[PATCH] paravirt: Add startup infrastructure for paravirtualization

1) Each hypervisor writes a probe function to detect whether we are
   running under that hypervisor.  paravirt_probe() registers this
   function.

2) If vmlinux is booted with ring != 0, we call all the probe
   functions (with registers except %esp intact) in link order: the
   winner will not return.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Zachary Amsden <zach@vmware.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/arch/i386/kernel/head.S b/arch/i386/kernel/head.S
index 5b14e95ac8b..edef5084ce1 100644
--- a/arch/i386/kernel/head.S
+++ b/arch/i386/kernel/head.S
@@ -55,6 +55,12 @@
  */
 ENTRY(startup_32)
 
+#ifdef CONFIG_PARAVIRT
+        movl %cs, %eax
+        testl $0x3, %eax
+        jnz startup_paravirt
+#endif
+
 /*
  * Set segments to known values.
  */
@@ -486,6 +492,33 @@ ignore_int:
 #endif
         iret
 
+#ifdef CONFIG_PARAVIRT
+startup_paravirt:
+        cld
+        movl $(init_thread_union+THREAD_SIZE),%esp
+
+        /* We take pains to preserve all the regs. */
+        pushl   %edx
+        pushl   %ecx
+        pushl   %eax
+
+        /* paravirt.o is last in link, and that probe fn never returns */
+        pushl   $__start_paravirtprobe
+1:
+        movl    0(%esp), %eax
+        pushl   (%eax)
+        movl    8(%esp), %eax
+        call    *(%esp)
+        popl    %eax
+
+        movl    4(%esp), %eax
+        movl    8(%esp), %ecx
+        movl    12(%esp), %edx
+
+        addl    $4, (%esp)
+        jmp     1b
+#endif
+
 /*
  * Real beginning of normal "text" segment
  */