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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <172867720706.1442.1034024383169751360.tip-bot2@tip-bot2>
Date: Fri, 11 Oct 2024 20:06:47 -0000
From: "tip-bot2 for John Allen" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: John Allen <john.allen@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
  <stable@...r.kernel.org>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/CPU/AMD: Only apply Zenbleed fix for Zen2
 during late microcode load

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@....com>
AuthorDate:    Mon, 23 Sep 2024 16:44:04 
Committer:     Borislav Petkov (AMD) <bp@...en8.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@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
Cc: <stable@...r.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);
 }