KVM: x86/PVM: Check the validity of the root page for direct switchin…

…g when PCID is not supported

Similar to the check performed in
pvm_set_host_cr3_for_guest_with_host_pcid(), the HPA of the SPT page
table for direct switching should also be verified in
pvm_set_host_cr3_for_guest_without_host_pcid().

Signed-off-by: Yong He <alexyonghe@tencent.com>
Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Link: #4

arch/x86/kvm/pvm/pvm.c

@@ -774,9 +774,11 @@ static void pvm_set_host_cr3_for_guest_without_host_pcid(struct vcpu_pvm *pvm)
 {
  u64 root_hpa = pvm->vcpu.arch.mmu->root.hpa;
  u64 switch_root = 0;
+ u64 prev_root_hpa = pvm->vcpu.arch.mmu->prev_roots[0].hpa;
 
- if (pvm->vcpu.arch.mmu->prev_roots[0].pgd == pvm->msr_switch_cr3) {
- switch_root = pvm->vcpu.arch.mmu->prev_roots[0].hpa;
+ if (VALID_PAGE(prev_root_hpa) &&
+ pvm->vcpu.arch.mmu->prev_roots[0].pgd == pvm->msr_switch_cr3) {
+ switch_root = prev_root_hpa;
  pvm->switch_flags &= ~SWITCH_FLAGS_NO_DS_CR3;
  } else {
  pvm->switch_flags |= SWITCH_FLAGS_NO_DS_CR3;