KVM: VMX: when entering real mode align segment base to 16 bytes

VMX checks that base is equal segment shifted 4 bits left. Otherwise
guest entry fails.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1896cada805f..bf89ec2cfb82 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1736,9 +1736,13 @@ static void fix_rmode_seg(int seg, struct kvm_save_segment *save)
         save->limit = vmcs_read32(sf->limit);
         save->ar = vmcs_read32(sf->ar_bytes);
         vmcs_write16(sf->selector, save->base >> 4);
-        vmcs_write32(sf->base, save->base & 0xfffff);
+        vmcs_write32(sf->base, save->base & 0xffff0);
         vmcs_write32(sf->limit, 0xffff);
         vmcs_write32(sf->ar_bytes, 0xf3);
+        if (save->base & 0xf)
+                printk_once(KERN_WARNING "kvm: segment base is not paragraph"
+                            " aligned when entering protected mode (seg=%d)",
+                            seg);
 }
 
 static void enter_rmode(struct kvm_vcpu *vcpu)