KVM: nVMX: Drop obsolete (and pointless) pdptrs_changed() check

Remove the pdptrs_changed() check when loading L2's CR3.  The set of
available registers is always reset when switching VMCSes (see commit
e5d03de5, "KVM: nVMX: Reset register cache (available and dirty
masks) on VMCS switch"), thus the "are PDPTRs available" check will
always fail.  And even if it didn't fail, reading guest memory to check
the PDPTRs is just as expensive as reading guest memory to load 'em.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210607090203.133058-2-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -1118,12 +1118,10 @@ static int nested_vmx_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3, bool ne
 	 * must not be dereferenced.
 	 */
 	if (!nested_ept && is_pae_paging(vcpu) &&
-	    (cr3 != kvm_read_cr3(vcpu) || pdptrs_changed(vcpu))) {
-		if (CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) {
+	    CC(!load_pdptrs(vcpu, vcpu->arch.walk_mmu, cr3))) {
 		*entry_failure_code = ENTRY_FAIL_PDPTE;
 		return -EINVAL;
 	}
-	}
 
 	/*
 	 * Unconditionally skip the TLB flush on fast CR3 switch, all TLB