From: "Scott Parish" <srparish@us.ibm.com>
Subject: [patch] monitor_table is getting set to 0 for domu
	x86_64
Date: Sat, 18 Jun 2005 19:49:11 +0000
Message-ID: <20050618194911.GG2912@us.ibm.com>
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monitor_table is pfn 0 when __context_switch goes to set cr3 for a
second domain.

I hacked update_pagetables to print out what monitor_table gets set
to, here's the output while launching a domu:

  (XEN) guest_table_user: 0x0
  (XEN) shadow_table: 0x0
  (XEN) guest_table: 0x169b
  (XEN) using guest_table_user: 0x0
  ..
  (XEN) cs: monitor_table: 0x0
  (XEN) Domain 1 (vcpu#0) crashed on cpu#0:
  ..

While the attached patch takes care of the problem, and i don't
understand everything i know about TF_kernel_mode and guest_table_user,
so likely a better solution is in order. If somebody wouldn't mind
saying a few words about either of these, i'd appreciate it.

With this patch i can tell that a domU actually makes some progress
(judging from the register state), before falling on its face when it
makes its first syscall.

Huge props to Jerone for pointing out sync_console to me!

sRp

-- 
Scott Parish
Signed-off-by: srparish@us.ibm.com

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--- old-xen-build/xen/include/asm-x86/shadow.h	2005-06-07 13:50:19.000000000 +0000
+++ new-xen-build/xen/include/asm-x86/shadow.h	2005-06-18 20:34:14.000000000 +0000
@@ -1700,7 +1700,8 @@ static inline void update_pagetables(str
     if ( likely(!shadow_mode_external(d)) )
     {
 #ifdef __x86_64__
-        if ( !(v->arch.flags & TF_kernel_mode) )
+        if ( !(v->arch.flags & TF_kernel_mode) &&
+             pagetable_get_pfn(v->arch.guest_table_user) )
             v->arch.monitor_table = v->arch.guest_table_user;
         else
 #endif


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