Re: [PATCH v3 7/8] perf cs-etm: Detect pid in VMID for kernel running at EL2

Mathieu Poirier
2021-02-08T20:34:39Z

On Sat, Feb 06, 2021 at 11:08:32PM +0800, Leo Yan wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
>
> The PID of the task could be traced as VMID when the kernel is running
> at EL2. Teach the decoder to look for VMID when the CONTEXTIDR (Arm32)
> or CONTEXTIDR_EL1 (Arm64) is invalid but we have a valid VMID.
>
> Cc: Mike Leach <mike.leach@linaro.org>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Al Grant <al.grant@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
> Co-developed-by: Leo Yan <leo.yan@linaro.org>
> Signed-off-by: Leo Yan <leo.yan@linaro.org>

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>

> ---
> .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 38 +++++++++++++++++--
> 1 file changed, 34 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> index 3f4bc4050477..4052c9ce6e2f 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -6,6 +6,7 @@
> * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
> */
>
> +#include <linux/coresight-pmu.h>
> #include <linux/err.h>
> #include <linux/list.h>
> #include <linux/zalloc.h>
> @@ -491,13 +492,42 @@ cs_etm_decoder__set_tid(struct cs_etm_queue *etmq,
> const ocsd_generic_trace_elem *elem,
> const uint8_t trace_chan_id)
> {
> - pid_t tid;
> + pid_t tid = -1;
> + static u64 pid_fmt;
> + int ret;
>
> - /* Ignore PE_CONTEXT packets that don't have a valid contextID */
> - if (!elem->context.ctxt_id_valid)
> + /*
> + * As all the ETMs run at the same exception level, the system should
> + * have the same PID format crossing CPUs. So cache the PID format
> + * and reuse it for sequential decoding.
> + */
> + if (!pid_fmt) {
> + ret = cs_etm__get_pid_fmt(trace_chan_id, &pid_fmt);
> + if (ret)
> + return OCSD_RESP_FATAL_SYS_ERR;
> + }
> +
> + /*
> + * Process the PE_CONTEXT packets if we have a valid contextID or VMID.
> + * If the kernel is running at EL2, the PID is traced in CONTEXTIDR_EL2
> + * as VMID, Bit ETM_OPT_CTXTID2 is set in this case.
> + */
> + switch (pid_fmt) {
> + case BIT(ETM_OPT_CTXTID):
> + if (elem->context.ctxt_id_valid)
> + tid = elem->context.context_id;
> + break;
> + case BIT(ETM_OPT_CTXTID2):
> + if (elem->context.vmid_valid)
> + tid = elem->context.vmid;
> + break;
> + default:
> + break;
> + }
> +
> + if (tid == -1)
> return OCSD_RESP_CONT;
>
> - tid = elem->context.context_id;
> if (cs_etm__etmq_set_tid(etmq, tid, trace_chan_id))
> return OCSD_RESP_FATAL_SYS_ERR;
>
> --
> 2.25.1