[MODERATED] [PATCH 2/9] TAA 2

From: Pawan Gupta <[email protected]>
Subject: [PATCH 2/9] x86/cpu: Add a helper function x86_read_arch_cap_msr()

Add a helper function to read the IA32_ARCH_CAPABILITIES MSR.

Signed-off-by: Pawan Gupta <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Mark Gross <[email protected]>
Reviewed-by: Tony Luck <[email protected]>
Tested-by: Neelima Krishnan <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: x86-ml <[email protected]>
---
 arch/x86/kernel/cpu/common.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9ae7d1bcd4f4..897c8302d982 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1092,19 +1092,26 @@ static bool __init cpu_matches(unsigned long which)
 	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);
-- 
2.21.0