[Xen-devel] [PATCH v3 2/9] x86/mce_intel: detect and enable LMCE on Intel host

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

Enable LMCE if it's supported by the host CPU. If Xen boot parameter
"mce_fb = 1" is present, LMCE will be disabled forcibly.

Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Changes in v3:
 * Make lmce_support static.
---
 xen/arch/x86/cpu/mcheck/mce_intel.c | 46 ++++++++++++++++++++++++++++++++-----
 xen/arch/x86/cpu/mcheck/x86_mca.h   |  5 ++++
 xen/include/asm-x86/msr-index.h     |  2 ++
 3 files changed, 47 insertions(+), 6 deletions(-)

diff --git a/xen/arch/x86/cpu/mcheck/mce_intel.c 
b/xen/arch/x86/cpu/mcheck/mce_intel.c
index fdf57ce..3c57052 100644
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -29,6 +29,9 @@ boolean_param("mce_fb", mce_force_broadcast);
 
 static int __read_mostly nr_intel_ext_msrs;
 
+/* If mce_force_broadcast == 1, lmce_support will be disabled forcibly. */
+static bool __read_mostly lmce_support;
+
 /* Intel SDM define bit15~bit0 of IA32_MCi_STATUS as the MC error code */
 #define INTEL_MCCOD_MASK 0xFFFF
 
@@ -698,10 +701,34 @@ static bool mce_is_broadcast(struct cpuinfo_x86 *c)
     return false;
 }
 
+static bool intel_enable_lmce(void)
+{
+    uint64_t msr_content;
+
+    /*
+     * Section "Enabling Local Machine Check" in Intel SDM Vol 3
+     * requires software must ensure the LOCK bit and LMCE_ON bit
+     * of MSR_IA32_FEATURE_CONTROL are set before setting
+     * MSR_IA32_MCG_EXT_CTL.LMCE_EN.
+     */
+
+    if ( rdmsr_safe(MSR_IA32_FEATURE_CONTROL, msr_content) )
+        return false;
+
+    if ( (msr_content & IA32_FEATURE_CONTROL_LOCK) &&
+         (msr_content & IA32_FEATURE_CONTROL_LMCE_ON) )
+    {
+        wrmsrl(MSR_IA32_MCG_EXT_CTL, MCG_EXT_CTL_LMCE_EN);
+        return true;
+    }
+
+    return false;
+}
+
 /* Check and init MCA */
 static void intel_init_mca(struct cpuinfo_x86 *c)
 {
-    bool broadcast, cmci = false, ser = false;
+    bool broadcast, cmci = false, ser = false, lmce = false;
     int ext_num = 0, first;
     uint64_t msr_content;
 
@@ -721,33 +748,40 @@ static void intel_init_mca(struct cpuinfo_x86 *c)
 
     first = mce_firstbank(c);
 
+    if (!mce_force_broadcast && (msr_content & MCG_LMCE_P))
+        lmce = intel_enable_lmce();
+
 #define CAP(enabled, name) ((enabled) ? ", " name : "")
     if (smp_processor_id() == 0)
     {
         dprintk(XENLOG_INFO,
-                "MCA capability: firstbank %d, %d ext MSRs%s%s%s\n",
+                "MCA Capability: firstbank %d, extended MCE MSR %d%s%s%s%s\n",
                 first, ext_num,
                 CAP(broadcast, "BCAST"),
                 CAP(ser, "SER"),
-                CAP(cmci, "CMCI"));
+                CAP(cmci, "CMCI"),
+                CAP(lmce, "LMCE"));
 
         mce_broadcast = broadcast;
         cmci_support = cmci;
         ser_support = ser;
+        lmce_support = lmce;
         nr_intel_ext_msrs = ext_num;
         firstbank = first;
     }
     else if (cmci != cmci_support || ser != ser_support ||
              broadcast != mce_broadcast ||
-             first != firstbank || ext_num != nr_intel_ext_msrs)
+             first != firstbank || ext_num != nr_intel_ext_msrs ||
+             lmce != lmce_support)
         dprintk(XENLOG_WARNING,
                 "CPU%u has different MCA capability "
-                "(firstbank %d, %d ext MSRs%s%s%s)"
+                "(firstbank %d, extended MCE MSR %d%s%s%s%s)"
                 " than BSP, may cause undetermined result!!!\n",
                 smp_processor_id(), first, ext_num,
                 CAP(broadcast, "BCAST"),
                 CAP(ser, "SER"),
-                CAP(cmci, "CMCI"));
+                CAP(cmci, "CMCI"),
+                CAP(lmce, "LMCE"));
 #undef CAP
 }
 
diff --git a/xen/arch/x86/cpu/mcheck/x86_mca.h 
b/xen/arch/x86/cpu/mcheck/x86_mca.h
index de03f82..0f87bcf 100644
--- a/xen/arch/x86/cpu/mcheck/x86_mca.h
+++ b/xen/arch/x86/cpu/mcheck/x86_mca.h
@@ -36,6 +36,7 @@
 #define MCG_TES_P               (1ULL<<11) /* Intel specific */
 #define MCG_EXT_CNT             16         /* Intel specific */
 #define MCG_SER_P               (1ULL<<24) /* Intel specific */
+#define MCG_LMCE_P              (1ULL<<27) /* Intel specific */
 /* Other bits are reserved */
 
 /* Bitfield of the MSR_IA32_MCG_STATUS register */
@@ -46,6 +47,10 @@
 /* Bits 3-63 are reserved on CPU not supporting LMCE */
 /* Bits 4-63 are reserved on CPU supporting LMCE */
 
+/* Bitfield of MSR_IA32_MCG_EXT_CTL register (Intel Specific) */
+#define MCG_EXT_CTL_LMCE_EN     (1ULL<<0)
+/* Other bits are reserved */
+
 /* Bitfield of MSR_K8_MCi_STATUS registers */
 /* MCA error code */
 #define MCi_STATUS_MCA          0x000000000000ffffULL
diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
index 771e750..756b23d 100644
--- a/xen/include/asm-x86/msr-index.h
+++ b/xen/include/asm-x86/msr-index.h
@@ -51,6 +51,7 @@
 #define MSR_IA32_MCG_CAP               0x00000179
 #define MSR_IA32_MCG_STATUS            0x0000017a
 #define MSR_IA32_MCG_CTL               0x0000017b
+#define MSR_IA32_MCG_EXT_CTL   0x000004d0
 
 #define MSR_IA32_PEBS_ENABLE           0x000003f1
 #define MSR_IA32_DS_AREA               0x00000600
@@ -296,6 +297,7 @@
 #define IA32_FEATURE_CONTROL_SENTER_PARAM_CTL         0x7f00
 #define IA32_FEATURE_CONTROL_ENABLE_SENTER            0x8000
 #define IA32_FEATURE_CONTROL_SGX_ENABLE               0x40000
+#define IA32_FEATURE_CONTROL_LMCE_ON                  0x100000
 
 #define MSR_IA32_TSC_ADJUST            0x0000003b
 
-- 
2.10.1


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