lguest: Fix guest crash when CONFIG_X86_USE_3DNOW=y

One of the very first things lguest_init() does is a memcpy.  On
Athlon/Duron/K7 or CyrixIII/VIA-C3 or Geode GX/LX, this tries to use
MMX.

memcpy -> _mmx_memcpy -> kernel_fpu_begin -> clts -> paravirt_ops.clts

But we haven't set paravirt_ops.clts yet, so we do the native version
and crash.  The simplest solution is to use __memcpy.

Thanks to Michael Rasenberger for the bug report.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/lguest/lguest.c

@@ -964,11 +964,12 @@ __init void lguest_init(void *boot)
 {
 	/* Copy boot parameters first: the Launcher put the physical location
 	 * in %esi, and head.S converted that to a virtual address and handed
-	 * it to us. */
-	memcpy(&boot_params, boot, PARAM_SIZE);
+	 * it to us.  We use "__memcpy" because "memcpy" sometimes tries to do
+	 * tricky things to go faster, and we're not ready for that. */
+	__memcpy(&boot_params, boot, PARAM_SIZE);
 	/* The boot parameters also tell us where the command-line is: save
 	 * that, too. */
-	memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr),
+	__memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr),
 	       COMMAND_LINE_SIZE);
 
 	/* We're under lguest, paravirt is enabled, and we're running at