RISC-V: Re-enable counter access from userspace

These counters were part of the ISA when we froze the uABI, removing
them breaks userspace.

Link: https://lore.kernel.org/all/YxEhC%2FmDW1lFt36J@aurel32.net/
Fixes: e9991434 ("RISC-V: Add perf platform driver based on SBI PMU extension")
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20220928131807.30386-1-palmer@rivosinc.com
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

drivers/perf/riscv_pmu_sbi.c

@@ -652,8 +652,11 @@ static int pmu_sbi_starting_cpu(unsigned int cpu, struct hlist_node *node)
 	struct riscv_pmu *pmu = hlist_entry_safe(node, struct riscv_pmu, node);
 	struct cpu_hw_events *cpu_hw_evt = this_cpu_ptr(pmu->hw_events);
 
-	/* Enable the access for TIME csr only from the user mode now */
-	csr_write(CSR_SCOUNTEREN, 0x2);
+	/*
+	 * Enable the access for CYCLE, TIME, and INSTRET CSRs from userspace,
+	 * as is necessary to maintain uABI compatibility.
+	 */
+	csr_write(CSR_SCOUNTEREN, 0x7);
 
 	/* Stop all the counters so that they can be enabled from perf */
 	pmu_sbi_stop_all(pmu);