1 files changed, 18 insertions, 12 deletions

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 07ad628dadb7..6f9fd633c888 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -66,6 +66,7 @@
 #define APIC_DEST_NOSHORT               0x0
 #define APIC_DEST_MASK                  0x800
 #define MAX_APIC_VECTOR                 256
+#define APIC_VECTORS_PER_REG            32
 
 #define VEC_POS(v) ((v) & (32 - 1))
 #define REG_POS(v) (((v) >> 5) << 4)
@@ -208,25 +209,30 @@ static const unsigned int apic_lvt_mask[APIC_LVT_NUM] = {
 
 static int find_highest_vector(void *bitmap)
 {
-        u32 *word = bitmap;
-        int word_offset = MAX_APIC_VECTOR >> 5;
+        int vec;
+        u32 *reg;
 
-        while ((word_offset != 0) && (word[(--word_offset) << 2] == 0))
-                continue;
+        for (vec = MAX_APIC_VECTOR - APIC_VECTORS_PER_REG;
+             vec >= 0; vec -= APIC_VECTORS_PER_REG) {
+                reg = bitmap + REG_POS(vec);
+                if (*reg)
+                        return fls(*reg) - 1 + vec;
+        }
 
-        if (likely(!word_offset && !word[0]))
-                return -1;
-        else
-                return fls(word[word_offset << 2]) - 1 + (word_offset << 5);
+        return -1;
 }
 
 static u8 count_vectors(void *bitmap)
 {
-        u32 *word = bitmap;
-        int word_offset;
+        int vec;
+        u32 *reg;
         u8 count = 0;
-        for (word_offset = 0; word_offset < MAX_APIC_VECTOR >> 5; ++word_offset)
-                count += hweight32(word[word_offset << 2]);
+
+        for (vec = 0; vec < MAX_APIC_VECTOR; vec += APIC_VECTORS_PER_REG) {
+                reg = bitmap + REG_POS(vec);
+                count += hweight32(*reg);
+        }
+
         return count;
 }