RISC-V: Align SBI probe implementation with spec

sbi_probe_extension() is specified with "Returns 0 if the given SBI
extension ID (EID) is not available, or 1 if it is available unless
defined as any other non-zero value by the implementation."
Additionally, sbiret.value is a long. Fix the implementation to
ensure any nonzero long value is considered a success, rather
than only positive int values.

Fixes: b9dcd9e ("RISC-V: Add basic support for SBI v0.2")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230427163626.101042-1-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Andrew Jones

arch/riscv/include/asm/sbi.h

@@ -295,7 +295,7 @@ int sbi_remote_hfence_vvma_asid(const struct cpumask *cpu_mask,
 				unsigned long start,
 				unsigned long size,
 				unsigned long asid);
-int sbi_probe_extension(int ext);
+long sbi_probe_extension(int ext);
 
 /* Check if current SBI specification version is 0.1 or not */
 static inline int sbi_spec_is_0_1(void)

arch/riscv/kernel/cpu_ops.c

@@ -27,7 +27,7 @@ const struct cpu_operations cpu_ops_spinwait = {
 void __init cpu_set_ops(int cpuid)
 {
 #if IS_ENABLED(CONFIG_RISCV_SBI)
-	if (sbi_probe_extension(SBI_EXT_HSM) > 0) {
+	if (sbi_probe_extension(SBI_EXT_HSM)) {
 		if (!cpuid)
 			pr_info("SBI HSM extension detected\n");
 		cpu_ops[cpuid] = &cpu_ops_sbi;

arch/riscv/kernel/sbi.c

@@ -524,19 +524,18 @@ static void sbi_srst_power_off(void)
  * sbi_probe_extension() - Check if an SBI extension ID is supported or not.
  * @extid: The extension ID to be probed.
  *
- * Return: Extension specific nonzero value f yes, -ENOTSUPP otherwise.
+ * Return: 1 or an extension specific nonzero value if yes, 0 otherwise.
  */
-int sbi_probe_extension(int extid)
+long sbi_probe_extension(int extid)
 {
 	struct sbiret ret;
 
 	ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, extid,
 			0, 0, 0, 0, 0);
 	if (!ret.error)
-		if (ret.value)
-			return ret.value;
+		return ret.value;
 
-	return -ENOTSUPP;
+	return 0;
 }
 EXPORT_SYMBOL(sbi_probe_extension);
 
@@ -599,26 +598,26 @@ void __init sbi_init(void)
 	if (!sbi_spec_is_0_1()) {
 		pr_info("SBI implementation ID=0x%lx Version=0x%lx\n",
 			sbi_get_firmware_id(), sbi_get_firmware_version());
-		if (sbi_probe_extension(SBI_EXT_TIME) > 0) {
+		if (sbi_probe_extension(SBI_EXT_TIME)) {
 			__sbi_set_timer = __sbi_set_timer_v02;
 			pr_info("SBI TIME extension detected\n");
 		} else {
 			__sbi_set_timer = __sbi_set_timer_v01;
 		}
-		if (sbi_probe_extension(SBI_EXT_IPI) > 0) {
+		if (sbi_probe_extension(SBI_EXT_IPI)) {
 			__sbi_send_ipi	= __sbi_send_ipi_v02;
 			pr_info("SBI IPI extension detected\n");
 		} else {
 			__sbi_send_ipi	= __sbi_send_ipi_v01;
 		}
-		if (sbi_probe_extension(SBI_EXT_RFENCE) > 0) {
+		if (sbi_probe_extension(SBI_EXT_RFENCE)) {
 			__sbi_rfence	= __sbi_rfence_v02;
 			pr_info("SBI RFENCE extension detected\n");
 		} else {
 			__sbi_rfence	= __sbi_rfence_v01;
 		}
 		if ((sbi_spec_version >= sbi_mk_version(0, 3)) &&
-		    (sbi_probe_extension(SBI_EXT_SRST) > 0)) {
+		    sbi_probe_extension(SBI_EXT_SRST)) {
 			pr_info("SBI SRST extension detected\n");
 			pm_power_off = sbi_srst_power_off;
 			sbi_srst_reboot_nb.notifier_call = sbi_srst_reboot;

arch/riscv/kvm/main.c

@@ -75,7 +75,7 @@ static int __init riscv_kvm_init(void)
 		return -ENODEV;
 	}
 
-	if (sbi_probe_extension(SBI_EXT_RFENCE) <= 0) {
+	if (!sbi_probe_extension(SBI_EXT_RFENCE)) {
 		kvm_info("require SBI RFENCE extension\n");
 		return -ENODEV;
 	}

drivers/cpuidle/cpuidle-riscv-sbi.c

@@ -613,7 +613,7 @@ static int __init sbi_cpuidle_init(void)
 	 * 2) SBI HSM extension is available
 	 */
 	if ((sbi_spec_version < sbi_mk_version(0, 3)) ||
-	    sbi_probe_extension(SBI_EXT_HSM) <= 0) {
+	    !sbi_probe_extension(SBI_EXT_HSM)) {
 		pr_info("HSM suspend not available\n");
 		return 0;
 	}

drivers/perf/riscv_pmu_sbi.c

@@ -924,7 +924,7 @@ static int __init pmu_sbi_devinit(void)
 	struct platform_device *pdev;
 
 	if (sbi_spec_version < sbi_mk_version(0, 3) ||
-	    sbi_probe_extension(SBI_EXT_PMU) <= 0) {
+	    !sbi_probe_extension(SBI_EXT_PMU)) {
 		return 0;
 	}