[Xen-devel] [PATCH v4 06/10] xen/common: Restore IRQ affinity when hotplugging a pCPU

[Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>]

Non-boot pCPUs are being hot-unplugged during the system suspend to
RAM and hotplugged during the resume. When non-boot pCPUs are
hot-unplugged the interrupts that were targeted to them are migrated
to the boot pCPU.
On suspend, each guest could have its own wake-up devices/interrupts
(passthrough) that could trigger the system resume. These interrupts
could be targeted to a non-boot pCPU, e.g. if the guest's vCPU is
pinned to a non-boot pCPU. Due to the hot-unplug of non-boot pCPUs
during the suspend such interrupts will be migrated from non-boot pCPUs
to the boot pCPU (this is fine). However, when non-boot pCPUs are
hotplugged on resume, these interrupts are not migrated back to non-boot
pCPUs, i.e. IRQ affinity is not restored on resume (this is wrong).
This patch adds the restoration of IRQ affinity when a pCPU is hotplugged.

Signed-off-by: Mirela Simonovic <mirela.simonovic@xxxxxxxxxx>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>

---
CC: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
CC: Dario Faggioli <dfaggioli@xxxxxxxx>
---
Changes in v2:
-Instead of checking whether the affinity was broken check whether
 vcpu's processor has changed in order to trigger restoring of the
 IRQ affinity
-Fix commit message

Changes in v4:
-Added reviewed by Dario
---
 xen/common/schedule.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index 049f93f7aa..ccf936db83 100644
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -737,6 +737,7 @@ void restore_vcpu_affinity(struct domain *d)
     for_each_vcpu ( d, v )
     {
         spinlock_t *lock;
+        unsigned int old_cpu = v->processor;
 
         ASSERT(!vcpu_runnable(v));
 
@@ -769,6 +770,9 @@ void restore_vcpu_affinity(struct domain *d)
         lock = vcpu_schedule_lock_irq(v);
         v->processor = SCHED_OP(vcpu_scheduler(v), pick_cpu, v);
         spin_unlock_irq(lock);
+
+        if ( old_cpu != v->processor )
+            sched_move_irqs(v);
     }
 
     domain_update_node_affinity(d);
-- 
2.13.0


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