[MODERATED] [PATCH v5 02/11] TAAv5 2

From: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
To: speck@linutronix.de
Subject: [MODERATED] [PATCH v5 02/11] TAAv5 2
Date: Fri, 4 Oct 2019 23:27:31 -0700	[thread overview]
Message-ID: <=?utf-8?q?=3Ce6fbe7bb3310c7bd6603af8dc80409425d7ef759=2E157025?= =?utf-8?q?5065=2Egit=2Epawan=2Ekumar=2Egupta=40linux=2Eintel=2Ecom=3E?=> (raw)
In-Reply-To: <cover.1570255065.git.pawan.kumar.gupta@linux.intel.com>

Move IA32_ARCH_CAPABILITIES MSR read to a helper function. If the CPU
doesn't support this MSR return 0. Use this function in following
commits to read IA32_ARCH_CAPABILITIES MSR.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Reviewed-by: Mark Gross <mgross@linux.intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Tested-by: Neelima Krishnan <neelima.krishnan@intel.com>
---
 arch/x86/kernel/cpu/common.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index f125bf7ecb6f..af9e357b2ca9 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1091,19 +1091,27 @@ 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 read_ia32_arch_cap(void)
 {
 	u64 ia32_cap = 0;
 
+	/* Leave the MSR set to all 0's when not supported */
+	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 = read_ia32_arch_cap();
+
 	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);
-- 
2.20.1
