[Lucid][SRU][PATCH] UBUNTU: SAUCE: (no-up) Fix up KVM: VMX: Fix host userspace gsbase corruption

[Leann Ogasawara]

SRU Justification:

http://bugs.launchpad.net/bugs/787675

I've clearly buggered up a backported patch on Lucid that came in as an
aside for the 2.6.32.26+drm33.11 stable patch set (See bug 681132). The
patch in question is:

    KVM: VMX: Fix host userspace gsbase corruption

    We now use load_gs_index() to load gs safely; unfortunately this also
    changes MSR_KERNEL_GS_BASE, which we managed separately. This resulted
    in confusion and breakage running 32-bit host userspace on a 64-bit kernel.

The original thread regarding this patch can be read at:

https://lists.ubuntu.com/archives/kernel-team/2010-November/013655.html

The attached patch correctly fixes up the accidental deletion of a line
of code, and correctly removes the intended line. Please apply to Lucid.
I've also built a test kernel and referenced it in the bug.  I'm hoping
for testing feedback from Jiang who originally brought the mistake to my
attention.

Thanks,
Leann

The following changes since commit 800e98aaa03cf2134fb3b1a7c11f59e93fa97c23:
  Thomas Schlichter (1):
        UBUNTU: SAUCE: vesafb: enable mtrr WC by default

are available in the git repository at:

  git://kernel.ubuntu.com/ogasawara/ubuntu-lucid.git lp787675

Leann Ogasawara (1):
      UBUNTU: SAUCE: (no-up) Fix up KVM: VMX: Fix host userspace gsbase corruption

 arch/x86/kvm/vmx.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

>From 7766255c19171ecd6961ea9b6455d0de11245d19 Mon Sep 17 00:00:00 2001
From: Leann Ogasawara <leann.ogasawara at canonical.com>
Date: Tue, 24 May 2011 09:40:12 -0700
Subject: [PATCH] UBUNTU: SAUCE: (no-up) Fix up KVM: VMX: Fix host userspace gsbase corruption

BugLink: http://bugs.launchpad.net/bugs/787675

The backport for the following commit was incorrect, eg. it removed a
line which it shouldn't have.

  commit 6cbdc7ba48dff850c233a1ea1abe87a6d0cde2dd
  Author: Avi Kivity <avi at redhat.com>
  Date:   Thu Nov 11 12:37:26 2010 +0200

    KVM: VMX: Fix host userspace gsbase corruption

Fix up the backport to be correct.

Signed-off-by: Leann Ogasawara <leann.ogasawara at canonical.com>
---
 arch/x86/kvm/vmx.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 77c3287..e3222ab 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -699,7 +699,7 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
 	if (vmx->host_state.gs_ldt_reload_needed) {
 		kvm_load_ldt(vmx->host_state.ldt_sel);
 #ifdef CONFIG_X86_64
-		wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
+		load_gs_index(vmx->host_state.gs_sel);
 #else
 		loadsegment(gs, vmx->host_state.gs_sel);
 #endif
-- 
1.7.0.4