KVM: x86/mmu: Clear 'role.host_mmu_la57_top_p4d' when calculating chi…

…ld SP role

The 'role.host_mmu_la57_top_p4d' bit is only allowed for L4 SP and
should not be inherited when calculating the child SP role. Otherwise,
wrong spte will be set in drop_parent_pte() and it will result in a
broken SPT.

Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: #6

arch/x86/kvm/mmu/mmu.c

@@ -2333,6 +2333,7 @@ static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct,
  role.access = access;
  role.direct = direct;
  role.passthrough = 0;
+ role.host_mmu_la57_top_p4d = 0;
 
  /*
  * If the guest has 4-byte PTEs then that means it's using 32-bit,