x86/kvm: Don't enable IRQ when IRQ enabled in kvm_wait

Commit f4e61f0c ("x86/kvm: Fix broken irq restoration in kvm_wait")
replaced "local_irq_restore() when IRQ enabled" with "local_irq_enable()
when IRQ enabled" to suppress a warnning.

Although there is no similar debugging warnning for doing local_irq_enable()
when IRQ enabled as doing local_irq_restore() in the same IRQ situation.  But
doing local_irq_enable() when IRQ enabled is no less broken as doing
local_irq_restore() and we'd better avoid it.

Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20210814035129.154242-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kernel/kvm.c

@@ -884,10 +884,11 @@ static void kvm_wait(u8 *ptr, u8 val)
 	} else {
 		local_irq_disable();
 
+		/* safe_halt() will enable IRQ */
 		if (READ_ONCE(*ptr) == val)
 			safe_halt();
-
-		local_irq_enable();
+		else
+			local_irq_enable();
 	}
 }