KVM: MMU: Disassociate direct maps from guest levels

Direct maps are linear translations for a section of memory, used for
real mode or with large pages.  As such, they are independent of the guest
levels.

Teach the mmu about this by making page->role.glevels = 0 for direct maps.
This allows direct maps to be shared among real mode and the various paging
modes.
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/mmu.c

@@ -1329,6 +1329,8 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu,
 	role = vcpu->arch.mmu.base_role;
 	role.level = level;
 	role.direct = direct;
+	if (role.direct)
+		role.glevels = 0;
 	role.access = access;
 	if (vcpu->arch.mmu.root_level <= PT32_ROOT_LEVEL) {
 		quadrant = gaddr >> (PAGE_SHIFT + (PT64_PT_BITS * level));