File 58821300-x86-segment-attribute-handling.patch of Package xen.11298

# Commit 366ff5f1b3252f9069d5aedb2ffc2567bb0a37c9
# Date 2017-01-20 14:39:12 +0100
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86: segment attribute handling adjustments

Null selector loads into SS (possible in 64-bit mode only, and only in
rings other than ring 3) must not alter SS.DPL. (This was found to be
an issue on KVM, and fixed in Linux commit 33ab91103b.)

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

--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -1208,6 +1208,11 @@ protmode_load_seg(
         }
         memset(sreg, 0, sizeof(*sreg));
         sreg->sel = sel;
+
+        /* Since CPL == SS.DPL, we need to put back DPL. */
+        if ( seg == x86_seg_ss )
+            sreg->attr.fields.dpl = sel;
+
         return X86EMUL_OKAY;
     }