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Re: [PATCH] xen/events: fix get_global_virq_handler() usage without hardware domain
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Juergen Gross <jgross@xxxxxxxx>
- Date: Thu, 6 Mar 2025 17:06:27 +0100
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 06 Mar 2025 16:06:37 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 06.03.25 17:00, Jan Beulich wrote:
On 06.03.2025 16:54, Juergen Gross wrote:
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -1036,7 +1036,9 @@ int set_global_virq_handler(struct domain *d, uint32_t
virq)
{
old = global_virq_handlers[virq];
hdl = get_global_virq_handler(virq);
- if ( hdl != d )
+ if ( !hdl )
+ global_virq_handlers[virq] = d;
+ else if ( hdl != d )
{
read_lock(&hdl->event_lock);
@@ -1091,7 +1093,7 @@ struct domain *lock_dom_exc_handler(void)
struct domain *d;
d = get_global_virq_handler(VIRQ_DOM_EXC);
- if ( unlikely(!get_domain(d)) )
+ if ( unlikely(!d || !get_domain(d)) )
According to my understanding of how unlikely() works this wants to be
if ( unlikely(!d) || unlikely(!get_domain(d)) )
Of course I could also live with being given an explanation of why my
understanding is wrong.
I was unsure, so I looked through the code until I found a case where
2 conditions were tested as "unlikely". I might have found a wrong example.
I'll change it as you are suggesting.
return NULL;
read_lock(&d->event_lock);
There's one more change needed: get_domain_state() needs to avoid calling
unlock_dom_exc_handler() when "hdl" is NULL.
Oh, right. Will add.
Juergen
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