KVM: MMU: fix conflict access permissions in direct sp

In no-direct mapping, we mark sp is 'direct' when we mapping the
guest's larger page, but its access is encoded form upper page-struct
entire not include the last mapping, it will cause access conflict.

For example, have this mapping:
        [W]
      / PDE1 -> |---|
  P[W]          |   | LPA
      \ PDE2 -> |---|
        [R]

P have two children, PDE1 and PDE2, both PDE1 and PDE2 mapping the
same lage page(LPA). The P's access is WR, PDE1's access is WR,
PDE2's access is RO(just consider read-write permissions here)

When guest access PDE1, we will create a direct sp for LPA, the sp's
access is from P, is W, then we will mark the ptes is W in this sp.

Then, guest access PDE2, we will find LPA's shadow page, is the same as
PDE's, and mark the ptes is RO.

So, if guest access PDE1, the incorrect #PF is occured.

Fixed by encode the last mapping access into direct shadow page

Signed-off-by: Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 89d66ca..2331bdc 100644 (file)
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -342,6 +342,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                        /* advance table_gfn when emulating 1gb pages with 4k */
                        if (delta == 0)
                                table_gfn += PT_INDEX(addr, level);
+                       access &= gw->pte_access;
                } else {
                        direct = 0;
                        table_gfn = gw->table_gfn[level - 2];