xen/pvhsim: fix cpu onlining

Since commit 8d3c326f6756d1 ("xen: let vcpu_create() select processor")
the initial processor for all pv-shim vcpus will be 0, as no other cpus
are online when the vcpus are created. Before that commit the vcpus
would have processors set not being online yet, which worked just by
chance.

When the pv-shim vcpu becomes active it will have a hard affinity
not matching its initial processor assignment leading to failing
ASSERT()s or other problems depending on the selected scheduler.

Fix that by doing the affinity setting after onlining the cpu but
before taking the vcpu up. For vcpu 0 this is still in
sched_setup_dom0_vcpus(), for the other vcpus setting the affinity
there can be dropped.

Fixes: 8d3c326f6756d1 ("xen: let vcpu_create() select processor")
Reported-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Tested-by: Sergey Dyasli <sergey.dyasli@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: George Dunlap <george.dunlap@citrix.com>

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index 5edbcd9ac5f9af3662e121e33cc96a9475946c75..4329eaaefe722c9c15d28570db74ee4893d7a722 100644 (file)
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -837,6 +837,8 @@ long pv_shim_cpu_up(void *data)
                     v->vcpu_id, rc);
             return rc;
         }
+
+        vcpu_set_hard_affinity(v, cpumask_of(v->vcpu_id));
     }
 
     wake = test_and_clear_bit(_VPF_down, &v->pause_flags);

diff --git a/xen/common/schedule.c b/xen/common/schedule.c
index c327c40b921d5e21abe6b3bcee9a947fc9e11a10..e70cc70a65ac47dc7c6e914c427e6320f8d0ed3e 100644 (file)
--- a/xen/common/schedule.c
+++ b/xen/common/schedule.c
@@ -3102,13 +3102,17 @@ void __init sched_setup_dom0_vcpus(struct domain *d)
     for ( i = 1; i < d->max_vcpus; i++ )
         vcpu_create(d, i);
 
-    for_each_sched_unit ( d, unit )
+    /*
+     * PV-shim: vcpus are pinned 1:1.
+     * Initially only 1 cpu is online, others will be dealt with when
+     * onlining them. This avoids pinning a vcpu to a not yet online cpu here.
+     */
+    if ( pv_shim )
+        sched_set_affinity(d->vcpu[0]->sched_unit,
+                           cpumask_of(0), cpumask_of(0));
+    else
     {
-        unsigned int id = unit->unit_id;
-
-        if ( pv_shim )
-            sched_set_affinity(unit, cpumask_of(id), cpumask_of(id));
-        else
+        for_each_sched_unit ( d, unit )
         {
             if ( !opt_dom0_vcpus_pin && !dom0_affinity_relaxed )
                 sched_set_affinity(unit, &dom0_cpus, NULL);