Re: [PATCH v2 09/10] tools/perf: Add perf tools support for extended register capability in powerpc

On 08-Jul-2020, at 5:34 PM, Michael Ellerman [off-list ref] wrote:

Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>> writes:

quoted

From: Anju T Sudhakar <redacted>

Add extended regs to sample_reg_mask in the tool side to use
with `-I?` option. Perf tools side uses extended mask to display
the platform supported register names (with -I? option) to the user
and also send this mask to the kernel to capture the extended registers
in each sample. Hence decide the mask value based on the processor
version.

Signed-off-by: Anju T Sudhakar <redacted>
[Decide extended mask at run time based on platform]
Signed-off-by: Athira Rajeev <redacted>
Reviewed-by: Madhavan Srinivasan <redacted>

Will need an ack from perf tools folks, who are not on Cc by the looks.

quoted

diff --git a/tools/arch/powerpc/include/uapi/asm/perf_regs.h b/tools/arch/powerpc/include/uapi/asm/perf_regs.h
index f599064..485b1d5 100644
--- a/tools/arch/powerpc/include/uapi/asm/perf_regs.h
+++ b/tools/arch/powerpc/include/uapi/asm/perf_regs.h

@@ -48,6 +48,18 @@ enum perf_event_powerpc_regs {

	PERF_REG_POWERPC_DSISR,
	PERF_REG_POWERPC_SIER,
	PERF_REG_POWERPC_MMCRA,
-	PERF_REG_POWERPC_MAX,
+	/* Extended registers */
+	PERF_REG_POWERPC_MMCR0,
+	PERF_REG_POWERPC_MMCR1,
+	PERF_REG_POWERPC_MMCR2,
+	/* Max regs without the extended regs */
+	PERF_REG_POWERPC_MAX = PERF_REG_POWERPC_MMCRA + 1,

I don't really understand this idea of a max that's not the max.

Hi Michael

This is the MAX without extended regs. This is mainly used in `arch/powerpc/perf/perf_regs.c` to define pt_regs_offset ( to get index
for other regs ) and also is used to determine whether requested register is an extended reg while capturing data in sample
( in `perf_reg_value` )

Thanks
Athira

quoted

};
+
+#define PERF_REG_PMU_MASK	((1ULL << PERF_REG_POWERPC_MAX) - 1)
+
+/* PERF_REG_EXTENDED_MASK value for CPU_FTR_ARCH_300 */
+#define PERF_REG_PMU_MASK_300   (((1ULL << (PERF_REG_POWERPC_MMCR2 + 1)) - 1) \
+				- PERF_REG_PMU_MASK)
+
#endif /* _UAPI_ASM_POWERPC_PERF_REGS_H */

diff --git a/tools/perf/arch/powerpc/include/perf_regs.h b/tools/perf/arch/powerpc/include/perf_regs.h
index e18a355..46ed00d 100644
--- a/tools/perf/arch/powerpc/include/perf_regs.h
+++ b/tools/perf/arch/powerpc/include/perf_regs.h

@@ -64,7 +64,10 @@

	[PERF_REG_POWERPC_DAR] = "dar",
	[PERF_REG_POWERPC_DSISR] = "dsisr",
	[PERF_REG_POWERPC_SIER] = "sier",
-	[PERF_REG_POWERPC_MMCRA] = "mmcra"
+	[PERF_REG_POWERPC_MMCRA] = "mmcra",
+	[PERF_REG_POWERPC_MMCR0] = "mmcr0",
+	[PERF_REG_POWERPC_MMCR1] = "mmcr1",
+	[PERF_REG_POWERPC_MMCR2] = "mmcr2",
};

static inline const char *perf_reg_name(int id)

diff --git a/tools/perf/arch/powerpc/util/perf_regs.c b/tools/perf/arch/powerpc/util/perf_regs.c
index 0a52429..9179230 100644
--- a/tools/perf/arch/powerpc/util/perf_regs.c
+++ b/tools/perf/arch/powerpc/util/perf_regs.c

@@ -6,9 +6,14 @@

#include "../../../util/perf_regs.h"
#include "../../../util/debug.h"
+#include "../../../util/event.h"
+#include "../../../util/header.h"
+#include "../../../perf-sys.h"

#include <linux/kernel.h>

+#define PVR_POWER9		0x004E
+
const struct sample_reg sample_reg_masks[] = {
	SMPL_REG(r0, PERF_REG_POWERPC_R0),
	SMPL_REG(r1, PERF_REG_POWERPC_R1),

@@ -55,6 +60,9 @@

	SMPL_REG(dsisr, PERF_REG_POWERPC_DSISR),
	SMPL_REG(sier, PERF_REG_POWERPC_SIER),
	SMPL_REG(mmcra, PERF_REG_POWERPC_MMCRA),
+	SMPL_REG(mmcr0, PERF_REG_POWERPC_MMCR0),
+	SMPL_REG(mmcr1, PERF_REG_POWERPC_MMCR1),
+	SMPL_REG(mmcr2, PERF_REG_POWERPC_MMCR2),
	SMPL_REG_END
};

@@ -163,3 +171,50 @@ int arch_sdt_arg_parse_op(char *old_op, char **new_op)

	return SDT_ARG_VALID;
}
+
+uint64_t arch__intr_reg_mask(void)
+{
+	struct perf_event_attr attr = {
+		.type                   = PERF_TYPE_HARDWARE,
+		.config                 = PERF_COUNT_HW_CPU_CYCLES,
+		.sample_type            = PERF_SAMPLE_REGS_INTR,
+		.precise_ip             = 1,
+		.disabled               = 1,
+		.exclude_kernel         = 1,
+	};
+	int fd, ret;
+	char buffer[64];
+	u32 version;
+	u64 extended_mask = 0;
+
+	/* Get the PVR value to set the extended
+	 * mask specific to platform

Comment format is wrong, and punctuation please.

quoted

+	 */
+	get_cpuid(buffer, sizeof(buffer));
+	ret = sscanf(buffer, "%u,", &version);

This is powerpc specific code, why not just use mfspr(SPRN_PVR), rather
than redirecting via printf/sscanf.

quoted

+
+	if (ret != 1) {
+		pr_debug("Failed to get the processor version, unable to output extended registers\n");
+		return PERF_REGS_MASK;
+	}
+
+	if (version == PVR_POWER9)
+		extended_mask = PERF_REG_PMU_MASK_300;
+	else
+		return PERF_REGS_MASK;
+
+	attr.sample_regs_intr = extended_mask;
+	attr.sample_period = 1;
+	event_attr_init(&attr);
+
+	/*
+	 * check if the pmu supports perf extended regs, before
+	 * returning the register mask to sample.
+	 */
+	fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
+	if (fd != -1) {
+		close(fd);
+		return (extended_mask | PERF_REGS_MASK);
+	}
+	return PERF_REGS_MASK;

I think this would read a bit better like:

	mask = PERF_REGS_MASK;

	if (version == PVR_POWER9)
		extended_mask = PERF_REG_PMU_MASK_300;
       else
       	return mask;

       attr.sample_regs_intr = extended_mask;
       attr.sample_period = 1;
       event_attr_init(&attr);

       /*
         * check if the pmu supports perf extended regs, before
         * returning the register mask to sample.
         */
       fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
       if (fd != -1) {
               close(fd);
               mask |= extended_mask;
       }

	return mask;


cheers