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Message-ID: <176795997185.510.4581421302854856357.tip-bot2@tip-bot2>
Date: Fri, 09 Jan 2026 11:59:31 -0000
From: "tip-bot2 for Borislav Petkov (AMD)" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Borislav Petkov (AMD)" <bp@...en8.de>,
Nikolay Borisov <nik.borisov@...e.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/cleanups] x86/CPU/AMD: Simplify the spectral chicken fix
The following commit has been merged into the x86/cleanups branch of tip:
Commit-ID: 736a2dcfdae72483a36793bc92182f33bd61d30e
Gitweb: https://git.kernel.org/tip/736a2dcfdae72483a36793bc92182f33bd61d30e
Author: Borislav Petkov (AMD) <bp@...en8.de>
AuthorDate: Tue, 30 Dec 2025 12:07:31 +01:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 09 Jan 2026 11:36:52 +01:00
x86/CPU/AMD: Simplify the spectral chicken fix
msr_set_bit() takes a bit number to set but MSR_ZEN2_SPECTRAL_CHICKEN_BIT
is a bit mask. The usual pattern that code uses is a _BIT-named type
macro instead of a mask.
So convert it to a bit number to reflect that.
Also, msr_set_bit() already does the reading and checking whether the
bit needs to be set so use that instead of a local variable.
Fixup tabbing while at it.
No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@...e.com>
Link: https://patch.msgid.link/20251230110731.28108-1-bp@kernel.org
---
arch/x86/include/asm/msr-index.h | 4 ++--
arch/x86/kernel/cpu/amd.c | 10 ++--------
tools/arch/x86/include/asm/msr-index.h | 4 ++--
3 files changed, 6 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3d0a095..43adc38 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -794,8 +794,8 @@
#define MSR_F19H_UMC_PERF_CTR 0xc0010801
/* Zen 2 */
-#define MSR_ZEN2_SPECTRAL_CHICKEN 0xc00110e3
-#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT BIT_ULL(1)
+#define MSR_ZEN2_SPECTRAL_CHICKEN 0xc00110e3
+#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT 1
/* Fam 17h MSRs */
#define MSR_F17H_IRPERF 0xc00000e9
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index bc94ff1..ab9158c 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -900,20 +900,14 @@ static void fix_erratum_1386(struct cpuinfo_x86 *c)
void init_spectral_chicken(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_MITIGATION_UNRET_ENTRY
- u64 value;
-
/*
* On Zen2 we offer this chicken (bit) on the altar of Speculation.
*
* This suppresses speculation from the middle of a basic block, i.e. it
* suppresses non-branch predictions.
*/
- if (!cpu_has(c, X86_FEATURE_HYPERVISOR)) {
- if (!rdmsrq_safe(MSR_ZEN2_SPECTRAL_CHICKEN, &value)) {
- value |= MSR_ZEN2_SPECTRAL_CHICKEN_BIT;
- wrmsrq_safe(MSR_ZEN2_SPECTRAL_CHICKEN, value);
- }
- }
+ if (!cpu_has(c, X86_FEATURE_HYPERVISOR))
+ msr_set_bit(MSR_ZEN2_SPECTRAL_CHICKEN, MSR_ZEN2_SPECTRAL_CHICKEN_BIT);
#endif
}
diff --git a/tools/arch/x86/include/asm/msr-index.h b/tools/arch/x86/include/asm/msr-index.h
index 9e1720d..d4137a3 100644
--- a/tools/arch/x86/include/asm/msr-index.h
+++ b/tools/arch/x86/include/asm/msr-index.h
@@ -770,8 +770,8 @@
#define MSR_F19H_UMC_PERF_CTR 0xc0010801
/* Zen 2 */
-#define MSR_ZEN2_SPECTRAL_CHICKEN 0xc00110e3
-#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT BIT_ULL(1)
+#define MSR_ZEN2_SPECTRAL_CHICKEN 0xc00110e3
+#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT 1
/* Fam 17h MSRs */
#define MSR_F17H_IRPERF 0xc00000e9
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