File 58383d46-x86emul-CMOVcc-always-writes-its-destination.patch of Package xen.6117

# Commit cc53a74291ea5dd5b2c9a327dc386c0e5f859237
# Date 2016-11-25 14:31:50 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86emul: CMOVcc always writes its destination

This would be benign if there wasn't the zero-extending side effect of
32-bit operations in 64-bit mode.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/tools/tests/x86_emulator/test_x86_emulator.c
+++ b/tools/tests/x86_emulator/test_x86_emulator.c
@@ -632,6 +632,21 @@ int main(int argc, char **argv)
     printf("okay\n");
 #else
     printf("skipped\n");
+
+    printf("%-40s", "Testing cmovz %ecx,%eax...");
+    instr[0] = 0x0f; instr[1] = 0x44; instr[2] = 0xc1;
+    regs.eflags = 0x200;
+    regs.eip    = (unsigned long)&instr[0];
+    regs.rax    = 0x1111111122222222;
+    regs.rcx    = 0x3333333344444444;
+    rc = x86_emulate(&ctxt, &emulops);
+    if ( (rc != X86EMUL_OKAY) ||
+         (regs.rax != 0x0000000022222222) ||
+         (regs.rcx != 0x3333333344444444) ||
+         (regs.eflags != 0x200) ||
+         (regs.eip != (unsigned long)&instr[3]) )
+        goto fail;
+    printf("okay\n");
 #endif
 
 #define decl_insn(which) extern const unsigned char which[], which##_len[]
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4242,9 +4242,8 @@ x86_emulate(
     }
 
     case 0x40 ... 0x4f: /* cmovcc */
-        dst.val = src.val;
-        if ( !test_cc(b, _regs.eflags) )
-            dst.type = OP_NONE;
+        if ( test_cc(b, _regs.eflags) )
+            dst.val = src.val;
         break;
 
     case 0x34: /* sysenter */ {