linux-kernel - [tip: irq/core] xen/events: Remove disfunct affinity spreading

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Date:   Sat, 12 Dec 2020 12:58:35 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, maz@...nel.org
Subject: [tip: irq/core] xen/events: Remove disfunct affinity spreading

The following commit has been merged into the irq/core branch of tip:

Commit-ID:     26599cd34323b73894ebcb5197693cdd668b4aa8
Gitweb:        https://git.kernel.org/tip/26599cd34323b73894ebcb5197693cdd668b4aa8
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Thu, 10 Dec 2020 20:26:01 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Sat, 12 Dec 2020 12:59:06 +01:00

xen/events: Remove disfunct affinity spreading

This function can only ever work when the event channels:

  - are already established
  - interrupts assigned to them
  - the affinity has been set by user space already

because any newly set up event channel is forced to be bound to CPU0 and
the affinity mask of the interrupt is forced to contain cpumask_of(0).

As the CPU0 enforcement was in place _before_ this was implemented it's
entirely unclear how that can ever have worked at all.

Remove it as preparation for doing it proper.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Link: https://lore.kernel.org/r/20201210194045.065115500@linutronix.de

---
 drivers/xen/events/events_base.c |  9 +--------
 drivers/xen/evtchn.c             | 34 +-------------------------------
 2 files changed, 1 insertion(+), 42 deletions(-)

diff --git a/drivers/xen/events/events_base.c b/drivers/xen/events/events_base.c
index d6458e4..9cade19 100644
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -1696,15 +1696,6 @@ static int set_affinity_irq(struct irq_data *data, const struct cpumask *dest,
 	return ret;
 }
 
-/* To be called with desc->lock held. */
-int xen_set_affinity_evtchn(struct irq_desc *desc, unsigned int tcpu)
-{
-	struct irq_data *d = irq_desc_get_irq_data(desc);
-
-	return set_affinity_irq(d, cpumask_of(tcpu), false);
-}
-EXPORT_SYMBOL_GPL(xen_set_affinity_evtchn);
-
 static void enable_dynirq(struct irq_data *data)
 {
 	evtchn_port_t evtchn = evtchn_from_irq(data->irq);
diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c
index 5dc016d..a7a8571 100644
--- a/drivers/xen/evtchn.c
+++ b/drivers/xen/evtchn.c
@@ -421,36 +421,6 @@ static void evtchn_unbind_from_user(struct per_user_data *u,
 	del_evtchn(u, evtchn);
 }
 
-static DEFINE_PER_CPU(int, bind_last_selected_cpu);
-
-static void evtchn_bind_interdom_next_vcpu(evtchn_port_t evtchn)
-{
-	unsigned int selected_cpu, irq;
-	struct irq_desc *desc;
-	unsigned long flags;
-
-	irq = irq_from_evtchn(evtchn);
-	desc = irq_to_desc(irq);
-
-	if (!desc)
-		return;
-
-	raw_spin_lock_irqsave(&desc->lock, flags);
-	selected_cpu = this_cpu_read(bind_last_selected_cpu);
-	selected_cpu = cpumask_next_and(selected_cpu,
-			desc->irq_common_data.affinity, cpu_online_mask);
-
-	if (unlikely(selected_cpu >= nr_cpu_ids))
-		selected_cpu = cpumask_first_and(desc->irq_common_data.affinity,
-				cpu_online_mask);
-
-	this_cpu_write(bind_last_selected_cpu, selected_cpu);
-
-	/* unmask expects irqs to be disabled */
-	xen_set_affinity_evtchn(desc, selected_cpu);
-	raw_spin_unlock_irqrestore(&desc->lock, flags);
-}
-
 static long evtchn_ioctl(struct file *file,
 			 unsigned int cmd, unsigned long arg)
 {
@@ -508,10 +478,8 @@ static long evtchn_ioctl(struct file *file,
 			break;
 
 		rc = evtchn_bind_to_user(u, bind_interdomain.local_port);
-		if (rc == 0) {
+		if (rc == 0)
 			rc = bind_interdomain.local_port;
-			evtchn_bind_interdom_next_vcpu(rc);
-		}
 		break;
 	}