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Re: [Qemu-ppc] [PATCH] monitor: fix crash for platforms without a CPU 0
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-ppc] [PATCH] monitor: fix crash for platforms without a CPU 0 |
Date: |
Wed, 21 Sep 2016 09:14:02 -0300 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Wed, Sep 21, 2016 at 03:29:26PM +1000, David Gibson wrote:
> Now that we allow CPU hot unplug on a few platforms, we can end up in a
> situation where we don't have a CPU with index 0. Or at least we could,
> if we didn't have code to explicitly prohibit unplug of CPU 0.
>
> Longer term we want to allow CPU 0 unplug, this patch is an early step in
> allowing this, by removing an assumption in the monitor code that CPU 0
> always exists.
>
> Signed-off-by: Cédric Le Goater <address@hidden>
> [dwg: Rewrote commit message to better explain background]
> Signed-off-by: David Gibson <address@hidden>
> ---
> monitor.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Anyone want to volunteer to take this through their tree? If not, I
> can take it through my ppc tree.
>
> diff --git a/monitor.c b/monitor.c
> index 8bb8bbf..83c4edf 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -1025,7 +1025,7 @@ int monitor_set_cpu(int cpu_index)
> CPUState *mon_get_cpu(void)
> {
> if (!cur_mon->mon_cpu) {
> - monitor_set_cpu(0);
> + monitor_set_cpu(first_cpu->cpu_index);
So, we are replacing the "CPU 0 always exists" assumption with a
"first_cpu is always non-NULL" assumption.
But considering that the first_cpu assumption already exists
elsewhere and those cases can be found easily using grep, I think
this is OK. So:
Reviewed-by: Eduardo Habkost <address@hidden>
BTW, it is also possible to crash QEMU by unplugging the current
monitor CPU;
(qemu) device_add qemu64-x86_64-cpu,socket-id=2,core-id=0,thread-id=0,id=mycpu
(qemu) cpu 2
(qemu) device_del mycpu
(qemu) info registers
qemu:qemu_cpu_kick_thread: No such process
$
--
Eduardo