[Xen-changelog] [xen staging] x86/IRQ: deal with move cleanup count state in fixup_irqs()

[patchbot@xxxxxxx]

commit 472e0b74c5c4720c5aa70c0ad85c587679bde868
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Jul 22 11:41:55 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jul 22 11:41:55 2019 +0200

    x86/IRQ: deal with move cleanup count state in fixup_irqs()
    
    The cleanup IPI may get sent immediately before a CPU gets removed from
    the online map. In such a case the IPI would get handled on the CPU
    being offlined no earlier than in the interrupts disabled window after
    fixup_irqs()' main loop. This is too late, however, because a possible
    affinity change may incur the need for vector assignment, which will
    fail when the IRQ's move cleanup count is still non-zero.
    
    To fix this
    - record the set of CPUs the cleanup IPIs gets actually sent to alongside
      setting their count,
    - adjust the count in fixup_irqs(), accounting for all CPUs that the
      cleanup IPI was sent to, but that are no longer online,
    - bail early from the cleanup IPI handler when the CPU is no longer
      online, to prevent double accounting.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/irq.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 372d248a60..a55f3d4af8 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -675,6 +675,9 @@ void irq_move_cleanup_interrupt(struct cpu_user_regs *regs)
     ack_APIC_irq();
 
     me = smp_processor_id();
+    if ( !cpu_online(me) )
+        return;
+
     for ( vector = FIRST_DYNAMIC_VECTOR;
           vector <= LAST_HIPRIORITY_VECTOR; vector++)
     {
@@ -735,11 +738,14 @@ unlock:
 
 static void send_cleanup_vector(struct irq_desc *desc)
 {
-    cpumask_t cleanup_mask;
+    cpumask_and(desc->arch.old_cpu_mask, desc->arch.old_cpu_mask,
+                &cpu_online_map);
+    desc->arch.move_cleanup_count = cpumask_weight(desc->arch.old_cpu_mask);
 
-    cpumask_and(&cleanup_mask, desc->arch.old_cpu_mask, &cpu_online_map);
-    desc->arch.move_cleanup_count = cpumask_weight(&cleanup_mask);
-    send_IPI_mask(&cleanup_mask, IRQ_MOVE_CLEANUP_VECTOR);
+    if ( desc->arch.move_cleanup_count )
+        send_IPI_mask(desc->arch.old_cpu_mask, IRQ_MOVE_CLEANUP_VECTOR);
+    else
+        release_old_vec(desc);
 
     desc->arch.move_in_progress = 0;
 }
@@ -2419,6 +2425,16 @@ void fixup_irqs(const cpumask_t *mask, bool verbose)
              vector <= LAST_HIPRIORITY_VECTOR )
             cpumask_and(desc->arch.cpu_mask, desc->arch.cpu_mask, mask);
 
+        if ( desc->arch.move_cleanup_count )
+        {
+            /* The cleanup IPI may have got sent while we were still online. */
+            cpumask_andnot(&affinity, desc->arch.old_cpu_mask,
+                           &cpu_online_map);
+            desc->arch.move_cleanup_count -= cpumask_weight(&affinity);
+            if ( !desc->arch.move_cleanup_count )
+                release_old_vec(desc);
+        }
+
         cpumask_copy(&affinity, desc->affinity);
         if ( !desc->action || cpumask_subset(&affinity, mask) )
         {
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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