FAILED: patch "[PATCH] xen/events: Update virq_to_irq on migration" failed to apply to 5.15-stable tree

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 <[email protected]>.

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 3fcc8e146935415d69ffabb5df40ecf50e106131
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025101617-sullen-exploit-1442@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 3fcc8e146935415d69ffabb5df40ecf50e106131 Mon Sep 17 00:00:00 2001
From: Jason Andryuk <[email protected]>
Date: Wed, 27 Aug 2025 20:36:03 -0400
Subject: [PATCH] xen/events: Update virq_to_irq on migration

VIRQs come in 3 flavors, per-VPU, per-domain, and global, and the VIRQs are tracked in per-cpu virq_to_irq arrays.

Per-domain and global VIRQs must be bound on CPU 0, and bind_virq_to_irq() sets the per_cpu virq_to_irq at registration time Later, the interrupt can migrate, and info->cpu is updated. When calling __unbind_from_irq(), the per-cpu virq_to_irq is cleared for a different cpu. If bind_virq_to_irq() is called again with CPU 0, the stale irq is returned. There won't be any irq_info for the irq, so things break.

Make xen_rebind_evtchn_to_cpu() update the per_cpu virq_to_irq mappings to keep them update to date with the current cpu. This ensures the correct virq_to_irq is cleared in __unbind_from_irq().

Message-ID: <[email protected]>

index b060b5a95f45..9478fae014e5 100644
@@ -1797,9 +1797,20 @@ static int xen_rebind_evtchn_to_cpu(struct irq_info *info, unsigned int tcpu)
 	 * virq or IPI channel, which don't actually need to be rebound. Ignore
 	 * it, but don't do the xenlinux-level rebind in that case.
 	 */
-	if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
+	if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0) {
+		int old_cpu = info->cpu;
+
 		bind_evtchn_to_cpu(info, tcpu, false);
 
+		if (info->type == IRQT_VIRQ) {
+			int virq = info->u.virq;
+			int irq = per_cpu(virq_to_irq, old_cpu)[virq];
+
+			per_cpu(virq_to_irq, old_cpu)[virq] = -1;
+			per_cpu(virq_to_irq, tcpu)[virq] = irq;
+		}
+	}
+
 	do_unmask(info, EVT_MASK_REASON_TEMPORARY);
 
 	return 0;

From: Jason Andryuk <[email protected]>

[ Upstream commit 3fcc8e146935415d69ffabb5df40ecf50e106131 ]

VIRQs come in 3 flavors, per-VPU, per-domain, and global, and the VIRQs are tracked in per-cpu virq_to_irq arrays.

Per-domain and global VIRQs must be bound on CPU 0, and bind_virq_to_irq() sets the per_cpu virq_to_irq at registration time Later, the interrupt can migrate, and info->cpu is updated. When calling __unbind_from_irq(), the per-cpu virq_to_irq is cleared for a different cpu. If bind_virq_to_irq() is called again with CPU 0, the stale irq is returned. There won't be any irq_info for the irq, so things break.

Make xen_rebind_evtchn_to_cpu() update the per_cpu virq_to_irq mappings to keep them update to date with the current cpu. This ensures the correct virq_to_irq is cleared in __unbind_from_irq().

Message-ID: <[email protected]>

---
 drivers/xen/events/events_base.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

index 04ff194fecf42..d3b3fe4a5be4a 100644
@@ -1819,9 +1819,20 @@ static int xen_rebind_evtchn_to_cpu(struct irq_info *info, unsigned int tcpu)
 	 * virq or IPI channel, which don't actually need to be rebound. Ignore
 	 * it, but don't do the xenlinux-level rebind in that case.
 	 */
-	if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0)
+	if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_vcpu, &bind_vcpu) >= 0) {
+		int old_cpu = info->cpu;
+
 		bind_evtchn_to_cpu(evtchn, tcpu, false);
 
+		if (info->type == IRQT_VIRQ) {
+			int virq = info->u.virq;
+			int irq = per_cpu(virq_to_irq, old_cpu)[virq];
+
+			per_cpu(virq_to_irq, old_cpu)[virq] = -1;
+			per_cpu(virq_to_irq, tcpu)[virq] = irq;
+		}
+	}
+
 	do_unmask(info, EVT_MASK_REASON_TEMPORARY);
 
 	return 0;

2.51.0