2 files changed, 16 insertions, 9 deletions
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4d90dd3a3b3a..eb10895e3eb4 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -269,22 +269,18 @@ static int tsc_aux_uret_slot __read_mostly = -1;
 
 static const u32 msrpm_ranges[] = {0, 0xc0000000, 0xc0010000};
 
-#define NUM_MSR_MAPS ARRAY_SIZE(msrpm_ranges)
-#define MSRS_RANGE_SIZE 2048
-#define MSRS_IN_RANGE (MSRS_RANGE_SIZE * 8 / 2)
-
 u32 svm_msrpm_offset(u32 msr)
 {
 	u32 offset;
 	int i;
 
-	for (i = 0; i < NUM_MSR_MAPS; i++) {
+	for (i = 0; i < ARRAY_SIZE(msrpm_ranges); i++) {
 		if (msr < msrpm_ranges[i] ||
-		    msr >= msrpm_ranges[i] + MSRS_IN_RANGE)
+		    msr >= msrpm_ranges[i] + SVM_MSRS_PER_RANGE)
 			continue;
 
-		offset  = (msr - msrpm_ranges[i]) / 4; /* 4 msrs per u8 */
-		offset += (i * MSRS_RANGE_SIZE);       /* add range offset */
+		offset  = (msr - msrpm_ranges[i]) / SVM_MSRS_PER_BYTE;
+		offset += (i * SVM_MSRPM_BYTES_PER_RANGE);  /* add range offset */
 
 		/* Now we have the u8 offset - but need the u32 offset */
 		return offset / 4;
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index f1e466a10219..086a8c8aae86 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -613,11 +613,22 @@ static inline void svm_vmgexit_no_action(struct vcpu_svm *svm, u64 data)
 	svm_vmgexit_set_return_code(svm, GHCB_HV_RESP_NO_ACTION, data);
 }
 
-/* svm.c */
+/*
+ * The MSRPM is 8KiB in size, divided into four 2KiB ranges (the fourth range
+ * is reserved).  Each MSR within a range is covered by two bits, one each for
+ * read (bit 0) and write (bit 1), where a bit value of '1' means intercepted.
+ */
+#define SVM_MSRPM_BYTES_PER_RANGE 2048
+#define SVM_BITS_PER_MSR 2
+#define SVM_MSRS_PER_BYTE (BITS_PER_BYTE / SVM_BITS_PER_MSR)
+#define SVM_MSRS_PER_RANGE (SVM_MSRPM_BYTES_PER_RANGE * SVM_MSRS_PER_BYTE)
+static_assert(SVM_MSRS_PER_RANGE == 8192);
+
 #define MSR_INVALID				0xffffffffU
 
 #define DEBUGCTL_RESERVED_BITS (~DEBUGCTLMSR_LBR)
 
+/* svm.c */
 extern bool dump_invalid_vmcb;
 
 u32 svm_msrpm_offset(u32 msr);