2020-05-08 22:13:27

by Boris Ostrovsky

Subject: [PATCH] xen/cpuhotplug: Fix initial CPU offlining for PV(H) guests

Commit a926f81d2f6c ("xen/cpuhotplug: Replace cpu_up/down() with
device_online/offline()") replaced cpu_down() with device_offline()
call which requires that the CPU has been registered before. This
registration, however, happens later from topology_init() which
is called as subsys_initcall(). setup_vcpu_hotplug_event(), on the
other hand, is invoked earlier, during arch_initcall().

As result, booting a PV(H) guest with vcpus < maxvcpus causes a crash.

Move setup_vcpu_hotplug_event() (and therefore setup_cpu_watcher()) to
late_initcall(). In addition, instead of performing all offlining steps
in setup_cpu_watcher() simply call disable_hotplug_cpu().

Fixes: a926f81d2f6c (xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()"
Signed-off-by: Boris Ostrovsky <[email protected]>
---
drivers/xen/cpu_hotplug.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
index ec975de..b96b11e 100644
--- a/drivers/xen/cpu_hotplug.c
+++ b/drivers/xen/cpu_hotplug.c
@@ -93,10 +93,8 @@ static int setup_cpu_watcher(struct notifier_block *notifier,
(void)register_xenbus_watch(&cpu_watch);

for_each_possible_cpu(cpu) {
- if (vcpu_online(cpu) == 0) {
- device_offline(get_cpu_device(cpu));
- set_cpu_present(cpu, false);
- }
+ if (vcpu_online(cpu) == 0)
+ disable_hotplug_cpu(cpu);
}

return NOTIFY_DONE;
@@ -119,5 +117,5 @@ static int __init setup_vcpu_hotplug_event(void)
return 0;
}

-arch_initcall(setup_vcpu_hotplug_event);
+late_initcall(setup_vcpu_hotplug_event);

--
1.8.3.1

2020-05-11 08:18:22

by Jürgen Groß

Subject: Re: [PATCH] xen/cpuhotplug: Fix initial CPU offlining for PV(H) guests

On 09.05.20 00:28, Boris Ostrovsky wrote:
> Commit a926f81d2f6c ("xen/cpuhotplug: Replace cpu_up/down() with
> device_online/offline()") replaced cpu_down() with device_offline()
> call which requires that the CPU has been registered before. This
> registration, however, happens later from topology_init() which
> is called as subsys_initcall(). setup_vcpu_hotplug_event(), on the
> other hand, is invoked earlier, during arch_initcall().
>
> As result, booting a PV(H) guest with vcpus < maxvcpus causes a crash.
>
> Move setup_vcpu_hotplug_event() (and therefore setup_cpu_watcher()) to
> late_initcall(). In addition, instead of performing all offlining steps
> in setup_cpu_watcher() simply call disable_hotplug_cpu().
>
> Fixes: a926f81d2f6c (xen/cpuhotplug: Replace cpu_up/down() with device_online/offline()"
> Signed-off-by: Boris Ostrovsky <[email protected]>

Reviewed-by: Juergen Gross <[email protected]>


Juergen