[Xen-changelog] [xen-unstable] x86_emulate: Emulate CLFLUSH instruction

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

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1271353678 -3600
# Node ID d18e6a6c618af4f25a9e1a57c9e3eac55921678c
# Parent  ffffddc4b1e030cce6bd4d12c4409c94599c1abf
x86_emulate: Emulate CLFLUSH instruction

We recently found that FreeBSD 8.0 guest failed to install and boot on
Xen. The reason was that FreeBSD detected clflush feature and invoked
this instruction to flush MMIO space. This caused a page fault; but
x86_emulate.c failed to emulate this instruction (not supported). As a
result, a page fault was detected inside FreeBSD. A similar issue was
reported earlier.

http://lists.xensource.com/archives/html/xen-devel/2010-03/msg00362.html

From: Wei Huang <wei.huang2@xxxxxxx>
Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletion(-)

diff -r ffffddc4b1e0 -r d18e6a6c618a xen/arch/x86/x86_emulate/x86_emulate.c
--- a/xen/arch/x86/x86_emulate/x86_emulate.c    Thu Apr 15 17:36:55 2010 +0100
+++ b/xen/arch/x86/x86_emulate/x86_emulate.c    Thu Apr 15 18:47:58 2010 +0100
@@ -227,7 +227,8 @@ static uint8_t twobyte_table[256] = {
     DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM, 0, 0,
     /* 0xA8 - 0xAF */
     ImplicitOps, ImplicitOps, 0, DstBitBase|SrcReg|ModRM,
-    DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM, 0, DstReg|SrcMem|ModRM,
+    DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM,
+    ImplicitOps|ModRM, DstReg|SrcMem|ModRM,
     /* 0xB0 - 0xB7 */
     ByteOp|DstMem|SrcReg|ModRM, DstMem|SrcReg|ModRM,
     DstReg|SrcMem|ModRM|Mov, DstBitBase|SrcReg|ModRM,
@@ -4008,6 +4009,19 @@ x86_emulate(
         emulate_2op_SrcV_nobyte("bts", src, dst, _regs.eflags);
         break;
 
+    case 0xae: /* Grp15 */
+        switch ( modrm_reg & 7 )
+        {
+        case 7: /* clflush */
+            fail_if(ops->wbinvd == NULL);
+            if ( (rc = ops->wbinvd(ctxt)) != 0 )
+                goto done;
+            break;
+        default:
+            goto cannot_emulate;
+        }
+        break;
+
     case 0xaf: /* imul */
         _regs.eflags &= ~(EFLG_OF|EFLG_CF);
         switch ( dst.bytes )

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