[tip: x86/urgent] x86/CPU/AMD: Don't print reset reason in VMs

[tip-bot2 for Jason Andryuk]

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

Commit-ID:     ea51d1a4c31fc8320c34f897dc5296a0bfc5c7ca
Gitweb:        https://git.kernel.org/tip/ea51d1a4c31fc8320c34f897dc5296a0bfc5c7ca
Author:        Jason Andryuk <jason.andryuk@xxxxxxx>
AuthorDate:    Tue, 03 Nov 2026 20:30:25 -05:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Sun, 08 Nov 2026 23:25:40 -08:00

x86/CPU/AMD: Don't print reset reason in VMs

print_s5_reset_status_mmio() expects to read FCH MMIO on baremetal.  VMs don't
have emulated FCH registers, so there is nothing to check.  Add an early exit
when running on a hypervisor.

The real motivation is Xen PV domUs can't boot on Zen CPUs.  PV domUs PTEs
contain system physical addresses - they don't have the concept of guest
physical addresses.  domUs can only map physical addresses they are assigned, so
a domU fails to map the FCH MMIO addresses.

However set_pte() does not return failure, so ioremap() returns a pointer while
the PTEs are unpopulated.  print_s5_reset_status_mmio() faults when reading
through the pointer, breaking the boot.

Limit the reset reason printing to baremetal only where it actually makes sense.

  [ bp: Massage commit message. ]

Fixes: ab8131028710 ("x86/CPU/AMD: Print the reason for the last reset")
Suggested-by: Borislav Petkov <bp@xxxxxxxxx>
Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Mario Limonciello (AMD) <superm1@xxxxxxxxxx>
Reviewed-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20261104013026.185392-1-jason.andryuk@xxxxxxx
---
 arch/x86/kernel/cpu/amd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 3972966..2f7efd3 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1362,7 +1362,8 @@ static __init int print_s5_reset_status_mmio(void)
 	u32 value;
 	int i;
 
-	if (!cpu_feature_enabled(X86_FEATURE_ZEN))
+	if (!cpu_feature_enabled(X86_FEATURE_ZEN) ||
+	    cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
 		return 0;
 
 	addr = ioremap(FCH_PM_BASE + FCH_PM_S5_RESET_STATUS, sizeof(value));