evidently a coherence is needed here.  this can only make sense
if there is something very special about executable code with no
context switching.  does anyone know for certain?

Reference: /n/atom/patch/applied/warpcoherence
Date: Sat May 24 19:30:58 CES 2014
Signed-off-by: quanstro@quanstro.net

--- /sys/src/nix/k10/main.c	Sat May 24 19:30:04 2014
+++ /sys/src/nix/k10/main.c	Sat May 24 19:30:04 2014
@@ -351,6 +351,7 @@
 	void (*f)(uintmem, uintmem, usize);
 
 	writeconf();
+	synccons();
 	procwired(up, 0);
 
 	for(i = 1; i < active.nonline; i++)
@@ -358,7 +359,6 @@
 	while((a=active.nonline)>1)
 		monmwait(&active.nonline, a);
 
-	synccons();
 	devtabshutdown();
 	pcireset();
 	splhi();
@@ -376,6 +376,7 @@
 	f = UINT2PTR(REBOOTADDR);
 	memmove(f, rebootcode, sizeof(rebootcode));
 	print("warp32...\n");
+	coherence();		/* necessary */
 	f(PTR2UINT(entry), PADDR(code), size);
 }