KVM: VMX: Refresh list of user return MSRs after setting guest CPUID

After a CPUID update, refresh the list of user return MSRs that are
loaded into hardware when running the vCPU.  This is necessary to handle
the oddball case where userspace exposes X86_FEATURE_RDTSCP to the guest
after the vCPU is running.

Fixes: 0023ef39 ("kvm: vmx: Set IA32_TSC_AUX for legacy mode guests")
Fixes: 4e47c7a6 ("KVM: VMX: Add instruction rdtscp support for guest")
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-35-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -7170,6 +7170,8 @@ static void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
 	/* xsaves_enabled is recomputed in vmx_compute_secondary_exec_control(). */
 	vcpu->arch.xsaves_enabled = false;
 
+	vmx_setup_uret_msrs(vmx);
+
 	if (cpu_has_secondary_exec_ctrls()) {
 		vmx_compute_secondary_exec_control(vmx);
 		vmcs_set_secondary_exec_control(vmx);