x86/apic: KVM: Move apic_find_highest_vector() to a common header

In preparation for using apic_find_highest_vector() in Secure AVIC
guest APIC driver, move it and associated macros to apic.h.

No functional change intended.

Acked-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Link: https://lore.kernel.org/r/20250709033242.267892-11-Neeraj.Upadhyay@amd.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: neerajupadhya

arch/x86/include/asm/apic.h

@@ -503,6 +503,28 @@ static inline bool is_vector_pending(unsigned int vector)
 	return lapic_vector_set_in_irr(vector) || pi_pending_this_cpu(vector);
 }
 
+#define MAX_APIC_VECTOR			256
+#define APIC_VECTORS_PER_REG		32
+
+/*
+ * Vector states are maintained by APIC in 32-bit registers that are
+ * 16 bytes aligned. The status of each vector is kept in a single
+ * bit.
+ */
+static inline int apic_find_highest_vector(void *bitmap)
+{
+	int vec;
+	u32 *reg;
+
+	for (vec = MAX_APIC_VECTOR - APIC_VECTORS_PER_REG; vec >= 0; vec -= APIC_VECTORS_PER_REG) {
+		reg = bitmap + APIC_VECTOR_TO_REG_OFFSET(vec);
+		if (*reg)
+			return __fls(*reg) + vec;
+	}
+
+	return -1;
+}
+
 /*
  * Warm reset vector position:
  */

arch/x86/kvm/lapic.c

@@ -27,6 +27,7 @@
 #include <linux/export.h>
 #include <linux/math64.h>
 #include <linux/slab.h>
+#include <asm/apic.h>
 #include <asm/processor.h>
 #include <asm/mce.h>
 #include <asm/msr.h>
@@ -55,9 +56,6 @@
 /* 14 is the version for Xeon and Pentium 8.4.8*/
 #define APIC_VERSION			0x14UL
 #define LAPIC_MMIO_LENGTH		(1 << 12)
-/* followed define is not in apicdef.h */
-#define MAX_APIC_VECTOR			256
-#define APIC_VECTORS_PER_REG		32
 
 /*
  * Enable local APIC timer advancement (tscdeadline mode only) with adaptive
@@ -616,20 +614,6 @@ static const unsigned int apic_lvt_mask[KVM_APIC_MAX_NR_LVT_ENTRIES] = {
 	[LVT_CMCI] = LVT_MASK | APIC_MODE_MASK
 };
 
-static int apic_find_highest_vector(void *bitmap)
-{
-	int vec;
-	u32 *reg;
-
-	for (vec = MAX_APIC_VECTOR - APIC_VECTORS_PER_REG; vec >= 0; vec -= APIC_VECTORS_PER_REG) {
-		reg = bitmap + APIC_VECTOR_TO_REG_OFFSET(vec);
-		if (*reg)
-			return __fls(*reg) + vec;
-	}
-
-	return -1;
-}
-
 static u8 count_vectors(void *bitmap)
 {
 	int vec;