>From 205b7622b84bc678f8a0d6ac121dff14439fe331 Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@xxxxxxxx>
To: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Cc: Wei Liu <wl@xxxxxxx>
Cc: "Roger Pau Monné" <roger.pau@xxxxxxxxxx>
Date: Tue, 22 Oct 2019 11:14:08 +0200
Subject: [PATCH] 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 redoing the affinity setting after onlining the cpu but
before taking the vcpu up.

Fixes: 8d3c326f6756d1 ("xen: let vcpu_create() select processor")
Reported-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/pv/shim.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index 5edbcd9ac5..4329eaaefe 100644
--- 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);
-- 
2.16.4