tools/perf/powerpc/util: Add support to handle compatible mode PVR for perf json events

JIRA: https://issues.redhat.com/browse/RHEL-77935

upstream
========
commit 54f9aa1
Author: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Date: Thu Oct 10 20:21:07 2024 +0530

description
===========
perf list picks the events supported for specific platform
from pmu-events/arch/powerpc/<platform>. Example power10 events
are in pmu-events/arch/powerpc/power10, power9 events are part
of pmu-events/arch/powerpc/power9. The decision of which
platform to pick is determined based on PVR value in powerpc.
The PVR value is matched from pmu-events/arch/powerpc/mapfile.csv

Example:

Format:
	PVR,Version,JSON/file/pathname,Type

0x004[bcd][[:xdigit:]]{4},1,power8,core
0x0066[[:xdigit:]]{4},1,power8,core
0x004e[[:xdigit:]]{4},1,power9,core
0x0080[[:xdigit:]]{4},1,power10,core
0x0082[[:xdigit:]]{4},1,power10,core

The code gets the PVR from system using get_cpuid_str function
in arch/powerpc/util/headers.c ( from SPRN_PVR ) and compares
with value from mapfile.csv
In case of compat mode, say when partition is booted in a power9
mode when the system is a power10, this picks incorrectly. Because
PVR will point to power10 where as it should pick events from power9
folder. To support generic events, add new folder
pmu-events/arch/powerpc/compat to contain the ISA architected events
which is supported in compat mode. Also return 0x00ffffff as pvr
when booted in compat mode. Based on this pvr value, json will
pick events from pmu-events/arch/powerpc/compat

    Suggested-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
    Tested-by: Disha Goel<disgoel@linux.ibm.com>
    Cc: akanksha@linux.ibm.com
    Cc: hbathini@linux.ibm.com
    Cc: kjain@linux.ibm.com
    Cc: linuxppc-dev@lists.ozlabs.org
    Link: https://lore.kernel.org/r/20241010145107.51211-2-atrajeev@linux.vnet.ibm.com
    Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Signed-off-by: Michael Petlan <mpetlan@redhat.com>

Author: rfmvh

tools/perf/arch/powerpc/util/header.c

@@ -10,6 +10,18 @@
 #include "utils_header.h"
 #include "metricgroup.h"
 #include <api/fs/fs.h>
+#include <sys/auxv.h>
+
+static bool is_compat_mode(void)
+{
+	u64 base_platform = getauxval(AT_BASE_PLATFORM);
+	u64 platform = getauxval(AT_PLATFORM);
+
+	if (!strcmp((char *)platform, (char *)base_platform))
+		return false;
+
+	return true;
+}
 
 int
 get_cpuid(char *buffer, size_t sz)
@@ -33,8 +45,26 @@ char *
 get_cpuid_str(struct perf_pmu *pmu __maybe_unused)
 {
 	char *bufp;
+	unsigned long pvr;
+
+	/*
+	 * IBM Power System supports compatible mode. That is
+	 * Nth generation platform can support previous generation
+	 * OS in a mode called compatibile mode. For ex. LPAR can be
+	 * booted in a Power9 mode when the system is a Power10.
+	 *
+	 * In the compatible mode, care must be taken when generating
+	 * PVR value. When read, PVR will be of the AT_BASE_PLATFORM
+	 * To support generic events, return 0x00ffffff as pvr when
+	 * booted in compat mode. Based on this pvr value, json will
+	 * pick events from pmu-events/arch/powerpc/compat
+	 */
+	if (!is_compat_mode())
+		pvr = mfspr(SPRN_PVR);
+	else
+		pvr = 0x00ffffff;
 
-	if (asprintf(&bufp, "0x%.8lx", mfspr(SPRN_PVR)) < 0)
+	if (asprintf(&bufp, "0x%.8lx", pvr) < 0)
 		bufp = NULL;
 
 	return bufp;