From: Jan Beulich <jbeulich@suse.com>
Date: Thu, 9 Jun 2016 13:45:23 +0000 (+0200)
Subject: x86/XSTATE: clarify XRSTOR() macro
X-Git-Tag: archive/raspbian/4.8.0-1+rpi1~1^2~999
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=baabb747749e408030613bdc42ae9f0cbe489ba8;p=xen.git

x86/XSTATE: clarify XRSTOR() macro

Make obvious that xcomp_bv is expected to be clear when we get here
with XSTATE_COMPACTION_ENABLED not set.

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

diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index 1fd1ce8c24..d90e89ed0a 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -387,8 +387,11 @@ void xrstor(struct vcpu *v, uint64_t mask)
         { \
             if ( unlikely(!(ptr->xsave_hdr.xcomp_bv & \
                             XSTATE_COMPACTION_ENABLED)) ) \
-                ptr->xsave_hdr.xcomp_bv |= ptr->xsave_hdr.xstate_bv | \
-                                           XSTATE_COMPACTION_ENABLED; \
+            { \
+                ASSERT(!ptr->xsave_hdr.xcomp_bv); \
+                ptr->xsave_hdr.xcomp_bv = ptr->xsave_hdr.xstate_bv | \
+                                          XSTATE_COMPACTION_ENABLED; \
+            } \
             _xrstor(pfx "0x0f,0xc7,0x1f"); /* xrstors */ \
         } \
         else \