x86/entry: Use run_sysvec_on_irqstack_cond() for XEN upcall

To avoid yet another macro implementation reuse the existing
run_sysvec_on_irqstack_cond() and move the set_irq_regs() handling into the
called function. Makes the code even simpler.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20210210002512.869753106@linutronix.de

arch/x86/entry/common.c

@@ -245,30 +245,23 @@ static __always_inline bool get_and_clear_inhcall(void) { return false; }
 static __always_inline void restore_inhcall(bool inhcall) { }
 #endif
 
-static void __xen_pv_evtchn_do_upcall(void)
+static void __xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 {
-	irq_enter_rcu();
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
 	inc_irq_stat(irq_hv_callback_count);
 
 	xen_hvm_evtchn_do_upcall();
 
-	irq_exit_rcu();
+	set_irq_regs(old_regs);
 }
 
 __visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
 {
-	struct pt_regs *old_regs;
+	irqentry_state_t state = irqentry_enter(regs);
 	bool inhcall;
-	irqentry_state_t state;
 
-	state = irqentry_enter(regs);
-	old_regs = set_irq_regs(regs);
-
-	instrumentation_begin();
-	run_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs);
-	instrumentation_end();
-
-	set_irq_regs(old_regs);
+	run_sysvec_on_irqstack_cond(__xen_pv_evtchn_do_upcall, regs);
 
 	inhcall = get_and_clear_inhcall();
 	if (inhcall && !WARN_ON_ONCE(state.exit_rcu)) {