The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 07ce121d93a5e5fb2440a24da3dbf408fcee978e # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025101625-rebalance-humbling-87a2@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 07ce121d93a5e5fb2440a24da3dbf408fcee978e Mon Sep 17 00:00:00 2001 From: Jason Andryuk jason.andryuk@amd.com Date: Wed, 27 Aug 2025 20:36:02 -0400 Subject: [PATCH] xen/events: Return -EEXIST for bound VIRQs

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.

Cc: stable@vger.kernel.org Signed-off-by: Jason Andryuk jason.andryuk@amd.com Reviewed-by: Juergen Gross jgross@suse.com Signed-off-by: Juergen Gross jgross@suse.com Message-ID: 20250828003604.8949-3-jason.andryuk@amd.com

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c index 374231d84e4f..b060b5a95f45 100644 --- a/drivers/xen/events/events_base.c +++ b/drivers/xen/events/events_base.c @@ -1314,10 +1314,12 @@ int bind_interdomain_evtchn_to_irq_lateeoi(struct xenbus_device *dev, } EXPORT_SYMBOL_GPL(bind_interdomain_evtchn_to_irq_lateeoi);

-static int find_virq(unsigned int virq, unsigned int cpu, evtchn_port_t *evtchn) +static int find_virq(unsigned int virq, unsigned int cpu, evtchn_port_t *evtchn, + bool percpu) { struct evtchn_status status; evtchn_port_t port; + bool exists = false;

memset(&status, 0, sizeof(status)); for (port = 0; port < xen_evtchn_max_channels(); port++) { @@ -1330,12 +1332,16 @@ static int find_virq(unsigned int virq, unsigned int cpu, evtchn_port_t *evtchn) continue; if (status.status != EVTCHNSTAT_virq) continue; - if (status.u.virq == virq && status.vcpu == xen_vcpu_nr(cpu)) { + if (status.u.virq != virq) + continue; + if (status.vcpu == xen_vcpu_nr(cpu)) { *evtchn = port; return 0; + } else if (!percpu) { + exists = true; } } - return -ENOENT; + return exists ? -EEXIST : -ENOENT; }

/** @@ -1382,8 +1388,11 @@ 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) { + __unbind_from_irq(info, info->irq); + goto out; + } }

ret = xen_irq_info_virq_setup(info, cpu, evtchn, virq);