From 43101a862366393aa310c0892388c5d68b6bd3d9 Mon Sep 17 00:00:00 2001
From: CleverMouse <theclevermouse@yandex.ru>
Date: Fri, 7 Mar 2014 10:57:58 +0000
Subject: [PATCH] r4619

git-svn-id: svn://kolibrios.org@4619 a494cfbc-eb01-0410-851d-a64ba20cac60
---
 kernel/trunk/core/mtrr.inc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/trunk/core/mtrr.inc b/kernel/trunk/core/mtrr.inc
index a7aa8b1bde..fcca6e68f8 100644
--- a/kernel/trunk/core/mtrr.inc
+++ b/kernel/trunk/core/mtrr.inc
@@ -821,8 +821,11 @@ endp
 ; Let's hope he would report it to developers...
 proc mtrr_validate
 ; 1. If MTRRs are not supported, they cannot be configured improperly.
-        bt      [cpu_caps], CAPS_MTRR
-        jnc     .exit
+; Note: VirtualBox claims MTRR support in cpuid, but emulates MTRRCAP=0,
+; which is efficiently equivalent to absent MTRRs.
+; So check [num_variable_mtrrs] instead of CAPS_MTRR in [cpu_caps].
+        cmp     [num_variable_mtrrs], 0
+        jz      .exit
 ; 2. If variable-range MTRRs are not configured, this is a problem.
         mov     ecx, 0x2FF
         rdmsr