[Xen-changelog] [xen-unstable] hvm: Fix lmsw handling

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

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1214580059 -3600
# Node ID 6b06639011744b6e22915fc1f97237a574e9305f
# Parent  baaea9f0db5eb153de5bb89e09f084a98e28ae99
hvm: Fix lmsw handling

The lmsw instruction can be used to set CR0_PE, but can never clear
it, once set.

Signed-off-by: Trolle Selander <trolle.selander@xxxxxxxxxxxxx>
---
 xen/arch/x86/hvm/vmx/vmx.c             |    3 ++-
 xen/arch/x86/x86_emulate/x86_emulate.c |    2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff -r baaea9f0db5e -r 6b0663901174 xen/arch/x86/hvm/vmx/vmx.c
--- a/xen/arch/x86/hvm/vmx/vmx.c        Fri Jun 27 16:16:47 2008 +0100
+++ b/xen/arch/x86/hvm/vmx/vmx.c        Fri Jun 27 16:20:59 2008 +0100
@@ -1523,7 +1523,8 @@ static int vmx_cr_access(unsigned long e
         break;
     case VMX_CONTROL_REG_ACCESS_TYPE_LMSW:
         value = v->arch.hvm_vcpu.guest_cr[0];
-        value = (value & ~0xFFFF) | ((exit_qualification >> 16) & 0xFFFF);
+        /* NB. LMSW can set, but never clear, PE. */
+        value = (value & 0xFFFF0001) | ((exit_qualification >> 16) & 0xFFFF);
         HVMTRACE_LONG_1D(LMSW, current, value);
         return !hvm_set_cr0(value);
     default:
diff -r baaea9f0db5e -r 6b0663901174 xen/arch/x86/x86_emulate/x86_emulate.c
--- a/xen/arch/x86/x86_emulate/x86_emulate.c    Fri Jun 27 16:16:47 2008 +0100
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c    Fri Jun 27 16:20:59 2008 +0100
@@ -3284,7 +3284,7 @@ x86_emulate(
             else if ( (rc = ops->read(ea.mem.seg, ea.mem.off,
                                       &cr0w, 2, ctxt)) )
                 goto done;
-            cr0 &= 0xffff0000;
+            cr0 &= 0xffff0001; /* lmsw can set, but never clear, PE */
             cr0 |= (uint16_t)cr0w;
             if ( (rc = ops->write_cr(0, cr0, ctxt)) )
                 goto done;

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