linux-kernel - [tip:x86/urgent] x86/cpu/AMD: Fix erratum 1076 (CPB bit)

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Message-ID: <tip-f7f3dc00f61261cdc9ccd8b886f21bc4dffd6fd9@git.kernel.org>
Date:   Fri, 15 Sep 2017 02:33:47 -0700
From:   tip-bot for Borislav Petkov <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bp@...e.de, torvalds@...ux-foundation.org, peterz@...radead.org,
        hpa@...or.com, linux-kernel@...r.kernel.org,
        sherry.hurwitz@....com, mingo@...nel.org, tglx@...utronix.de
Subject: [tip:x86/urgent] x86/cpu/AMD: Fix erratum 1076 (CPB bit)

Commit-ID:  f7f3dc00f61261cdc9ccd8b886f21bc4dffd6fd9
Gitweb:     http://git.kernel.org/tip/f7f3dc00f61261cdc9ccd8b886f21bc4dffd6fd9
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Thu, 7 Sep 2017 19:08:21 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 15 Sep 2017 11:30:53 +0200

x86/cpu/AMD: Fix erratum 1076 (CPB bit)

CPUID Fn8000_0007_EDX[CPB] is wrongly 0 on models up to B1. But they do
support CPB (AMD's Core Performance Boosting cpufreq CPU feature), so fix that.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Sherry Hurwitz <sherry.hurwitz@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20170907170821.16021-1-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/cpu/amd.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index 9862e2c..d58184b 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -763,6 +763,16 @@ static void init_amd_bd(struct cpuinfo_x86 *c)
 	}
 }
 
+static void init_amd_zn(struct cpuinfo_x86 *c)
+{
+	/*
+	 * Fix erratum 1076: CPB feature bit not being set in CPUID. It affects
+	 * all up to and including B1.
+	 */
+	if (c->x86_model <= 1 && c->x86_mask <= 1)
+		set_cpu_cap(c, X86_FEATURE_CPB);
+}
+
 static void init_amd(struct cpuinfo_x86 *c)
 {
 	early_init_amd(c);
@@ -791,6 +801,7 @@ static void init_amd(struct cpuinfo_x86 *c)
 	case 0x10: init_amd_gh(c); break;
 	case 0x12: init_amd_ln(c); break;
 	case 0x15: init_amd_bd(c); break;
+	case 0x17: init_amd_zn(c); break;
 	}
 
 	/* Enable workaround for FXSAVE leak */