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

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

[John Allen]

A problem was introduced with commit f69759be251d ("x86/CPU/AMD: Move
Zenbleed check to the Zen2 init function") where a bit in the DE_CFG MSR
is getting set after a microcode late load.

The problem seems to be that the microcode late load path calls into
amd_check_microcode() and subsequently zen2_zenbleed_check(). Since the
patch removes the cpu_has_amd_erratum() check 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.

Fixes: f69759be251d ("x86/CPU/AMD: Move Zenbleed check to the Zen2 init function")
Cc: <stable@vger.kernel.org>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: John Allen <john.allen@amd.com>
---
v2:
  - Clean up commit description
---
 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 015971adadfc..368344e1394b 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1202,5 +1202,6 @@ void amd_check_microcode(void)
 	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
 		return;
 
-	on_each_cpu(zenbleed_check_cpu, NULL, 1);
+	if (boot_cpu_has(X86_FEATURE_ZEN2))
+		on_each_cpu(zenbleed_check_cpu, NULL, 1);
 }
-- 
2.34.1

[tip: x86/urgent] x86/CPU/AMD: Only apply Zenbleed fix for Zen2 during late microcode load

[tip-bot2 for John Allen]

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

Commit-ID:     ee4d4e8d2c3bec6ee652599ab31991055a72c322
Gitweb:        https://git.kernel.org/tip/ee4d4e8d2c3bec6ee652599ab31991055a72c322
Author:        John Allen <john.allen@amd.com>
AuthorDate:    Mon, 23 Sep 2024 16:44:04 
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Fri, 11 Oct 2024 21:26:45 +02:00

x86/CPU/AMD: Only apply Zenbleed fix for Zen2 during late microcode load

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@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20240923164404.27227-1-john.allen@amd.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 015971a..fab5cae 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -1202,5 +1202,6 @@ 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);
 }