# HG changeset patch
# User kaf24@scramble.cl.cam.ac.uk
# Date 1101493299 0
# Node ID a46548db5e52293f155f0c41f5d641ee14093241
# Parent  d0daec09aa8b65976060e491b20702752b257c00
bitkeeper revision 1.1159.187.20 (41a77433rez_BGuifdBbTI3Y34kiag)

Deal with exception from guest context with real interrupts disabled.
This can happen because IOPL != 0 and even a well-behaved guest may
execute random BIOS code if it is a privileged hardware-controlling
domain (e.g., DOM0 X server).


diff -r d0daec09aa8b -r a46548db5e52 xen/arch/x86/x86_32/entry.S
--- a/xen/arch/x86/x86_32/entry.S	Thu Nov 25 22:09:38 2004 +0000
+++ b/xen/arch/x86/x86_32/entry.S	Fri Nov 26 18:21:39 2004 +0000
@@ -339,7 +339,7 @@ error_code:
         SET_XEN_SEGMENTS(a)
         testb $X86_EFLAGS_IF>>8,XREGS_eflags+1(%esp)
         jz    exception_with_ints_disabled
-        sti                             # re-enable interrupts
+1:      sti                             # re-enable interrupts
         xorl  %eax,%eax
         movw  XREGS_entry_vector(%esp),%ax
         movl  %esp,%edx
@@ -354,8 +354,8 @@ error_code:
 
 exception_with_ints_disabled:
         movb  XREGS_cs(%esp),%al
-	testb $3,%al                    # interrupts disabled outside Xen?
-	jnz   FATAL_exception_with_ints_disabled
+	testb $3,%al   # interrupts disabled outside Xen?
+	jnz   1b       # it really does happen! (e.g., DOM0 X server)
         pushl XREGS_eip(%esp)
         call  search_pre_exception_table
         addl  $4,%esp