x86/apic: Inline __x2apic_send_IPI_dest()

Avoid one call/ret in networking RPS/RFS fast path, with no space cost.

scripts/bloat-o-meter -t vmlinux.before vmlinux.after
add/remove: 0/2 grow/shrink: 2/0 up/down: 96/-97 (-1)
Function                                     old     new   delta
x2apic_send_IPI                              146     198     +52
__x2apic_send_IPI_mask                       326     370     +44
__pfx___x2apic_send_IPI_dest                  16       -     -16
__x2apic_send_IPI_dest                        81       -     -81
Total: Before=20861234, After=20861233, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20251223052026.4141498-1-edumazet@google.com

Author: edumazet

arch/x86/kernel/apic/local.h

@@ -14,7 +14,6 @@
 #include <asm/apic.h>
 
 /* X2APIC */
-void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest);
 u32 x2apic_get_apic_id(u32 id);
 
 void x2apic_send_IPI_all(int vector);
@@ -42,6 +41,15 @@ static inline unsigned int __prepare_ICR(unsigned int shortcut, int vector,
 	return icr;
 }
 
+#ifdef CONFIG_X86_X2APIC
+static inline void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest)
+{
+	unsigned long cfg = __prepare_ICR(0, vector, dest);
+
+	native_x2apic_icr_write(cfg, apicid);
+}
+#endif
+
 void default_init_apic_ldr(void);
 
 void apic_mem_wait_icr_idle(void);

arch/x86/kernel/apic/x2apic_phys.c

@@ -107,12 +107,6 @@ void x2apic_send_IPI_self(int vector)
 	apic_write(APIC_SELF_IPI, vector);
 }
 
-void __x2apic_send_IPI_dest(unsigned int apicid, int vector, unsigned int dest)
-{
-	unsigned long cfg = __prepare_ICR(0, vector, dest);
-	native_x2apic_icr_write(cfg, apicid);
-}
-
 static int x2apic_phys_probe(void)
 {
 	if (!x2apic_mode)