[PATCH for-4.19 1/9] x86/irq: remove offline CPUs from old CPU mask when adjusting move_cleanup_count

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

When adjusting move_cleanup_count to account for CPUs that are offline also
adjust old_cpu_mask, otherwise further calls to fixup_irqs() could subtract
those again creating and create an imbalance in move_cleanup_count.

Fixes: 472e0b74c5c4 ('x86/IRQ: deal with move cleanup count state in 
fixup_irqs()')
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/irq.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index c16205a9beb6..9716e00e873b 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -2572,6 +2572,14 @@ void fixup_irqs(const cpumask_t *mask, bool verbose)
             desc->arch.move_cleanup_count -= cpumask_weight(affinity);
             if ( !desc->arch.move_cleanup_count )
                 release_old_vec(desc);
+            else
+                /*
+                 * Adjust old_cpu_mask to account for the offline CPUs,
+                 * otherwise further calls to fixup_irqs() could subtract those
+                 * again and possibly underflow the counter.
+                 */
+                cpumask_and(desc->arch.old_cpu_mask, desc->arch.old_cpu_mask,
+                            &cpu_online_map);
         }
 
         if ( !desc->action || cpumask_subset(desc->affinity, mask) )
-- 
2.44.0