On Tue, 2 Feb 2021 at 23:06, Suzuki K Poulose <suzuki.poulose@xxxxxxx> wrote: > > On 2/2/21 4:38 PM, Leo Yan wrote: > > From: Suzuki K Poulose <suzuki.poulose@xxxxxxx> > > > > When the kernel is running at EL2, the PID is stored in CONTEXTIDR_EL2. > > So, tracing CONTEXTIDR_EL1 doesn't give us the pid of the process. > > Thus we should trace the VMID with VMIDOPT set to trace CONTEXTIDR_EL2 > > instead of CONTEXTIDR_EL1. Given that we have an existing config > > option "contextid" and this will be useful for tracing virtual machines > > (when we get to support virtualization). > > > > So instead, this patch extends option CTXTID with an extra bit > > ETM_OPT_CTXTID2 (bit 15), thus on an EL2 kernel, we will have another > > bit available for the perf tool: ETM_OPT_CTXTID is for kernel running in > > EL1, ETM_OPT_CTXTID2 is used when kernel runs in EL2 with VHE enabled. > > > > The tool must be backward compatible for users, i.e, "contextid" today > > traces PID and that should remain the same; for this purpose, the perf > > tool is updated to automatically set corresponding bit for the > > "contextid" config, therefore, the user doesn't have to bother which EL > > the kernel is running. > > > > i.e, perf record -e cs_etm/contextid/u -- > > > > will always do the "pid" tracing, independent of the kernel EL. > > > > The driver parses the format "contextid", which traces CONTEXTIDR_EL1 > > for ETM_OPT_CTXTID (on EL1 kernel) and traces CONTEXTIDR_EL2 for > > ETM_OPT_CTXTID2 (on EL2 kernel). > > > > Besides the enhancement for format "contexid", extra two formats are > > introduced: "contextid1" and "contextid2". This considers to support > > tracing both CONTEXTIDR_EL1 and CONTEXTIDR_EL2 when the kernel is > > running at EL2. Finally, the PMU formats are defined as follow: > > > > "contextid1": Available on both EL1 kernel and EL2 kernel. When the > > kernel is running at EL1, "contextid1" enables the PID > > tracing; when the kernel is running at EL2, this enables > > tracing the PID of guest applications. > > > > "contextid2": Only usable when the kernel is running at EL2. When > > selected, enables PID tracing on EL2 kernel. > > > > "contextid": Will be an alias for the option that enables PID > > tracing. I.e, > > contextid == contextid1, on EL1 kernel. > > contextid == contextid2, on EL2 kernel. > > > > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> > > Cc: Al Grant <al.grant@xxxxxxx> > > Cc: Mike Leach <mike.leach@xxxxxxxxxx> > > Cc: Leo Yan <leo.yan@xxxxxxxxxx> > > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx> > > You may add the following line here : > > [ Added two config formats: contextid1, contextid2 ] > > > Signed-off-by: Leo Yan <leo.yan@xxxxxxxxxx> > > The patch as such looks good to me. > > Suzuki Reviewed-by: Mike Leach <mike.leach@xxxxxxxxxx> -- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK
