[PATCH-for-4.17] xen/sched: fix restore_vcpu_affinity() by removing it

[Juergen Gross <jgross@xxxxxxxx>]

When the system is coming up after having been suspended,
restore_vcpu_affinity() is called for each domain in order to adjust
the vcpu's affinity settings in case a cpu didn't come to live again.

The way restore_vcpu_affinity() is doing that is wrong, because the
specific scheduler isn't being informed about a possible migration of
the vcpu to another cpu. Additionally the migration is often even
happening if all cpus are running again, as it is done without check
whether it is really needed.

As cpupool management is already calling cpu_disable_scheduler() for
cpus not having come up again, and cpu_disable_scheduler() is taking
care of eventually needed vcpu migration in the proper way, there is
simply no need for restore_vcpu_affinity().

So just remove restore_vcpu_affinity() completely.

Fixes: 8a5d50dd0b04 ("xen: sched: simplify ACPI S3 resume path.")
Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/acpi/power.c |  3 --
 xen/common/sched/core.c   | 70 ---------------------------------------
 xen/include/xen/sched.h   |  1 -
 3 files changed, 74 deletions(-)

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index 1bb4d78392..b76f673acb 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -159,10 +159,7 @@ static void thaw_domains(void)
 
     rcu_read_lock(&domlist_read_lock);
     for_each_domain ( d )
-    {
-        restore_vcpu_affinity(d);
         domain_unpause(d);
-    }
     rcu_read_unlock(&domlist_read_lock);
 }
 
diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index 83455fbde1..358fa077e3 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1196,76 +1196,6 @@ static void sched_reset_affinity_broken(const struct 
sched_unit *unit)
         v->affinity_broken = false;
 }
 
-void restore_vcpu_affinity(struct domain *d)
-{
-    unsigned int cpu = smp_processor_id();
-    struct sched_unit *unit;
-
-    ASSERT(system_state == SYS_STATE_resume);
-
-    rcu_read_lock(&sched_res_rculock);
-
-    for_each_sched_unit ( d, unit )
-    {
-        spinlock_t *lock;
-        unsigned int old_cpu = sched_unit_master(unit);
-        struct sched_resource *res;
-
-        ASSERT(!unit_runnable(unit));
-
-        /*
-         * Re-assign the initial processor as after resume we have no
-         * guarantee the old processor has come back to life again.
-         *
-         * Therefore, here, before actually unpausing the domains, we should
-         * set v->processor of each of their vCPUs to something that will
-         * make sense for the scheduler of the cpupool in which they are in.
-         */
-        lock = unit_schedule_lock_irq(unit);
-
-        cpumask_and(cpumask_scratch_cpu(cpu), unit->cpu_hard_affinity,
-                    cpupool_domain_master_cpumask(d));
-        if ( cpumask_empty(cpumask_scratch_cpu(cpu)) )
-        {
-            if ( sched_check_affinity_broken(unit) )
-            {
-                sched_set_affinity(unit, unit->cpu_hard_affinity_saved, NULL);
-                sched_reset_affinity_broken(unit);
-                cpumask_and(cpumask_scratch_cpu(cpu), unit->cpu_hard_affinity,
-                            cpupool_domain_master_cpumask(d));
-            }
-
-            if ( cpumask_empty(cpumask_scratch_cpu(cpu)) )
-            {
-                /* Affinity settings of one vcpu are for the complete unit. */
-                printk(XENLOG_DEBUG "Breaking affinity for %pv\n",
-                       unit->vcpu_list);
-                sched_set_affinity(unit, &cpumask_all, NULL);
-                cpumask_and(cpumask_scratch_cpu(cpu), unit->cpu_hard_affinity,
-                            cpupool_domain_master_cpumask(d));
-            }
-        }
-
-        res = get_sched_res(cpumask_any(cpumask_scratch_cpu(cpu)));
-        sched_set_res(unit, res);
-
-        spin_unlock_irq(lock);
-
-        /* v->processor might have changed, so reacquire the lock. */
-        lock = unit_schedule_lock_irq(unit);
-        res = sched_pick_resource(unit_scheduler(unit), unit);
-        sched_set_res(unit, res);
-        spin_unlock_irq(lock);
-
-        if ( old_cpu != sched_unit_master(unit) )
-            sched_move_irqs(unit);
-    }
-
-    rcu_read_unlock(&sched_res_rculock);
-
-    domain_update_node_affinity(d);
-}
-
 /*
  * This function is used by cpu_hotplug code via cpu notifier chain
  * and from cpupools to switch schedulers on a cpu.
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 557b3229f6..072e4846aa 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -1019,7 +1019,6 @@ void vcpu_set_periodic_timer(struct vcpu *v, s_time_t 
value);
 void sched_setup_dom0_vcpus(struct domain *d);
 int vcpu_temporary_affinity(struct vcpu *v, unsigned int cpu, uint8_t reason);
 int vcpu_set_hard_affinity(struct vcpu *v, const cpumask_t *affinity);
-void restore_vcpu_affinity(struct domain *d);
 int vcpu_affinity_domctl(struct domain *d, uint32_t cmd,
                          struct xen_domctl_vcpuaffinity *vcpuaff);
 
-- 
2.35.3