x86/CPU/AMD: Ignore invalid reset reason value

JIRA: https://issues.redhat.com/browse/RHEL-101301

commit e9576e0
Author: Yazen Ghannam <yazen.ghannam@amd.com>
Date:   Mon Jul 21 18:11:54 2025 +0000

    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: ab81310 ("x86/CPU/AMD: Print the reason for the last reset")
    Reported-by: Libing He <libhe@redhat.com>
    Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
    Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
    Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
    Cc: stable@vger.kernel.org
    Link: https://lore.kernel.org/20250721181155.3536023-1-yazen.ghannam@amd.com

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

arch/x86/kernel/cpu/amd.c

@@ -1249,8 +1249,8 @@ 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))
@@ -1263,12 +1263,16 @@ 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]);
 		}
 	}