[Xen-changelog] [xen-unstable] xen: Boot on PAE systems with no EFER MSR.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kfraser@xxxxxxxxxxxxxxxxxxxxx
# Date 1181035739 -3600
# Node ID 0feaf2fc75d3e05f65b840f650166b54d7d5eb8e
# Parent  4f05a587cb6b146e1a24a5a672566ac35de40b71
xen: Boot on PAE systems with no EFER MSR.
Bug tracked down by Stefan Berger.
Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>
---
 xen/arch/x86/boot/trampoline.S |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff -r 4f05a587cb6b -r 0feaf2fc75d3 xen/arch/x86/boot/trampoline.S
--- a/xen/arch/x86/boot/trampoline.S    Tue Jun 05 10:08:09 2007 +0100
+++ b/xen/arch/x86/boot/trampoline.S    Tue Jun 05 10:28:59 2007 +0100
@@ -60,17 +60,20 @@ trampoline_protmode_entry:
 
 #if CONFIG_PAGING_LEVELS != 2
         /* Set up EFER (Extended Feature Enable Register). */
+        mov     SYM_TRAMP_PHYS(cpuid_ext_features),%edi
+        test    $0x20100800,%edi /* SYSCALL/SYSRET, No Execute, Long Mode? */
+        jz      .Lskip_efer
         movl    $MSR_EFER,%ecx
         rdmsr
 #if CONFIG_PAGING_LEVELS == 4
         btsl    $_EFER_LME,%eax /* Long Mode      */
         btsl    $_EFER_SCE,%eax /* SYSCALL/SYSRET */
 #endif
-        mov     SYM_TRAMP_PHYS(cpuid_ext_features),%edi
-        btl     $20,%edi        /* CPUID 0x80000001, EDX[20] */
+        btl     $20,%edi        /* No Execute?    */
         jnc     1f
-        btsl    $_EFER_NX,%eax  /* No-Execute     */
+        btsl    $_EFER_NX,%eax  /* No Execute     */
 1:      wrmsr
+.Lskip_efer:
 #endif
 
         mov     $0x80050033,%eax /* hi-to-lo: PG,AM,WP,NE,ET,MP,PE */

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