Introduce intr_state_t and MI "API" for blocking interrupts.

The fact that disabling/enabling real interrupts is totally MD makes
writing portable code harder, here I propose the following API:

enable_intr(void)		Enables "all" hw interrupts.
disable_intr(void)		Disables "all" hw interrupts.
intr_state_t state_intr(void)	Reads hw interrupts state.
restore_intr(intr_state_t)	Restore hw interrupts state.

I think this should map easily to arm or any other future platform,
intr_state_t should be defined to whatever is convenient to the arch.

Switch crit_rundeferred() to use it, when we port stuff to arm, we
just need to mimick the API.

Author: haesbaert

sys/arch/amd64/include/cpufunc.h

@@ -190,6 +190,7 @@ void	setidt(int idx, /*XXX*/caddr_t func, int typ, int dpl);
 
 
 /* XXXX ought to be in psl.h with spl() functions */
+typedef u_long intr_state_t;
 
 static __inline void
 disable_intr(void)
@@ -218,6 +219,9 @@ write_rflags(u_long ef)
 	__asm volatile("pushq %0; popfq" : : "r" (ef));
 }
 
+#define state_intr read_rflags
+#define restore_intr write_rflags
+
 static __inline u_int64_t
 rdmsr(u_int msr)
 {

sys/kern/kern_crit.c

@@ -87,11 +87,11 @@ crit_rundeferred(void)
 {
 	struct cpu_info *ci = curcpu();
 	int i;
-	long rf;
+	intr_state_t ist;
 
 	KASSERT(CRIT_DEPTH == 0);
 
-	rf = read_rflags(); /* XXX or psl ? */
+	ist = state_intr();
 	disable_intr();
 
 	ci->ci_idepth++;
@@ -104,5 +104,5 @@ crit_rundeferred(void)
 		disable_intr();
 	}
 	ci->ci_idepth--;
-	write_rflags(rf);
+	restore_intr(ist);
 }