don't double-count maches.  conf.nmach must be accurate and
all maches from 0 ... conf.nmach must be valid for mmuflushes
to not fault.

also, give up if sipi runs out of memory.

Reference: /n/atom/patch/applied2013/acpimaches
Date: Fri Aug 30 21:06:45 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/acpi.c	Fri Aug 30 21:05:13 2013
+++ /sys/src/nix/k10/acpi.c	Fri Aug 30 21:05:13 2013
@@ -527,7 +527,7 @@
 		case 0x00:	/* Processor Local APIC */
 			if(p[4] & Lapicen && conf.nmach < maxmach){
 				lapicinit(p[3], lapicbase, nmach==0);
-				conf.nmach = ++nmach;
+			/*	conf.nmach = */++nmach;
 			}
 			break;
 		case 0x01:	/* I/O APIC */
--- /sys/src/nix/k10/sipi.c	Fri Aug 30 21:05:13 2013
+++ /sys/src/nix/k10/sipi.c	Fri Aug 30 21:05:13 2013
@@ -36,7 +36,7 @@
 	 * The Universal Startup Algorithm described in the MP Spec. 1.4.
 	 * The data needed per-processor is the sum of the stack, page
 	 * table pages, vsvm page and the Mach page. The layout is similar
-	 * to that described in data.h for the bootstrap processor, but
+	 * to that described in dat.h for the bootstrap processor, but
 	 * with any unused space elided.
 	 */
 	nproc = 0;
@@ -56,7 +56,7 @@
 		 */
 		alloc = mallocalign(MACHSTKSZ+4*PTSZ+4*KiB+MACHSZ, 4096, 0, 0);
 		if(alloc == nil)
-			continue;
+			panic("sipi: no memory");
 		p = alloc+MACHSTKSZ;
 
 		sipiptr[-1] = mmuphysaddr(PTR2UINT(p));