From: Jan Beulich <jbeulich@suse.com>
Date: Thu, 8 Dec 2016 11:22:33 +0000 (+0100)
Subject: x86emul: simplify {,i}{mul,div} fix
X-Git-Tag: archive/raspbian/4.11.1-1+rpi1~1^2~66^2~3223
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=f5b9217531dac37451845cd83dfd30e4cc1053b4;p=xen.git

x86emul: simplify {,i}{mul,div} fix

Commit 75066cd4ea ("x86emul: fix {,i}mul and {,i}div") can be had with
less code: Simply do the destination register override depending on
DstEax being in effect (the four other ModRM.reg encoded operations of
these two opcodes all use DstMem).

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

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.c b/xen/arch/x86/x86_emulate/x86_emulate.c
index 22b8dc8900..d66ce7ac1c 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.c
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c
@@ -4104,6 +4104,8 @@ x86_emulate(
         break;
 
     case 0xf6 ... 0xf7: /* Grp3 */
+        if ( (d & DstMask) == DstEax )
+            dst.reg = (unsigned long *)&_regs.eax;
         switch ( modrm_reg & 7 )
         {
             unsigned long u[2], v;
@@ -4118,7 +4120,6 @@ x86_emulate(
             emulate_1op("neg", dst, _regs.eflags);
             break;
         case 4: /* mul */
-            dst.reg = (unsigned long *)&_regs.eax;
             _regs.eflags &= ~(EFLG_OF|EFLG_CF);
             switch ( dst.bytes )
             {
@@ -4156,7 +4157,6 @@ x86_emulate(
             }
             break;
         case 5: /* imul */
-            dst.reg = (unsigned long *)&_regs.eax;
         imul:
             _regs.eflags &= ~(EFLG_OF|EFLG_CF);
             switch ( dst.bytes )
@@ -4198,7 +4198,6 @@ x86_emulate(
             }
             break;
         case 6: /* div */
-            dst.reg = (unsigned long *)&_regs.eax;
             switch ( src.bytes )
             {
             case 1:
@@ -4244,7 +4243,6 @@ x86_emulate(
             }
             break;
         case 7: /* idiv */
-            dst.reg = (unsigned long *)&_regs.eax;
             switch ( src.bytes )
             {
             case 1: