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Re: [PATCH v2 2/3] xen/events: Return -EEXIST for bound VIRQs
- To: Jürgen Groß <jgross@xxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Wed, 27 Aug 2025 18:11:23 -0400
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- Cc: <xen-devel@xxxxxxxxxxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx>
- Delivery-date: Thu, 28 Aug 2025 00:32:06 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2025-08-27 11:21, Jürgen Groß wrote:
On 26.08.25 02:55, Jason Andryuk wrote:
Change find_virq() to return -EEXIST when a VIRQ is bound to a
different CPU than the one passed in. With that, remove the BUG_ON()
from bind_virq_to_irq() to propogate the error upwards.
Some VIRQs are per-cpu, but others are per-domain or global. Those must
be bound to CPU0 and can then migrate elsewhere. The lookup for
per-domain and global will probably fail when migrated off CPU 0,
especially when the current CPU is tracked. This now returns -EEXIST
instead of BUG_ON().
A second call to bind a per-domain or global VIRQ is not expected, but
make it non-fatal to avoid trying to look up the irq, since we don't
know which per_cpu(virq_to_irq) it will be in.
Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
@@ -1381,8 +1387,9 @@ int bind_virq_to_irq(unsigned int virq, unsigned
int cpu, bool percpu)
evtchn = bind_virq.port;
else {
if (ret == -EEXIST)
- ret = find_virq(virq, cpu, &evtchn);
- BUG_ON(ret < 0);
+ ret = find_virq(virq, cpu, &evtchn, percpu);
+ if (ret)
+ goto out;
I think you are leaking info here. I guess a call of __unbind_from_irq() is
wanted like in the error case below (note that the case of no valid
evtchn is
handled there just fine).
Ok, thanks for catching that.
I'm going to add Cc: stable to the next version of this. While it
doesn't have a Fixes associated, we want this as a prerequisite for patch 3.
Regards,
Jason
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