linux-kernel - [tip: x86/urgent] x86/CPU/AMD: Ignore invalid reset reason value

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Message-ID: <175552872343.1420.5386589162109047550.tip-bot2@tip-bot2>
Date: Mon, 18 Aug 2025 14:52:03 -0000
From: "tip-bot2 for Yazen Ghannam" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Libing He <libhe@...hat.com>, Yazen Ghannam <yazen.ghannam@....com>,
 "Borislav Petkov (AMD)" <bp@...en8.de>,
 Mario Limonciello <mario.limonciello@....com>, stable@...r.kernel.org,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/CPU/AMD: Ignore invalid reset reason value

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     e9576e078220c50ace9e9087355423de23e25fa5
Gitweb:        https://git.kernel.org/tip/e9576e078220c50ace9e9087355423de23e25fa5
Author:        Yazen Ghannam <yazen.ghannam@....com>
AuthorDate:    Mon, 21 Jul 2025 18:11:54 
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Mon, 18 Aug 2025 16:36:59 +02:00

x86/CPU/AMD: Ignore invalid reset reason value

The reset reason value may be "all bits set", e.g. 0xFFFFFFFF. This is a
commonly used error response from hardware. This may occur due to a real
hardware issue or when running in a VM.

The user will see all reset reasons reported in this case.

Check for an error response value and return early to avoid decoding
invalid data.

Also, adjust the data variable type to match the hardware register size.

Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
Reported-by: Libing He <libhe@...hat.com>
Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/20250721181155.3536023-1-yazen.ghannam@amd.com
---
 arch/x86/kernel/cpu/amd.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a5ece6e..a6f88ca 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1326,8 +1326,8 @@ static const char * const s5_reset_reason_txt[] = {
 
 static __init int print_s5_reset_status_mmio(void)
 {
-	unsigned long value;
 	void __iomem *addr;
+	u32 value;
 	int i;
 
 	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
@@ -1340,12 +1340,16 @@ static __init int print_s5_reset_status_mmio(void)
 	value = ioread32(addr);
 	iounmap(addr);
 
+	/* Value with "all bits set" is an error response and should be ignored. */
+	if (value == U32_MAX)
+		return 0;
+
 	for (i = 0; i < ARRAY_SIZE(s5_reset_reason_txt); i++) {
 		if (!(value & BIT(i)))
 			continue;
 
 		if (s5_reset_reason_txt[i]) {
-			pr_info("x86/amd: Previous system reset reason [0x%08lx]: %s\n",
+			pr_info("x86/amd: Previous system reset reason [0x%08x]: %s\n",
 				value, s5_reset_reason_txt[i]);
 		}
 	}