[Xen-changelog] Modify CR0 access emulation -- return physical CR0 (except

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

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID 829517be689f95d3d935ab1af17d0c31ee4950fc
# Parent  87e5ac90a8df30da6e76be4e93d0f67de6f98f80
Modify CR0 access emulation -- return physical CR0 (except
for TS) and allow only the same physical flags to be written
back to CR0 by a guest.

Add write-to-CR4 emulation, but check that the write does not
modify any CR4 flags.

Signed-off-by: Keir Fraser <keir@xxxxxxxxxxxxx>

diff -r 87e5ac90a8df -r 829517be689f xen/arch/x86/traps.c
--- a/xen/arch/x86/traps.c      Fri Dec 23 09:12:41 2005
+++ b/xen/arch/x86/traps.c      Fri Dec 23 15:42:46 2005
@@ -885,7 +885,8 @@
         switch ( modrm_reg )
         {
         case 0: /* Read CR0 */
-            *reg = v->arch.guest_context.ctrlreg[0];
+            *reg = (read_cr0() & ~X86_CR0_TS) |
+                v->arch.guest_context.ctrlreg[0];
             break;
 
         case 2: /* Read CR2 */
@@ -927,6 +928,11 @@
         switch ( modrm_reg )
         {
         case 0: /* Write CR0 */
+            if ( (*reg ^ read_cr0()) & ~X86_CR0_TS )
+            {
+                DPRINTK("Attempt to change unmodifiable CR0 flags.\n");
+                goto fail;
+            }
             (void)do_fpu_taskswitch(!!(*reg & X86_CR0_TS));
             break;
 
@@ -939,6 +945,14 @@
             LOCK_BIGLOCK(v->domain);
             (void)new_guest_cr3(*reg);
             UNLOCK_BIGLOCK(v->domain);
+            break;
+
+        case 4:
+            if ( *reg != (read_cr4() & ~(X86_CR4_PGE|X86_CR4_PSE)) )
+            {
+                DPRINTK("Attempt to change CR4 flags.\n");
+                goto fail;
+            }
             break;
 
         default:

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