KVM: nVMX: remove incorrect vpid check in nested invvpid emulation

This patch removes the vpid check when emulating nested invvpid
instruction of type all-contexts invalidation. The existing code is
incorrect because:
 (1) According to Intel SDM Vol 3, Section "INVVPID - Invalidate
     Translations Based on VPID", invvpid instruction does not check
     vpid in the invvpid descriptor when its type is all-contexts
     invalidation.
 (2) According to the same document, invvpid of type all-contexts
     invalidation does not require there is an active VMCS, so/and
     get_vmcs12() in the existing code may result in a NULL-pointer
     dereference. In practice, it can crash both KVM itself and L1
     hypervisors that use invvpid (e.g. Xen).

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx.c

@@ -7394,11 +7394,6 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
 
 	switch (type) {
 	case VMX_VPID_EXTENT_ALL_CONTEXT:
-		if (get_vmcs12(vcpu)->virtual_processor_id == 0) {
-			nested_vmx_failValid(vcpu,
-				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
-			return 1;
-		}
 		__vmx_flush_tlb(vcpu, to_vmx(vcpu)->nested.vpid02);
 		nested_vmx_succeed(vcpu);
 		break;