expose the acpi configuration of platform devices like the 8042 kbd.

Reference: /n/atom/patch/applied2013/nixarchcfg
Date: Mon Oct  7 22:58:44 CES 2013
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/dat.h	Mon Oct  7 22:58:13 2013
+++ /sys/src/nix/k10/dat.h	Mon Oct  7 22:58:13 2013
@@ -221,7 +221,7 @@
 
 			uint	copymode;	/* 0 is copy on write, 1 is copy on reference */
 
-			uchar	nolegacyprobe;	/* acpi tells us */
+			uchar	nolegacyprobe;	/* acpi tells us.  all negated in case acpi unavailable */
 			uchar	noi8042kbd;
 			uchar	novga;
 			uchar	nomsi;
--- /sys/src/nix/k10/devarch.c	Mon Oct  7 22:58:13 2013
+++ /sys/src/nix/k10/devarch.c	Mon Oct  7 22:58:13 2013
@@ -376,10 +376,33 @@
 	return readstr(off, a, n, buf);
 }
 
+static long
+archcfgread(Chan*, void *a, long n, vlong off)
+{
+	char buf[512], *p, *e;
+
+	p = buf;
+	e = buf+sizeof buf;
+
+	/* builtin devices may be missing. */
+	p = seprint(p, e, "legacy	%d\n", !sys->nolegacyprobe);
+	p = seprint(p, e, "i8042kbd	%d\n", !sys->noi8042kbd);
+	p = seprint(p, e, "vga	%d\n", !sys->novga);
+	p = seprint(p, e, "msi	%d\n", !sys->nomsi);
+	p = seprint(p, e, "cmos	%d\n", !sys->nocmos);
+
+	p = seprint(p, e, "monitor	%d\n", sys->monitor);
+
+	USED(p);
+
+	return readstr(off, a, n, buf);
+}
+
 void
 archinit(void)
 {
 	addarchfile("cputype", 0444, cputyperead, nil);
+	addarchfile("archcfg", 0444, archcfgread, nil);
 }
 
 void
--- /sys/src/nix/k10/arch.c	Mon Oct  7 22:58:13 2013
+++ /sys/src/nix/k10/arch.c	Mon Oct  7 22:58:13 2013
@@ -60,11 +60,11 @@
 {
 	uvlong t;
 
-	cycles(&t);
-	p->pcycles += t;
-
 	fpuprocsave(p);
 	mmuflushtlb(m->pml4->pa);
+
+	cycles(&t);
+	p->pcycles += t;
 }
 
 static void