linux-kernel - [PATCH v2] x86: microcode: fix return value for microcode late loading

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Message-Id: <1587497318-4438-1-git-send-email-mihai.carabas@oracle.com>
Date:   Tue, 21 Apr 2020 22:28:38 +0300
From:   Mihai Carabas <mihai.carabas@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Mihai Carabas <mihai.carabas@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v2] x86: microcode: fix return value for microcode late loading

The return value from stop_machine might not be consistent.

stop_machine_cpuslocked returns:
- zero if all functions have returned 0
- a non-zero value if at least one of the functions returned
a non-zero value

There is no way to know if it is negative or positive. So make
__reload_late return 0 on success, or negative otherwise.

Signed-off-by: Mihai Carabas <mihai.carabas@...cle.com>
---
Changes in v2:
- do not print anything on UCODE_NFOUND as microcode not found
is not an error

 arch/x86/kernel/cpu/microcode/core.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 7019d4b..a2ae3da 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -545,8 +545,7 @@ static int __wait_for_cpus(atomic_t *t, long long timeout)
 /*
  * Returns:
  * < 0 - on error
- *   0 - no update done
- *   1 - microcode was updated
+ *   0 - success (no update done or microcode was updated)
  */
 static int __reload_late(void *info)
 {
@@ -576,8 +575,8 @@ static int __reload_late(void *info)
 	if (err > UCODE_NFOUND) {
 		pr_warn("Error reloading microcode on CPU %d\n", cpu);
 		ret = -1;
-	} else if (err == UCODE_UPDATED || err == UCODE_OK) {
-		ret = 1;
+	} else if (err == UCODE_NFOUND) {
+		ret = -1;
 	}
 
 wait_for_siblings:
@@ -608,7 +607,7 @@ static int microcode_reload_late(void)
 	atomic_set(&late_cpus_out, 0);
 
 	ret = stop_machine_cpuslocked(__reload_late, NULL, cpu_online_mask);
-	if (ret > 0)
+	if (ret == 0)
 		microcode_check();
 
 	pr_info("Reload completed, microcode revision: 0x%x\n", boot_cpu_data.microcode);
@@ -649,7 +648,7 @@ static ssize_t reload_store(struct device *dev,
 put:
 	put_online_cpus();
 
-	if (ret >= 0)
+	if (ret == 0)
 		ret = size;
 
 	return ret;
-- 
1.8.3.1