Re: [Qemu-devel] [PATCH v3 10/19] pc: register created initial and hotpluged CPUs in one place pc_cpu_plug()

[Bandan Das]

Eduardo Habkost <address@hidden> writes:

> On Wed, Jul 13, 2016 at 06:59:21PM -0400, Bandan Das wrote:
>> Eduardo Habkost <address@hidden> writes:
>> 
>> > On Wed, Jul 13, 2016 at 06:32:27PM -0400, Bandan Das wrote:
>> >> Igor Mammedov <address@hidden> writes:
>> >> 
>> >> > consolidate possible_cpus array management in pc_cpu_plug()
>> >> > for smp_cpus, coldplugged with -device and hotplugged with
>> >> > device_add.
>> >> 
>> >> So, this takes care of the hotplug case and 09/19 took care of the
>> >> coldplug case, right ? If yes, we should probably modify this commit
>> >> message a little.
>> >
>> > This makes pc_cpu_plug() take care of both: now it will handle
>> > the coldplug case also (in addition to the hotplug case, that it
>> > already handled). I don't understand what you mean.
>> >
>> > Are you talking about the rtc_set_memory() call, only? This seems
>> > to be the only hotplug-specific code that still remains, in this
>> 
>> Right, I thought the rtc_set_memory() call in 09/19 takes care of the
>> case when the user boots with "-device" and this takes care of the case
>> when user invokes device_add, no ?
>
> Yes for rtc_set_memory(). But the main purpose of this patch is
> to reuse all the rest of pc_cpu_plug() (i.e. everything except
> for the rtc_set_memory() call) for the coldplug CPUs too.
>
> Note that I didn't review the patch completely, yet. The
> replacement for the possible_cpus code looks OK, but I didn't
> check if it is safe to call
> HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev)->plug() for coldplugged
> CPUs too.

Owing to "HOTPLUG_HANDLER_GET_CLASS" name, I think I incorrectly assumed that
pc_cpu_plug() is only invoked for the hotplug case. I understand the hotplug
cpu path which iiuc is via pc_hot_add_cpu()->realized->pc_cpu_plug but I am not
sure of "-device" case. I will take a closer look.

Anyway, if this patch takes care of both cases, the commit message makes sense.

Thanks,
Bandan


>> 
>> > patch.
>> >
>> >> 
>> >> Bandan
>> >> > Signed-off-by: Igor Mammedov <address@hidden>
>> >> > ---
>> >> >  hw/i386/pc.c | 25 +++++++++----------------
>> >> >  1 file changed, 9 insertions(+), 16 deletions(-)
>> >> >
>> >> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> >> > index 3206572..0f85b56 100644
>> >> > --- a/hw/i386/pc.c
>> >> > +++ b/hw/i386/pc.c
>> >> > @@ -1142,7 +1142,6 @@ void pc_cpus_init(PCMachineState *pcms)
>> >> >          if (i < smp_cpus) {
>> >> >              cpu = pc_new_cpu(typename, x86_cpu_apic_id_from_index(i),
>> >> >                               &error_fatal);
>> >> > -            pcms->possible_cpus->cpus[i].cpu = CPU(cpu);
>> >> >              object_unref(OBJECT(cpu));
>> >> >          }
>> >> >      }
>> >> > @@ -1697,25 +1696,19 @@ static void pc_cpu_plug(HotplugHandler 
>> >> > *hotplug_dev,
>> >> >      Error *local_err = NULL;
>> >> >      PCMachineState *pcms = PC_MACHINE(hotplug_dev);
>> >> >  
>> >> > -    if (!dev->hotplugged) {
>> >> > -        goto out;
>> >> > -    }
>> >> > -
>> >> > -    if (!pcms->acpi_dev) {
>> >> > -        error_setg(&local_err,
>> >> > -                   "cpu hotplug is not enabled: missing acpi device");
>> >> > -        goto out;
>> >> > +    if (pcms->acpi_dev) {
>> >> > +        hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
>> >> > +        hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
>> >> > +        if (local_err) {
>> >> > +            goto out;
>> >> > +        }
>> >> >      }
>> >> >  
>> >> > -    hhc = HOTPLUG_HANDLER_GET_CLASS(pcms->acpi_dev);
>> >> > -    hhc->plug(HOTPLUG_HANDLER(pcms->acpi_dev), dev, &local_err);
>> >> > -    if (local_err) {
>> >> > -        goto out;
>> >> > +    if (dev->hotplugged) {
>> >> > +        /* increment the number of CPUs */
>> >> > +        rtc_set_memory(pcms->rtc, 0x5f, rtc_get_memory(pcms->rtc, 
>> >> > 0x5f) + 1);
>> >> >      }
>> >> >  
>> >> > -    /* increment the number of CPUs */
>> >> > -    rtc_set_memory(pcms->rtc, 0x5f, rtc_get_memory(pcms->rtc, 0x5f) + 
>> >> > 1);
>> >> > -
>> >> >      found_cpu = pc_find_cpu_slot(pcms, CPU(dev), NULL);
>> >> >      found_cpu->cpu = CPU(dev);
>> >> >  out: