From: Borislav Petkov <bp@alien8.de>
To: X86 ML <x86@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] x86/CPU/AMD: Rename the spectral chicken
Date: Tue, 25 Apr 2023 21:50:24 +0200 [thread overview]
Message-ID: <20230425195024.17808-1-bp@alien8.de> (raw)
From: "Borislav Petkov (AMD)" <bp@alien8.de>
We've had enough fun with the spectral chicken bit - name it what it
really does: it suppresses non-branch predictions.
Rename defines to make it clear that it is Zen2 only.
No functional changes.
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
arch/x86/include/asm/msr-index.h | 6 ++++--
arch/x86/kernel/cpu/amd.c | 22 +++++++++++-----------
2 files changed, 15 insertions(+), 13 deletions(-)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index ad35355ee43e..0094e6a1b553 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -625,8 +625,10 @@
/* Fam 17h MSRs */
#define MSR_F17H_IRPERF 0xc00000e9
-#define MSR_ZEN2_SPECTRAL_CHICKEN 0xc00110e3
-#define MSR_ZEN2_SPECTRAL_CHICKEN_BIT BIT_ULL(1)
+/* Fam 17h, Zen2 MSRs */
+#define MSR_ZEN2_DE_CFG2 0xc00110e3
+#define MSR_ZEN2_DE_CFG2_SUPPRESS_NOBR_PRED_BIT 1
+#define MSR_ZEN2_DE_CFG2_SUPPRESS_NOBR_PRED BIT(MSR_ZEN2_DE_CFG2_SUPPRESS_NOBR_PRED_BIT)
/* Fam 16h MSRs */
#define MSR_F16H_L2I_PERF_CTL 0xc0010230
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 571abf808ea3..70a41088e900 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -860,23 +860,23 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
clear_rdrand_cpuid_bit(c);
}
-void init_spectral_chicken(struct cpuinfo_x86 *c)
+void init_amd_zn2(struct cpuinfo_x86 *c)
{
#ifdef CONFIG_CPU_UNRET_ENTRY
u64 value;
/*
- * On Zen2 we offer this chicken (bit) on the altar of Speculation.
+ * Suppress speculation from the middle of a basic block, i.e.
+ * non-branch predictions.
*
- * This suppresses speculation from the middle of a basic block, i.e. it
- * suppresses non-branch predictions.
- *
- * We use STIBP as a heuristic to filter out Zen2 from the rest of F17H
+ * STIBP is used as a heuristic to filter out Zen2 from the rest
+ * of family 0x17.
*/
- if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && cpu_has(c, X86_FEATURE_AMD_STIBP)) {
- if (!rdmsrl_safe(MSR_ZEN2_SPECTRAL_CHICKEN, &value)) {
- value |= MSR_ZEN2_SPECTRAL_CHICKEN_BIT;
- wrmsrl_safe(MSR_ZEN2_SPECTRAL_CHICKEN, value);
+ if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
+ cpu_has(c, X86_FEATURE_AMD_STIBP)) {
+ if (!rdmsrl_safe(MSR_ZEN2_DE_CFG2, &value)) {
+ value |= MSR_ZEN2_DE_CFG2_SUPPRESS_NOBR_PRED;
+ wrmsrl_safe(MSR_ZEN2_DE_CFG2, value);
}
}
#endif
@@ -949,7 +949,7 @@ static void init_amd(struct cpuinfo_x86 *c)
case 0x12: init_amd_ln(c); break;
case 0x15: init_amd_bd(c); break;
case 0x16: init_amd_jg(c); break;
- case 0x17: init_spectral_chicken(c);
+ case 0x17: init_amd_zn2(c);
fallthrough;
case 0x19: init_amd_zn(c); break;
}
--
2.35.1
next reply other threads:[~2023-04-25 19:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-25 19:50 Borislav Petkov [this message]
2023-04-25 20:59 ` [PATCH] x86/CPU/AMD: Rename the spectral chicken Peter Zijlstra
2023-04-25 21:15 ` Borislav Petkov
2023-04-26 9:14 ` Thomas Gleixner
2023-04-26 9:21 ` Borislav Petkov
2023-04-26 14:54 ` Andrew Cooper
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