On Tue, 2 Feb 2021 at 23:06, Suzuki K Poulose suzuki.poulose@arm.com wrote:
On 2/2/21 4:38 PM, Leo Yan wrote:
From: Suzuki K Poulose suzuki.poulose@arm.com
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@linaro.org Cc: Al Grant al.grant@arm.com Cc: Mike Leach mike.leach@linaro.org Cc: Leo Yan leo.yan@linaro.org Signed-off-by: Suzuki K Poulose suzuki.poulose@arm.com
You may add the following line here :
[ Added two config formats: contextid1, contextid2 ]
Signed-off-by: Leo Yan leo.yan@linaro.org
The patch as such looks good to me.
Suzuki
Reviewed-by: Mike Leach mike.leach@linaro.org
-- Mike Leach Principal Engineer, ARM Ltd. Manchester Design Centre. UK