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From 38c385caa32752ef176ffd1448e45e0dc94d5043 Mon Sep 17 00:00:00 2001
From: Orit Wasserman <owasserm@redhat.com>
Date: Wed, 9 Oct 2013 10:09:11 +0200
Subject: [PATCH 16/25] Fix real mode guest segments dpl value in savevm

RH-Author: Orit Wasserman <owasserm@redhat.com>
Message-id: <1381313355-15641-7-git-send-email-owasserm@redhat.com>
Patchwork-id: 54802
O-Subject: [RHEL7.0 qemu-kvm v2 06/10] Fix real mode guest segments dpl value in savevm
Bugzilla: 921465
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Juan Quintela <quintela@redhat.com>

Older KVM version put invalid value in the segments registers dpl field for
real mode guests (0x3).
This breaks migration from those hosts to hosts with unrestricted guest support.
We detect it by checking CS dpl value for real mode guest and fix the dpl values
of all the segment registers.

Signed-off-by: Orit Wasserman <owasserm@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
(cherry picked from commit 3e47c249b93d5cc1e0f9404dbe243682598ba8fb)
---
 target-i386/machine.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 target-i386/machine.c |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/target-i386/machine.c b/target-i386/machine.c
index 079a132..8faea62 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -252,6 +252,24 @@ static void cpu_pre_save(void *opaque)
     }
 
     env->fpregs_format_vmstate = 0;
+
+    /*
+     * Real mode guest segments register DPL should be zero.
+     * Older KVM version were setting it wrongly.
+     * Fixing it will allow live migration to host with unrestricted guest
+     * support (otherwise the migration will fail with invalid guest state
+     * error).
+     */
+    if (!(env->cr[0] & CR0_PE_MASK) &&
+        (env->segs[R_CS].flags >> DESC_DPL_SHIFT & 3) != 0) {
+        env->segs[R_CS].flags &= ~(env->segs[R_CS].flags & DESC_DPL_MASK);
+        env->segs[R_DS].flags &= ~(env->segs[R_DS].flags & DESC_DPL_MASK);
+        env->segs[R_ES].flags &= ~(env->segs[R_ES].flags & DESC_DPL_MASK);
+        env->segs[R_FS].flags &= ~(env->segs[R_FS].flags & DESC_DPL_MASK);
+        env->segs[R_GS].flags &= ~(env->segs[R_GS].flags & DESC_DPL_MASK);
+        env->segs[R_SS].flags &= ~(env->segs[R_SS].flags & DESC_DPL_MASK);
+    }
+
 }
 
 static int cpu_post_load(void *opaque, int version_id)
-- 
1.7.1