[PATCH] KVM/VMX: Check ept_pointer before flushing ept tlb

[ltykernel]

From: Lan Tianyu <tianyu....@microsoft.com>

This patch is to initialize ept_pointer to INVALID_PAGE and check it
before flushing ept tlb. If ept_pointer is invalidated, bypass the flush
request.

Signed-off-by: Lan Tianyu <tianyu....@microsoft.com>
---
 arch/x86/kvm/vmx.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4555077d69ce..edbc96cb990a 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1580,14 +1580,22 @@ static int vmx_hv_remote_flush_tlb(struct kvm *kvm)
        /*
         * FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE hypercall needs the address of the
         * base of EPT PML4 table, strip off EPT configuration information.
+        * If ept_pointer is invalid pointer, bypass the flush request.
         */
        if (to_kvm_vmx(kvm)->ept_pointers_match != EPT_POINTERS_MATCH) {
-               kvm_for_each_vcpu(i, vcpu, kvm)
+               kvm_for_each_vcpu(i, vcpu, kvm) {
+                       if (!VALID_PAGE(to_vmx(vcpu)->ept_pointer))
+                               return 0;
+
                        ret |= hyperv_flush_guest_mapping(
-                               to_vmx(kvm_get_vcpu(kvm, i))->ept_pointer & 
PAGE_MASK);
+                               to_vmx(vcpu)->ept_pointer & PAGE_MASK);
+               }
        } else {
+               if (!VALID_PAGE(to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer))
+                       return 0;
+
                ret = hyperv_flush_guest_mapping(
-                               to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & 
PAGE_MASK);
+                       to_vmx(kvm_get_vcpu(kvm, 0))->ept_pointer & PAGE_MASK);
        }
 
        spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
@@ -11568,6 +11576,8 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm 
*kvm, unsigned int id)
        vmx->pi_desc.nv = POSTED_INTR_VECTOR;
        vmx->pi_desc.sn = 1;
 
+       vmx->ept_pointer = INVALID_PAGE;
+
        return &vmx->vcpu;
 
 free_vmcs:
-- 
2.14.4