[Xen-changelog] [xen staging] x86/IRQ: target online CPUs when binding guest IRQ

[patchbot@xxxxxxx]

commit 0d7fd5f2b8ede776a8a395c1fd0427139ffa3219
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Jul 22 11:44:50 2019 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Jul 22 11:44:50 2019 +0200

    x86/IRQ: target online CPUs when binding guest IRQ
    
    fixup_irqs() skips interrupts without action. Hence such interrupts can
    retain affinity to just offline CPUs. With "noirqbalance" in effect,
    pirq_guest_bind() so far would have left them alone, resulting in a non-
    working interrupt.
    
    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, 21 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/irq.c b/xen/arch/x86/irq.c
index 10a83efc8e..732ddd4efd 100644
--- a/xen/arch/x86/irq.c
+++ b/xen/arch/x86/irq.c
@@ -1695,9 +1695,27 @@ int pirq_guest_bind(struct vcpu *v, struct pirq *pirq, 
int will_share)
 
         desc->status |= IRQ_GUEST;
 
-        /* Attempt to bind the interrupt target to the correct CPU. */
-        if ( !opt_noirqbalance && (desc->handler->set_affinity != NULL) )
-            desc->handler->set_affinity(desc, cpumask_of(v->processor));
+        /*
+         * Attempt to bind the interrupt target to the correct (or at least
+         * some online) CPU.
+         */
+        if ( desc->handler->set_affinity )
+        {
+            const cpumask_t *affinity = NULL;
+
+            if ( !opt_noirqbalance )
+                affinity = cpumask_of(v->processor);
+            else if ( !cpumask_intersects(desc->affinity, &cpu_online_map) )
+            {
+                cpumask_setall(desc->affinity);
+                affinity = &cpumask_all;
+            }
+            else if ( !cpumask_intersects(desc->arch.cpu_mask,
+                                          &cpu_online_map) )
+                affinity = desc->affinity;
+            if ( affinity )
+                desc->handler->set_affinity(desc, affinity);
+        }
 
         desc->status &= ~IRQ_DISABLED;
         desc->handler->startup(desc);
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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