drivers: perf: Fix smp_processor_id() use in preemptible code

As reported in [1], the use of smp_processor_id() in
pmu_sbi_device_probe() must be protected by disabling the preemption, so
simple use get_cpu()/put_cpu() instead.

Reported-by: Nam Cao <namcao@linutronix.de>
Closes: https://lore.kernel.org/linux-riscv/20240820074925.ReMKUPP3@linutronix.de/ [1]
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Nam Cao <namcao@linutronix.de>
Fixes: a862521 ("drivers/perf: riscv: Implement SBI PMU snapshot function")
Reported-by: Andrea Parri <parri.andrea@gmail.com>
Tested-by: Andrea Parri <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20240826165210.124696-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Alexandre Ghiti

drivers/perf/riscv_pmu_sbi.c

@@ -1373,11 +1373,15 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 
 	/* SBI PMU Snapsphot is only available in SBI v2.0 */
 	if (sbi_v2_available) {
+		int cpu;
+
 		ret = pmu_sbi_snapshot_alloc(pmu);
 		if (ret)
 			goto out_unregister;
 
-		ret = pmu_sbi_snapshot_setup(pmu, smp_processor_id());
+		cpu = get_cpu();
+
+		ret = pmu_sbi_snapshot_setup(pmu, cpu);
 		if (ret) {
 			/* Snapshot is an optional feature. Continue if not available */
 			pmu_sbi_snapshot_free(pmu);
@@ -1391,6 +1395,7 @@ static int pmu_sbi_device_probe(struct platform_device *pdev)
 			 */
 			static_branch_enable(&sbi_pmu_snapshot_available);
 		}
+		put_cpu();
 	}
 
 	register_sysctl("kernel", sbi_pmu_sysctl_table);