Subject: Re: [RFC PATCH] perf/kvm: Guest Symbol Resolution for powerpc

From: David Ahern <[email-masked]>
Date: Tue, 16 Jun 2015 08:53:55 -0600

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?

David