "Data source filtering" section in the docs change at the end > might help too. Sorry, but I still don't get it :/ afaict, if any of the bits in 'data_src_filter' are _zero_ then we should set PMSFCR_EL1.FDS. That also means that a mask of zero means all loads are filtered, which is what the architecture says and is what we should provide to userspace. Will
