powerpc/perf: Add a shared interface to get gpci version and capabilities

This exposes a simple way to grab the firmware provided
collect_priveliged, ga, expanded, and lab capability bits. All of these
bits come in from the same gpci request, so we've exposed all of them.

Only the collect_priveliged bit is really used by the hv-gpci/hv-24x7
code, the other bits are simply exposed in sysfs to inform the user.
Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/perf/hv-common.c

+#include <asm/io.h>
+#include <asm/hvcall.h>
+
+#include "hv-gpci.h"
+#include "hv-common.h"
+
+unsigned long hv_perf_caps_get(struct hv_perf_caps *caps)
+{
+	unsigned long r;
+	struct p {
+		struct hv_get_perf_counter_info_params params;
+		struct cv_system_performance_capabilities caps;
+	} __packed __aligned(sizeof(uint64_t));
+
+	struct p arg = {
+		.params = {
+			.counter_request = cpu_to_be32(
+					CIR_SYSTEM_PERFORMANCE_CAPABILITIES),
+			.starting_index = cpu_to_be32(-1),
+			.counter_info_version_in = 0,
+		}
+	};
+
+	r = plpar_hcall_norets(H_GET_PERF_COUNTER_INFO,
+			       virt_to_phys(&arg), sizeof(arg));
+
+	if (r)
+		return r;
+
+	pr_devel("capability_mask: 0x%x\n", arg.caps.capability_mask);
+
+	caps->version = arg.params.counter_info_version_out;
+	caps->collect_privileged = !!arg.caps.perf_collect_privileged;
+	caps->ga = !!(arg.caps.capability_mask & CV_CM_GA);
+	caps->expanded = !!(arg.caps.capability_mask & CV_CM_EXPANDED);
+	caps->lab = !!(arg.caps.capability_mask & CV_CM_LAB);
+
+	return r;
+}

arch/powerpc/perf/hv-common.h

+#ifndef LINUX_POWERPC_PERF_HV_COMMON_H_
+#define LINUX_POWERPC_PERF_HV_COMMON_H_
+
+#include <linux/types.h>
+
+struct hv_perf_caps {
+	u16 version;
+	u16 collect_privileged:1,
+	    ga:1,
+	    expanded:1,
+	    lab:1,
+	    unused:12;
+};
+
+unsigned long hv_perf_caps_get(struct hv_perf_caps *caps);
+
+#endif