linux-kernel - [PATCH 4.9 07/31] x86/cpu: Add a helper function x86_read_arch_cap

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Message-Id: <20191115062012.261664141@linuxfoundation.org>
Date:   Fri, 15 Nov 2019 14:20:36 +0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Neelima Krishnan <neelima.krishnan@...el.com>,
        Mark Gross <mgross@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 4.9 07/31] x86/cpu: Add a helper function x86_read_arch_cap_msr()

From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>

commit 286836a70433fb64131d2590f4bf512097c255e1 upstream.

Add a helper function to read the IA32_ARCH_CAPABILITIES MSR.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Neelima Krishnan <neelima.krishnan@...el.com>
Reviewed-by: Mark Gross <mgross@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/kernel/cpu/common.c |   15 +++++++++++----
 arch/x86/kernel/cpu/cpu.h    |    2 ++
 2 files changed, 13 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -962,19 +962,26 @@ static bool __init cpu_matches(unsigned
 	return m && !!(m->driver_data & which);
 }
 
-static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
+u64 x86_read_arch_cap_msr(void)
 {
 	u64 ia32_cap = 0;
 
+	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
+		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
+
+	return ia32_cap;
+}
+
+static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
+{
+	u64 ia32_cap = x86_read_arch_cap_msr();
+
 	if (cpu_matches(NO_SPECULATION))
 		return;
 
 	setup_force_cpu_bug(X86_BUG_SPECTRE_V1);
 	setup_force_cpu_bug(X86_BUG_SPECTRE_V2);
 
-	if (cpu_has(c, X86_FEATURE_ARCH_CAPABILITIES))
-		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, ia32_cap);
-
 	if (!cpu_matches(NO_SSB) && !(ia32_cap & ARCH_CAP_SSB_NO) &&
 	   !cpu_has(c, X86_FEATURE_AMD_SSB_NO))
 		setup_force_cpu_bug(X86_BUG_SPEC_STORE_BYPASS);
--- a/arch/x86/kernel/cpu/cpu.h
+++ b/arch/x86/kernel/cpu/cpu.h
@@ -51,4 +51,6 @@ extern int detect_ht_early(struct cpuinf
 
 extern void x86_spec_ctrl_setup_ap(void);
 
+extern u64 x86_read_arch_cap_msr(void);
+
 #endif /* ARCH_X86_CPU_H */