xen/sched: fix restore_vcpu_affinity() by removing it

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, together with the
no longer used sched_reset_affinity_broken().

Fixes: 8a04eaa8ea83 ("xen/sched: move some per-vcpu items to struct sched_unit")
Reported-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: Dario Faggioli <dfaggioli@suse.com>
Tested-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
master commit: fce1f381f7388daaa3e96dbb0d67d7a3e4bb2d2d
master date: 2022-10-24 11:16:27 +0100

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index dd397f713067661b5a8010ad52f83ac794d32047..1a7baeebe6d0fa550b465284fa2d5acd54c9fe01 100644 (file)
--- 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 900aab8f66a7c3bd2d1b881c3ebffe7b57e22bfa..9173cf690c72d35f4bdfc7ab637bed14c3b27557 100644 (file)
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -1188,84 +1188,6 @@ static bool sched_check_affinity_broken(const struct sched_unit *unit)
     return false;
 }
 
-static void sched_reset_affinity_broken(const struct sched_unit *unit)
-{
-    struct vcpu *v;
-
-    for_each_sched_unit_vcpu ( unit, v )
-        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 3f4225738a402ee7c6ef7c198021b079622e0c1e..1a1fab5239eccc272d9482cf4877daac3c3a69be 100644 (file)
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -999,7 +999,6 @@ 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);