linux-kernel - [PATCH 2/9] cpu/SMT: Move smt/control simple exit cases earlier

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Date:   Thu, 25 May 2023 01:56:23 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     <linux-kernel@...r.kernel.org>
Cc:     <linuxppc-dev@...ts.ozlabs.org>, <linux-arch@...r.kernel.org>,
        <ldufour@...ux.ibm.com>, <tglx@...utronix.de>, bp@...en8.de,
        dave.hansen@...ux.intel.com, mingo@...hat.com, x86@...nel.org
Subject: [PATCH 2/9] cpu/SMT: Move smt/control simple exit cases earlier

Move the simple exit cases, ie. which don't depend on the value written,
earlier in the function. That makes it clearer that regardless of the
input those states can not be transitioned out of.

That does have a user-visible effect, in that the error returned will
now always be EPERM/ENODEV for those states, regardless of the value
written. Previously writing an invalid value would return EINVAL even
when in those states.

Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
---
 kernel/cpu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/cpu.c b/kernel/cpu.c
index f4a2c5845bcb..01398ce3e131 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2481,6 +2481,12 @@ __store_smt_control(struct device *dev, struct device_attribute *attr,
 {
 	int ctrlval, ret;
 
+	if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
+		return -EPERM;
+
+	if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
+		return -ENODEV;
+
 	if (sysfs_streq(buf, "on"))
 		ctrlval = CPU_SMT_ENABLED;
 	else if (sysfs_streq(buf, "off"))
@@ -2490,12 +2496,6 @@ __store_smt_control(struct device *dev, struct device_attribute *attr,
 	else
 		return -EINVAL;
 
-	if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
-		return -EPERM;
-
-	if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
-		return -ENODEV;
-
 	ret = lock_device_hotplug_sysfs();
 	if (ret)
 		return ret;
-- 
2.40.1