[PATCH 4/5] SVM: sync VM-exit perf counters with known VM-exit reasons

[Jan Beulich <jbeulich@xxxxxxxx>]

This has gone out of sync over time, resulting in NPF and XSETBV exits
incrementing the same counter. Introduce a simplistic mechanism to
hopefully keep things in better sync going forward.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
---
Given their large (and growing) number, I wonder whether we shouldn't
fold "SVMexits" and "vmexits". They can't both be active at the same
time.

I wasn't sure about the #ifdef: Using CONFIG_PERF_COUNTERS there would
seem slightly odd next to a construct which specifically abstracts away
this aspect.

--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -2644,6 +2644,10 @@ void svm_vmexit_handler(struct cpu_user_
         goto out;
     }
 
+    /* Note: "+2" to account for VMEXIT_NPF_PERFC. */
+#ifdef SVM_PERF_EXIT_REASON_SIZE
+    BUILD_BUG_ON(SVM_PERF_EXIT_REASON_SIZE != VMEXIT_LAST + 2);
+#endif
     perfc_incra(svmexits, exit_reason);
 
     hvm_maybe_deassert_evtchn_irq();
--- a/xen/include/asm-x86/hvm/svm/vmcb.h
+++ b/xen/include/asm-x86/hvm/svm/vmcb.h
@@ -302,6 +302,7 @@ enum VMEXIT_EXITCODE
     VMEXIT_MWAIT_CONDITIONAL= 140, /* 0x8c */
     VMEXIT_XSETBV           = 141, /* 0x8d */
     VMEXIT_RDPRU            = 142, /* 0x8e */
+#define VMEXIT_LAST VMEXIT_RDPRU
     VMEXIT_NPF              = 1024, /* 0x400, nested paging fault */
     VMEXIT_INVALID          =  -1
 };
--- a/xen/include/asm-x86/perfc_defn.h
+++ b/xen/include/asm-x86/perfc_defn.h
@@ -11,8 +11,8 @@ PERFCOUNTER_ARRAY(exceptions,
 PERFCOUNTER_ARRAY(vmexits,              "vmexits", VMX_PERF_EXIT_REASON_SIZE)
 PERFCOUNTER_ARRAY(cause_vector,         "cause vector", VMX_PERF_VECTOR_SIZE)
 
-#define VMEXIT_NPF_PERFC 141
-#define SVM_PERF_EXIT_REASON_SIZE (1+141)
+#define VMEXIT_NPF_PERFC 143
+#define SVM_PERF_EXIT_REASON_SIZE (VMEXIT_NPF_PERFC + 1)
 PERFCOUNTER_ARRAY(svmexits,             "SVMexits", SVM_PERF_EXIT_REASON_SIZE)
 
 #endif /* CONFIG_HVM */