[PATCH] x86: amend 'n' debug-key output with SMI count

[Jan Beulich <jbeulich@xxxxxxxx>]

... if available only, of course.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -406,9 +406,15 @@ void __init early_cpu_init(bool verbose)
                paddr_bits -= (ebx >> 6) & 0x3f;
        }
 
-       if (!(c->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON)))
+       if (!(c->x86_vendor & (X86_VENDOR_AMD | X86_VENDOR_HYGON))) {
+               uint64_t smi_count;
+
                park_offline_cpus = opt_mce;
 
+               if (!verbose && !rdmsr_safe(MSR_SMI_COUNT, smi_count))
+                       setup_force_cpu_cap(X86_FEATURE_SMI_COUNT);
+       }
+
        initialize_cpu_data(0);
 }
 
--- a/xen/arch/x86/include/asm/cpufeatures.h
+++ b/xen/arch/x86/include/asm/cpufeatures.h
@@ -24,7 +24,7 @@ XEN_CPUFEATURE(APERFMPERF,        X86_SY
 XEN_CPUFEATURE(MFENCE_RDTSC,      X86_SYNTH( 9)) /* MFENCE synchronizes RDTSC 
*/
 XEN_CPUFEATURE(XEN_SMEP,          X86_SYNTH(10)) /* SMEP gets used by Xen 
itself */
 XEN_CPUFEATURE(XEN_SMAP,          X86_SYNTH(11)) /* SMAP gets used by Xen 
itself */
-/* Bit 12 unused. */
+XEN_CPUFEATURE(SMI_COUNT,         X86_SYNTH(12)) /* MSR_SMI_COUNT exists */
 XEN_CPUFEATURE(IND_THUNK_LFENCE,  X86_SYNTH(13)) /* Use IND_THUNK_LFENCE */
 XEN_CPUFEATURE(IND_THUNK_JMP,     X86_SYNTH(14)) /* Use IND_THUNK_JMP */
 XEN_CPUFEATURE(SC_NO_BRANCH_HARDEN, X86_SYNTH(15)) /* (Disable) Conditional 
branch hardening */
--- a/xen/arch/x86/include/asm/msr-index.h
+++ b/xen/arch/x86/include/asm/msr-index.h
@@ -28,6 +28,8 @@
 #define  TEST_CTRL_SPLITLOCK_DETECT         (_AC(1, ULL) << 29)
 #define  TEST_CTRL_SPLITLOCK_DISABLE        (_AC(1, ULL) << 31)
 
+#define MSR_SMI_COUNT                       0x00000034
+
 #define MSR_INTEL_CORE_THREAD_COUNT         0x00000035
 #define  MSR_CTC_THREAD_MASK                0x0000ffff
 #define  MSR_CTC_CORE_MASK                  _AC(0xffff0000, U)
--- a/xen/arch/x86/nmi.c
+++ b/xen/arch/x86/nmi.c
@@ -589,9 +589,20 @@ static void cf_check do_nmi_stats(unsign
     unsigned int cpu;
     bool pend, mask;
 
-    printk("CPU\tNMI\n");
+    printk("CPU\tNMI%s\n", boot_cpu_has(X86_FEATURE_SMI_COUNT) ? "\tSMI" : "");
     for_each_online_cpu ( cpu )
-        printk("%3u\t%3u\n", cpu, per_cpu(nmi_count, cpu));
+    {
+        printk("%3u\t%3u", cpu, per_cpu(nmi_count, cpu));
+        if ( boot_cpu_has(X86_FEATURE_SMI_COUNT) )
+        {
+            unsigned int smi_count, dummy;
+
+            rdmsr(MSR_SMI_COUNT, smi_count, dummy);
+            printk("\t%3u\n", smi_count);
+        }
+        else
+            printk("\n");
+    }
 
     if ( !hardware_domain || !(v = domain_vcpu(hardware_domain, 0)) )
         return;