KVM: Hack real-mode segments on vmx from KVM_SET_SREGS

As usual, we need to mangle segment registers when emulating real mode
as vm86 has specific constraints.  We special case the reset segment base,
and set the "access rights" (or descriptor flags) to vm86 comaptible values.

This fixes reboot on vmx.

Signed-off-by: Avi Kivity <avi@qumranet.com>

diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
index 027a9625ef90160551b0eaf7b70b2adec2ca3ef6..578dff5424e3f5c4eaa9faab1c8adf12d2ee67ee 100644 (file)
--- a/drivers/kvm/vmx.c
+++ b/drivers/kvm/vmx.c
@@ -864,7 +864,14 @@ static void vmx_set_segment(struct kvm_vcpu *vcpu,
        vmcs_writel(sf->base, var->base);
        vmcs_write32(sf->limit, var->limit);
        vmcs_write16(sf->selector, var->selector);
-       if (var->unusable)
+       if (vcpu->rmode.active && var->s) {
+               /*
+                * Hack real-mode segments into vm86 compatibility.
+                */
+               if (var->base == 0xffff0000 && var->selector == 0xf000)
+                       vmcs_writel(sf->base, 0xf0000);
+               ar = 0xf3;
+       } else if (var->unusable)
                ar = 1 << 16;
        else {
                ar = var->type & 15;