[SRU][J][PATCH v2 18/20] x86/CPU/AMD: Only apply Zenbleed fix for Zen2 during late microcode load

[Juerg Haefliger]

From: John Allen <john.allen at amd.com>

Commit

  f69759be251d ("x86/CPU/AMD: Move Zenbleed check to the Zen2 init function")

causes a bit in the DE_CFG MSR to get set erroneously after a microcode late
load.

The microcode late load path calls into amd_check_microcode() and subsequently
zen2_zenbleed_check(). Since the above commit removes the cpu_has_amd_erratum()
call from zen2_zenbleed_check(), this will cause all non-Zen2 CPUs to go
through the function and set the bit in the DE_CFG MSR.

Call into the Zenbleed fix path on Zen2 CPUs only.

  [ bp: Massage commit message, use cpu_feature_enabled(). ]

Fixes: f69759be251d ("x86/CPU/AMD: Move Zenbleed check to the Zen2 init function")
Signed-off-by: John Allen <john.allen at amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp at alien8.de>
Acked-by: Borislav Petkov (AMD) <bp at alien8.de>
Cc: <stable at vger.kernel.org>
Link: https://lore.kernel.org/r/20240923164404.27227-1-john.allen@amd.com
(cherry picked from commit ee4d4e8d2c3bec6ee652599ab31991055a72c322)
CVE-2024-53114
Signed-off-by: Juerg Haefliger <juerg.haefliger at canonical.com>
---
 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 6b0c11f3a37c..0a4cdcd0f4e3 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1363,7 +1363,8 @@ void amd_check_microcode(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 		return;
 
-	on_each_cpu(zenbleed_check_cpu, NULL, 1);
+	if (cpu_feature_enabled(X86_FEATURE_ZEN2))
+		on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }
 
 /*
-- 
2.48.1