Hi Jan,
On 20/10/2020 15:10, Jan Beulich wrote:
There's no need to serialize all sending of vIRQ-s; all that's needed
is serialization against the closing of the respective event channels
(so far by means of a barrier). To facilitate the conversion, switch to
an ordinary write locked region in evtchn_close().
Signed-off-by: Jan Beulich <jbeul...@suse.com>
---
v2: Don't introduce/use rw_barrier() here. Add comment to
evtchn_bind_virq(). Re-base.
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -160,7 +160,7 @@ struct vcpu *vcpu_create(struct domain *
v->vcpu_id = vcpu_id;
v->dirty_cpu = VCPU_CPU_CLEAN;
- spin_lock_init(&v->virq_lock);
+ rwlock_init(&v->virq_lock);
tasklet_init(&v->continue_hypercall_tasklet, NULL, NULL);
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -449,6 +449,13 @@ int evtchn_bind_virq(evtchn_bind_virq_t
spin_unlock_irqrestore(&chn->lock, flags);
+ /*
+ * If by any, the update of virq_to_evtchn[] would need guarding by
+ * virq_lock, but since this is the last action here, there's no strict
+ * need to acquire the lock. Hnece holding event_lock isn't helpful
s/Hnece/Hence/
+ * anymore at this point, but utilize that its unlocking acts as the
+ * otherwise necessary smp_wmb() here.
+ */
v->virq_to_evtchn[virq] = bind->port = port;
I think all access to v->virq_to_evtchn[virq] should use ACCESS_ONCE()
or {read, write}_atomic() to avoid any store/load tearing.
Cheers,
--
Julien Grall
