Hi David,
Thanks for the review.
On 06/16/2015 08:23 PM, David Ahern wrote:
On 6/15/15 8:50 PM, Hemant Kumar wrote:
+/*
+ * Get the instruction pointer from the tracepoint data
+ */
+u64 arch__get_ip(struct perf_evsel *evsel, struct perf_sample *data)
+{
+ u64 tp_ip = data->ip;
+ int trap;
+
+ if (!strcmp(KVMPPC_EXIT, evsel->name)) {
+ trap = raw_field_value(evsel->tp_format, "trap",
data->raw_data);
+
+ if (trap == HV_DECREMENTER)
+ tp_ip = raw_field_value(evsel->tp_format, "pc",
+ data->raw_data);
+ }
+ return tp_ip;
+}
You can tie a handler to an event; see builtin-trace.c for example
(evsel->handler = handler). Then have the sample handler call it (e.g,
see trace__process_sample). Then you don't have to check event names
on each pass like this and just do event based processing.
+
+/*
+ * Get the HV and PR bits and accordingly, determine the cpumode
+ */
+u8 arch__get_cpumode(union perf_event *event, struct perf_evsel *evsel,
+ struct perf_sample *data)
+{
+ unsigned long hv, pr, msr;
+ u8 cpumode = event->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;
+
+ if (strcmp(KVMPPC_EXIT, evsel->name))
+ goto ret;
+
+ if (data->raw_data)
+ msr = raw_field_value(evsel->tp_format, "msr", data->raw_data);
+ else
+ goto ret;
+
+ hv = msr & ((long unsigned)1 << (PPC_MAX - HV_BIT));
+ pr = msr & ((long unsigned)1 << (PPC_MAX - PR_BIT));
+
+ if (!hv && pr)
+ cpumode = PERF_RECORD_MISC_GUEST_USER;
+ else
+ cpumode = PERF_RECORD_MISC_GUEST_KERNEL;
+ret:
+ return cpumode;
+}
Why isn't that set properly kernel side when the sample is generated?
Because, this depends on the kernel tracepoint "kvm_hv:kvm_guest_exit".
perf_prepare_sample() in the kernel side sets the event->header.misc
field to
PERF_RECORD_MISC_KERNEL through perf_misc_flags(pt_regs). In case of
tracepoints which always get hit in the host kernel context, the
perf_misc_flags() will always return PERF_RECORD_MISC_KERNEL.
IMHO we will rather have to set the cpumode in the user space for this
tracepoint
and we can't depend on the event->header.misc field for this case.
What would you suggest?
--
Thanks,
Hemant Kumar
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