powerpc/perf: MMCR0 control for PMU registers under PMCC=00

PowerISA v3.1 introduces new control bit (PMCCEXT) for restricting
access to group B PMU registers in problem state when
MMCR0 PMCC=0b00. In problem state and when MMCR0 PMCC=0b00,
setting the Monitor Mode Control Register bit 54 (MMCR0 PMCCEXT),
will restrict read permission on Group B Performance Monitor
Registers (SIER, SIAR, SDAR and MMCR1). When this bit is set to zero,
group B registers will be readable. In other platforms (like power9),
the older behaviour is retained where group B PMU SPRs are readable.

Patch adds support for MMCR0 PMCCEXT bit in power10 by enabling
this bit during boot and during the PMU event enable/disable callback
functions.
Signed-off-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1606409684-1589-8-git-send-email-atrajeev@linux.vnet.ibm.com

arch/powerpc/include/asm/reg.h

@@ -864,6 +864,7 @@
 #define   MMCR0_BHRBA	0x00200000UL /* BHRB Access allowed in userspace */
 #define   MMCR0_EBE	0x00100000UL /* Event based branch enable */
 #define   MMCR0_PMCC	0x000c0000UL /* PMC control */
+#define   MMCR0_PMCCEXT	ASM_CONST(0x00000200) /* PMCCEXT control */
 #define   MMCR0_PMCC_U6	0x00080000UL /* PMC1-6 are R/W by user (PR) */
 #define   MMCR0_PMC1CE	0x00008000UL /* PMC1 count enable*/
 #define   MMCR0_PMCjCE	ASM_CONST(0x00004000) /* PMCj count enable*/

arch/powerpc/kernel/cpu_setup_power.c

@@ -123,6 +123,7 @@ static void init_PMU_ISA31(void)
 {
 	mtspr(SPRN_MMCR3, 0);
 	mtspr(SPRN_MMCRA, MMCRA_BHRB_DISABLE);
+	mtspr(SPRN_MMCR0, MMCR0_PMCCEXT);
 }
 
 /*

arch/powerpc/kernel/dt_cpu_ftrs.c

@@ -454,6 +454,7 @@ static void init_pmu_power10(void)
 
 	mtspr(SPRN_MMCR3, 0);
 	mtspr(SPRN_MMCRA, MMCRA_BHRB_DISABLE);
+	mtspr(SPRN_MMCR0, MMCR0_PMCCEXT);
 }
 
 static int __init feat_enable_pmu_power10(struct dt_cpu_feature *f)

arch/powerpc/perf/core-book3s.c

@@ -95,6 +95,7 @@ static unsigned int freeze_events_kernel = MMCR0_FCS;
 #define SPRN_SIER3		0
 #define MMCRA_SAMPLE_ENABLE	0
 #define MMCRA_BHRB_DISABLE     0
+#define MMCR0_PMCCEXT		0
 
 static inline unsigned long perf_ip_adjust(struct pt_regs *regs)
 {
@@ -1273,6 +1274,9 @@ static void power_pmu_disable(struct pmu *pmu)
 		val |= MMCR0_FC;
 		val &= ~(MMCR0_EBE | MMCR0_BHRBA | MMCR0_PMCC | MMCR0_PMAO |
 			 MMCR0_FC56);
+		/* Set mmcr0 PMCCEXT for p10 */
+		if (ppmu->flags & PPMU_ARCH_31)
+			val |= MMCR0_PMCCEXT;
 
 		/*
 		 * The barrier is to make sure the mtspr has been

arch/powerpc/perf/isa207-common.c

@@ -558,6 +558,14 @@ int isa207_compute_mmcr(u64 event[], int n_ev,
 	if (!(pmc_inuse & 0x60))
 		mmcr->mmcr0 |= MMCR0_FC56;
 
+	/*
+	 * Set mmcr0 (PMCCEXT) for p10 which
+	 * will restrict access to group B registers
+	 * when MMCR0 PMCC=0b00.
+	 */
+	if (cpu_has_feature(CPU_FTR_ARCH_31))
+		mmcr->mmcr0 |= MMCR0_PMCCEXT;
+
 	mmcr->mmcr1 = mmcr1;
 	mmcr->mmcra = mmcra;
 	mmcr->mmcr2 = mmcr2;