Backport of commit 3de218ff39b9e3f0d4

Backport of commit 3de218ff39b9e3f0d4

[Juergen Gross]

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Hi Greg,

the attached patch is a backport of upstream commit 3de218ff39b9e3f0d4
for Linux 5.10 and older (I've checked it to apply down to 4.4).


Juergen

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From 9535989b80d89932f34f7f1596b91b400d7adbb2 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Mon, 5 Jul 2021 13:12:27 +0200
Subject: [PATCH] xen/events: reset active flag for lateeoi events later

In order to avoid a race condition for user events when changing
cpu affinity reset the active flag only when EOI-ing the event.

This is working fine as all user events are lateeoi events. Note that
lateeoi_ack_mask_dynirq() is not modified as there is no explicit call
to xen_irq_lateeoi() expected later.

This is commit 3de218ff39b9e3f0d453fe3154f12a174de44b25 upstream.
Backport for Linux 5.10 and older.

Cc: stable@vger.kernel.org
Reported-by: Julien Grall <julien@xen.org>
Fixes: b6622798bc50b62 ("xen/events: avoid handling the same event on two 
cpus at the same time")
Tested-by: Julien Grall <julien@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrvsky@oracle.com>
Link: https://lore.kernel.org/r/20210623130913.9405-1-jgross@suse.com
---
 drivers/xen/events/events_base.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index 29bec0720514..af0f6ad32522 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -583,6 +583,9 @@ static void xen_irq_lateeoi_locked(struct irq_info *info, bool spurious)
 	}
 
 	info->eoi_time = 0;
+
+	/* is_active hasn't been reset yet, do it now. */
+	smp_store_release(&info->is_active, 0);
 	do_unmask(info, EVT_MASK_REASON_EOI_PENDING);
 }
 
@@ -1807,10 +1810,22 @@ static void lateeoi_ack_dynirq(struct irq_data *data)
 	struct irq_info *info = info_for_irq(data->irq);
 	evtchn_port_t evtchn = info ? info->evtchn : 0;
 
-	if (VALID_EVTCHN(evtchn)) {
-		do_mask(info, EVT_MASK_REASON_EOI_PENDING);
-		ack_dynirq(data);
-	}
+	if (!VALID_EVTCHN(evtchn))
+		return;
+
+	do_mask(info, EVT_MASK_REASON_EOI_PENDING);
+
+	if (unlikely(irqd_is_setaffinity_pending(data)) &&
+	    likely(!irqd_irq_disabled(data))) {
+		do_mask(info, EVT_MASK_REASON_TEMPORARY);
+
+		clear_evtchn(evtchn);
+
+		irq_move_masked_irq(data);
+
+		do_unmask(info, EVT_MASK_REASON_TEMPORARY);
+	} else
+		clear_evtchn(evtchn);
 }
 
 static void lateeoi_mask_ack_dynirq(struct irq_data *data)
-- 
2.26.2


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Re: Backport of commit 3de218ff39b9e3f0d4

[Greg Kroah-Hartman]

On Mon, Jul 05, 2021 at 01:58:09PM +0200, Juergen Gross wrote:
> Hi Greg,
> 
> the attached patch is a backport of upstream commit 3de218ff39b9e3f0d4
> for Linux 5.10 and older (I've checked it to apply down to 4.4).

Now applied, thanks.

greg k-h