x86/irq: Reorganize the search in assign_irq_vector

Split out the code which advances the target cpu for the search so we can
reuse it for the next patch which adds an early validation check for the
vectormask which we get from the apic.

Add comments while at it.

Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Borislav Petkov <[email protected]>
Tested-by: Joe Lawrence <[email protected]>
Cc: Jiang Liu <[email protected]>
Cc: Jeremiah Mahler <[email protected]>
Cc: [email protected]
Cc: Guenter Roeck <[email protected]>
Cc: [email protected] #4.3+
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>

1 files changed, 16 insertions, 8 deletions

diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
index 613b1cd8eecb..cef31955ab18 100644
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -157,14 +157,9 @@ next:
 			vector = FIRST_EXTERNAL_VECTOR + offset;
 		}
 
-		if (unlikely(current_vector == vector)) {
-			cpumask_or(searched_cpumask, searched_cpumask,
-				   vector_cpumask);
-			cpumask_andnot(vector_cpumask, mask, searched_cpumask);
-			cpu = cpumask_first_and(vector_cpumask,
-						cpu_online_mask);
-			continue;
-		}
+		/* If the search wrapped around, try the next cpu */
+		if (unlikely(current_vector == vector))
+			goto next_cpu;
 
 		if (test_bit(vector, used_vectors))
 			goto next;
@@ -186,6 +181,19 @@ next:
 		d->cfg.vector = vector;
 		cpumask_copy(d->domain, vector_cpumask);
 		goto success;
+
+next_cpu:
+		/*
+		 * We exclude the current @vector_cpumask from the requested
+		 * @mask and try again with the next online cpu in the
+		 * result. We cannot modify @mask, so we use @vector_cpumask
+		 * as a temporary buffer here as it will be reassigned when
+		 * calling apic->vector_allocation_domain() above.
+		 */
+		cpumask_or(searched_cpumask, searched_cpumask, vector_cpumask);
+		cpumask_andnot(vector_cpumask, mask, searched_cpumask);
+		cpu = cpumask_first_and(vector_cpumask, cpu_online_mask);
+		continue;
 	}
 	return -ENOSPC;