linux-kernel - [PATCH v3 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo

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Date:   Thu, 15 Sep 2016 16:33:23 -0700
From:   Kyle Huey <me@...ehuey.com>
To:     Robert O'Callahan <robert@...llahan.org>
Cc:     linux-kernel@...r.kernel.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...capital.net>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Borislav Petkov <bp@...e.de>, linux-api@...r.kernel.org,
        xen-devel@...ts.xenproject.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Huang Rui <ray.huang@....com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <len.brown@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Aravind Gopalakrishnan <aravind.gopalakrishnan@....com>,
        Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>
Subject: [PATCH v3 2/3] x86 Test and expose CPUID faulting capabilities in /proc/cpuinfo

Signed-off-by: Kyle Huey <khuey@...ehuey.com>
---
 arch/x86/include/asm/cpufeatures.h |  1 +
 arch/x86/include/asm/msr-index.h   |  1 +
 arch/x86/kernel/cpu/scattered.c    | 14 ++++++++++++++
 3 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 92a8308..78b9d06 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -190,6 +190,7 @@
 
 #define X86_FEATURE_CPB		( 7*32+ 2) /* AMD Core Performance Boost */
 #define X86_FEATURE_EPB		( 7*32+ 3) /* IA32_ENERGY_PERF_BIAS support */
+#define X86_FEATURE_CPUID_FAULT ( 7*32+ 4) /* Intel CPUID faulting */
 
 #define X86_FEATURE_HW_PSTATE	( 7*32+ 8) /* AMD HW-PState */
 #define X86_FEATURE_PROC_FEEDBACK ( 7*32+ 9) /* AMD ProcFeedbackInterface */
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 56f4c66..83908d5 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -41,6 +41,7 @@
 #define MSR_IA32_PERFCTR1		0x000000c2
 #define MSR_FSB_FREQ			0x000000cd
 #define MSR_PLATFORM_INFO		0x000000ce
+#define CPUID_FAULTING_SUPPORT		(1UL << 31)
 
 #define MSR_NHM_SNB_PKG_CST_CFG_CTL	0x000000e2
 #define NHM_C3_AUTO_DEMOTE		(1UL << 25)
diff --git a/arch/x86/kernel/cpu/scattered.c b/arch/x86/kernel/cpu/scattered.c
index 8cb57df..d502da1 100644
--- a/arch/x86/kernel/cpu/scattered.c
+++ b/arch/x86/kernel/cpu/scattered.c
@@ -24,6 +24,17 @@ enum cpuid_regs {
 	CR_EBX
 };
 
+static int supports_cpuid_faulting(void)
+{
+	unsigned int lo, hi;
+
+	if (rdmsr_safe(MSR_PLATFORM_INFO, &lo, &hi) == 0 &&
+	    (lo & CPUID_FAULTING_SUPPORT))
+		return 1;
+	else
+		return 0;
+}
+
 void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 {
 	u32 max_level;
@@ -54,4 +65,7 @@ void init_scattered_cpuid_features(struct cpuinfo_x86 *c)
 		if (regs[cb->reg] & (1 << cb->bit))
 			set_cpu_cap(c, cb->feature);
 	}
+
+	if (supports_cpuid_faulting())
+		set_cpu_cap(c, X86_FEATURE_CPUID_FAULT);
 }
-- 
2.9.3