x86/apic: Get rid of apic->target_cpus

The target_cpus() callback of the apic struct is not really useful. Some
APICs return cpu_online_mask and others cpus_all_mask. The latter is bogus
as it does not take holes in the cpus_possible_mask into account.

Replace it with cpus_online_mask which makes the most sense and remove the
callback.

The usage sites will be removed in a later step anyway, so get rid of it
now to have incremental changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Juergen Gross <jgross@suse.com>
Tested-by: Yu Chen <yu.c.chen@intel.com>
Acked-by: Juergen Gross <jgross@suse.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Alok Kataria <akataria@vmware.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rui Zhang <rui.zhang@intel.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Len Brown <lenb@kernel.org>
Link: https://lkml.kernel.org/r/20170913213154.070850916@linutronix.de

arch/x86/kernel/apic/apic_noop.c

@@ -83,12 +83,6 @@ static int noop_apic_id_registered(void)
 	return physid_isset(0, phys_cpu_present_map);
 }
 
-static const struct cpumask *noop_target_cpus(void)
-{
-	/* only BSP here */
-	return cpumask_of(0);
-}
-
 static void noop_vector_allocation_domain(int cpu, struct cpumask *retmask,
 					  const struct cpumask *mask)
 {
@@ -127,7 +121,6 @@ struct apic apic_noop __ro_after_init = {
 	/* logical delivery broadcast to all CPUs: */
 	.irq_dest_mode			= 1,
 
-	.target_cpus			= noop_target_cpus,
 	.disable_esr			= 0,
 	.dest_logical			= APIC_DEST_LOGICAL,
 	.check_apicid_used		= default_check_apicid_used,