1.  no isr is required for the lapic.  (and the old code was wrong anyway).  don't do it.
this saves ~100 cycles/clock interrupt.  we're now down to ~980 from 1380 just a few days
ago.

2.  properly account for rdts in ioapics.  panic if the count is off.  don't call ioapicintrdisable
for msi interrupts.

Reference: /n/atom/patch/applied/lapicnoisr
Date: Fri Jan  3 03:59:51 CET 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/lapic.c	Fri Jan  3 03:57:51 2014
+++ /sys/src/nix/k10/lapic.c	Fri Jan  3 03:57:51 2014
@@ -108,16 +108,6 @@
 	return vecno;
 }
 
-int
-lapicisr(int vecno)
-{
-	int isr;
-
-	isr = lapicrget(Is + (vecno/32)*16);
-
-	return isr & (1<<(vecno%32));
-}
-
 static char*
 lapicprint(char *p, char *e, Lapic *a, int i)
 {
--- /sys/src/nix/k10/apic.h	Fri Jan  3 03:57:51 2014
+++ /sys/src/nix/k10/apic.h	Fri Jan  3 03:57:51 2014
@@ -84,6 +84,8 @@
 int	gsitoapicid(int, uint*);
 void	ioapicdump(void);
 Apic*	ioapicinit(int, int, uintmem);
+int	ioapicintrdisable(int);
+int	ioapicintrenable(Vctl*);
 void	ioapicintrinit(int, int, int, int, int, u32int);
 Apic*	ioapiclookup(uint);
 void	ioapiconline(void);
@@ -91,7 +93,6 @@
 int	lapiceoi(int);
 void	lapicinit(int, uintmem, int);
 void	lapicipi(int);
-int	lapicisr(int);
 Apic*	lapiclookup(uint);
 int	lapiconline(void);
 void	lapicpri(int);
--- /sys/src/nix/k10/trap.c	Fri Jan  3 03:57:51 2014
+++ /sys/src/nix/k10/trap.c	Fri Jan  3 03:57:51 2014
@@ -101,7 +101,6 @@
 intrdisable(void* vector)
 {
 	Vctl *v, *x, **ll;
-	extern int ioapicintrdisable(int);
 
 	ilock(&vctllock);
 	v = vector;
@@ -116,7 +115,10 @@
 		v->mask(v, 1);
 	v->f(nil, v->a);
 	*ll = v->next;
-	ioapicintrdisable(v->vno);		/* BOTCH: this is wrong for non-ioapic interrupts shoid msi disable*/
+	if(strcmp(v->type, "ioapic") == 0)
+		ioapicintrdisable(v->vno);
+	else
+		iprint("intrdisable: not disabling %s type %s\n", v->name, v->type);
 	iunlock(&vctllock);
 
 	free(v);
--- /sys/src/nix/k10/ioapic.c	Fri Jan  3 03:57:51 2014
+++ /sys/src/nix/k10/ioapic.c	Fri Jan  3 03:57:51 2014
@@ -421,6 +421,8 @@
 	/* Set delivery mode (lo) and destination field (hi) */
 	*hi = mach->apicno<<24;
 	*lo |= v->vno|Pm|MTf;
+	if(*lo & Lm)
+		*lo |= MTlp;
 	return 0;
 }
 
@@ -444,18 +446,14 @@
 	lo = IPlow | TMedge;
 	ioapicphysdd(v, &hi, &lo);
 
-	if(lo & Lm)
-		lo |= MTlp;
-
 	msivec = (u64int)hi<<32 | lo;
 	if(pcimsienable(p, msivec) == -1)
 		return -1;
-	v->isr = lapicisr;
 	v->eoi = lapiceoi;
 	v->type = "msi";
 	v->mask = msimask;
 
-	DBG("msiirq: %T: enabling %.16llux %s irq %d vno %d\n", p->tbdf, msivec, v->name, v->irq, v->vno);
+	DBG("msiirq: %T: enabling %.16llux %s vno %d\n", p->tbdf, msivec, v->name, v->vno);
 	return v->vno;
 }
 
@@ -470,6 +468,7 @@
 int
 ioapicintrenable(Vctl* v)
 {
+	Pcidev *p;
 	Rbus *rbus;
 	Rdt *rdt;
 	u32int hi, lo;
@@ -496,19 +495,13 @@
 		}
 	}
 	else if((bustype = BUSTYPE(v->tbdf)) == BusPCI){
-		/*
-		 * PCI.
-		 * Make a devno from BUSDNO(tbdf) and pcidev->intp.
-		 */
-		Pcidev *pcidev;
-
 		busno = BUSBNO(v->tbdf);
-		if((pcidev = pcimatchtbdf(v->tbdf)) == nil)
-			panic("no PCI dev for tbdf %T", v->tbdf);
-		if(intrenablemsi(v, pcidev) != -1)
+		if((p = pcimatchtbdf(v->tbdf)) == nil)
+			panic("ioapic: no pci dev for tbdf %T", v->tbdf);
+		if(intrenablemsi(v, p) != -1)
 			return v->vno;
-		disablemsi(v, pcidev);
-		if((devno = pcicfgr8(pcidev, PciINTP)) == 0)
+		disablemsi(v, p);
+		if((devno = pcicfgr8(p, PciINTP)) == 0)
 			panic("no INTP for tbdf %T", v->tbdf);
 		devno = BUSDNO(v->tbdf)<<2|(devno-1);
 		DBG("ioapicintrenable: tbdf %T busno %d devno %d\n",
@@ -551,10 +544,10 @@
 	 * the whole IOAPIC to initialise the RDT entry
 	 * rather than putting a Lock in each entry.
 	 */
-	lock(rdt->apic);
 	DBG("%T: %ld/%d/%d (%d)\n", v->tbdf, rdt->apic - xioapic, rbus->devno, rdt->intin, devno);
 
-	rdt->enabled++;
+	lock(rdt->apic);
+	ainc(&rdt->enabled);
 	lo = (rdt->lo & ~Im);
 	ioapicphysdd(v, &hi, &lo);
 
@@ -569,7 +562,6 @@
 
 	DBG("busno %d devno %d hi %#.8ux lo %#.8ux vecno %d\n",
 		busno, devno, hi, lo, v->vno);
-	v->isr = lapicisr;
 	v->eoi = lapiceoi;
 	v->type = "ioapic";
 
@@ -581,26 +573,13 @@
 {
 	Rdt *rdt;
 
-	/*
-	 * FOV. Oh dear. This isn't very good.
-	 * Fortunately rdtvecno[vecno] is static
-	 * once assigned.
-	 * Must do better.
-	 *
-	 * What about any pending interrupts?
-	 */
-	if(vecno < 0 || vecno > MaxVectorAPIC){
-		panic("ioapicintrdisable: vecno %d out of range", vecno);
-		return -1;
-	}
 	if((rdt = rdtvecno[vecno]) == nil){
 		panic("ioapicintrdisable: vecno %d has no rdt", vecno);
 		return -1;
 	}
 
 	lock(rdt->apic);
-	rdt->enabled--;
-	if(rdt->enabled == 0)
+	if(adec(&rdt->enabled) == 0)
 		rtblput(rdt->apic, rdt->intin, 0, rdt->lo);
 	unlock(rdt->apic);