x86/vector: Store the single CPU targets in apic data

Now that the interrupt affinities are targeted at single CPUs storing them
in a cpumask is overkill. Store them in a dedicated variable.

This does not yet remove the domain cpumasks because the current allocator
relies on them. Preparatory change for the allocator rework.

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/20170913213154.544867277@linutronix.de

arch/x86/kernel/apic/vector.c

@@ -23,6 +23,8 @@
 
 struct apic_chip_data {
 	struct irq_cfg		cfg;
+	unsigned int		cpu;
+	unsigned int		prev_cpu;
 	cpumask_var_t		domain;
 	cpumask_var_t		old_domain;
 	u8			move_in_progress : 1;
@@ -214,6 +216,7 @@ update:
 	cpumask_and(d->old_domain, d->old_domain, cpu_online_mask);
 	d->move_in_progress = !cpumask_empty(d->old_domain);
 	d->cfg.old_vector = d->move_in_progress ? d->cfg.vector : 0;
+	d->prev_cpu = d->cpu;
 	d->cfg.vector = vector;
 	cpumask_copy(d->domain, vector_cpumask);
 success:
@@ -228,6 +231,7 @@ success:
 	cpumask_and(vector_searchmask, vector_searchmask, mask);
 	BUG_ON(apic->cpu_mask_to_apicid(vector_searchmask, irqd,
 					&d->cfg.dest_apicid));
+	d->cpu = cpumask_first(vector_searchmask);
 	return 0;
 }
 
@@ -428,6 +432,7 @@ static void __init init_legacy_irqs(void)
 
 		apicd->cfg.vector = ISA_IRQ_VECTOR(i);
 		cpumask_copy(apicd->domain, cpumask_of(0));
+		apicd->cpu = 0;
 		irq_set_chip_data(i, apicd);
 	}
 }