KVM: VMX: vmx_set_cr0 expects kvm->srcu locked

(cherry picked from commit 7a4f5ad0)

vmx_set_cr0 is called from vcpu run context, therefore it expects
kvm->srcu to be held (for setting up the real-mode TSS).
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

arch/x86/kvm/vmx.c

@@ -3915,7 +3915,9 @@ static int vmx_vcpu_reset(struct kvm_vcpu *vcpu)
 		vmcs_write16(VIRTUAL_PROCESSOR_ID, vmx->vpid);
 
 	vmx->vcpu.arch.cr0 = X86_CR0_NW | X86_CR0_CD | X86_CR0_ET;
+	vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu);
 	vmx_set_cr0(&vmx->vcpu, kvm_read_cr0(vcpu)); /* enter rmode */
+	srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);
 	vmx_set_cr4(&vmx->vcpu, 0);
 	vmx_set_efer(&vmx->vcpu, 0);
 	vmx_fpu_activate(&vmx->vcpu);