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From:   Fenghua Yu <fenghua.yu@intel.com>
To:     "Thomas Gleixner" <tglx@linutronix.de>,
        "Ingo Molnar" <mingo@redhat.com>, "Borislav Petkov" <bp@alien8.de>,
        "H Peter Anvin" <hpa@zytor.com>,
        "Peter Zijlstra" <peterz@infradead.org>,
        "Tony Luck" <tony.luck@intel.com>,
        "Ashok Raj" <ashok.raj@intel.com>,
        "Ravi V Shankar" <ravi.v.shankar@intel.com>
Cc:     "linux-kernel" <linux-kernel@vger.kernel.org>,
        "x86" <x86@kernel.org>, Fenghua Yu <fenghua.yu@intel.com>
Subject: [PATCH v10 4/6] x86/split_lock: Enumerate split lock detection if the IA32_CORE_CAPABILITIES MSR is not supported
Date:   Wed, 20 Nov 2019 16:53:21 -0800
Message-Id: <1574297603-198156-5-git-send-email-fenghua.yu@intel.com>
In-Reply-To: <1574297603-198156-1-git-send-email-fenghua.yu@intel.com>
References: <1574297603-198156-1-git-send-email-fenghua.yu@intel.com>
Sender: linux-kernel-owner@vger.kernel.org
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Architecturally the split lock detection feature is enumerated by
IA32_CORE_CAPABILITIES MSR and future CPU models will indicate presence
of the feature by setting bit 5. But the feature is present in a few
older models where split lock detection is enumerated by the CPU models.

Use a "x86_cpu_id" table to list the older CPU models with the feature.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/intel.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index ce87e2c68767..2614616fb6d3 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -19,6 +19,7 @@
 #include <asm/microcode_intel.h>
 #include <asm/hwcap2.h>
 #include <asm/elf.h>
+#include <asm/cpu_device_id.h>
 
 #ifdef CONFIG_X86_64
 #include <linux/topology.h>
@@ -1034,15 +1035,31 @@ static void __init split_lock_setup(void)
 	setup_force_cpu_cap(X86_FEATURE_SPLIT_LOCK_DETECT);
 }
 
+#define SPLIT_LOCK_CPU(model) {X86_VENDOR_INTEL, 6, model, X86_FEATURE_ANY}
+
+/*
+ * The following processors have split lock detection feature. But since they
+ * don't have MSR IA32_CORE_CAPABILITIES, the feature cannot be enumerated by
+ * the MSR. So enumerate the feature by family and model on these processors.
+ */
+static const struct x86_cpu_id split_lock_cpu_ids[] __initconst = {
+	SPLIT_LOCK_CPU(INTEL_FAM6_ICELAKE_X),
+	SPLIT_LOCK_CPU(INTEL_FAM6_ICELAKE_L),
+	{}
+};
+
 void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c)
 {
 	u64 ia32_core_caps = 0;
 
-	if (!cpu_has(c, X86_FEATURE_CORE_CAPABILITIES))
-		return;
-
-	/* Enumerate features reported in IA32_CORE_CAPABILITIES MSR. */
-	rdmsrl(MSR_IA32_CORE_CAPABILITIES, ia32_core_caps);
+	if (cpu_has(c, X86_FEATURE_CORE_CAPABILITIES)) {
+		/* Enumerate features reported in IA32_CORE_CAPABILITIES MSR. */
+		rdmsrl(MSR_IA32_CORE_CAPABILITIES, ia32_core_caps);
+	} else {
+		/* Enumerate split lock detection by family and model. */
+		if (x86_match_cpu(split_lock_cpu_ids))
+			ia32_core_caps |= MSR_IA32_CORE_CAPABILITIES_SPLIT_LOCK_DETECT;
+	}
 
 	if (ia32_core_caps & MSR_IA32_CORE_CAPABILITIES_SPLIT_LOCK_DETECT)
 		split_lock_setup();
-- 
2.19.1