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@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

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a5ece6ebe8a74a706bf3e98e1e99603c2a655c3c..a6f88ca1a6b495282e9284727bf043cbb8741d59 100644 (file)
--- 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]);
                }
        }