linux-kernel - [PATCH 3.16 04/25] x86/cpu: Add a helper function x86_read_arch_cap

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Date:   Tue, 12 Nov 2019 23:48:01 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Mark Gross" <mgross@...ux.intel.com>,
        "Borislav Petkov" <bp@...e.de>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Neelima Krishnan" <neelima.krishnan@...el.com>,
        "Josh Poimboeuf" <jpoimboe@...hat.com>,
        "Pawan Gupta" <pawan.kumar.gupta@...ux.intel.com>,
        "Tony Luck" <tony.luck@...el.com>
Subject: [PATCH 3.16 04/25] x86/cpu: Add a helper function x86_read_arch_cap_msr()

3.16.77-rc1 review patch.  If anyone has any objections, please let me know.

------------------

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>
---
 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
@@ -878,19 +878,26 @@ 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
@@ -48,4 +48,6 @@ extern void cpu_detect_cache_sizes(struc
  
 extern void x86_spec_ctrl_setup_ap(void);
 
+extern u64 x86_read_arch_cap_msr(void);
+
 #endif /* ARCH_X86_CPU_H */