Re: [Qemu-devel] [PATCH 1/5] acpi/cpu: add cpu hotplug callback function to match hotplug_handler API

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 11 Sep 2014 11:04:10 +0800
Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:

> Hi Igor,
> On 09/10/2014 09:28 PM, Igor Mammedov wrote:
> 
> > On Wed,  3 Sep 2014 17:06:13 +0800
> > Gu Zheng <guz.fnst@cn.fujitsu.com> wrote:
> > 
> >>
> >> Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
> >> ---
> >>  hw/acpi/cpu_hotplug.c         |   17 +++++++++++++++++
> >>  include/hw/acpi/cpu_hotplug.h |    3 +++
> >>  2 files changed, 20 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/hw/acpi/cpu_hotplug.c b/hw/acpi/cpu_hotplug.c
> >> index 2ad83a0..92c189b 100644
> >> --- a/hw/acpi/cpu_hotplug.c
> >> +++ b/hw/acpi/cpu_hotplug.c
> >> @@ -36,6 +36,23 @@ static const MemoryRegionOps AcpiCpuHotplug_ops = {
> >>      },
> >>  };
> >>  
> >> +void acpi_cpu_plug_cb(ACPIREGS *ar, qemu_irq irq,
> >> +                          AcpiCpuHotplug *g, DeviceState *dev)
> > wrong indentation ^^^
> > 
> > it wouldn't hurt to add errp argument here ...
> > 
> >> +{
> >> +    CPUState *cpu = CPU(dev);
> >> +    CPUClass *k = CPU_GET_CLASS(cpu);
> >> +    int64_t cpu_id;
> >> +
> >> +    ar->gpe.sts[0] |= ACPI_CPU_HOTPLUG_STATUS;
> >> +    cpu_id = k->get_arch_id(cpu);
> >> +    g_assert((cpu_id / 8) < ACPI_GPE_PROC_LEN);
> > ... and return error from here instead of aborting
> 
> Got it.
> 
> > 
> >> +    g->sts[cpu_id / 8] |= (1 << (cpu_id % 8));
> >> +
> >> +    acpi_update_sci(ar, irq);
> >> +
> >> +    cpu_resume(cpu);
> > Why are you adding cpu_resume() here?
> > check cpu_common_realizefn() which already does it.
> 
> Because hot added callback is called after cpu_common_realizefn(), so I moved
> cpu_resume(cpu) from cpu_common_realizefn() here to ensure the guest has already
> hot added cpu before we resume it.
cpu.realize() should create a fully working CPU and moving CPU internals to ACPI
is not correct. CPU hot-add shouyld not depend on whether guest OS supports it or not.

More over there is no need to resume CPU when guest OS hot-added it,
cpu.realize() creates secondary CPU in RESET state, so it does nothing and waits
for INIT/SIPI sequence (i.e. when guest OS decides to online CPU).

> 
> > 
> >> +}
> >> +
> >>  void AcpiCpuHotplug_add(ACPIGPE *gpe, AcpiCpuHotplug *g, CPUState *cpu)
> >>  {
> >>      CPUClass *k = CPU_GET_CLASS(cpu);
> >> diff --git a/include/hw/acpi/cpu_hotplug.h b/include/hw/acpi/cpu_hotplug.h
> >> index 9e5d30c..d025731 100644
> >> --- a/include/hw/acpi/cpu_hotplug.h
> >> +++ b/include/hw/acpi/cpu_hotplug.h
> >> @@ -20,6 +20,9 @@ typedef struct AcpiCpuHotplug {
> >>      uint8_t sts[ACPI_GPE_PROC_LEN];
> >>  } AcpiCpuHotplug;
> >>  
> >> +void acpi_cpu_plug_cb(ACPIREGS *ar, qemu_irq irq,
> >> +                          AcpiCpuHotplug *g, DeviceState *dev);
> > wrong indentation ^^^
> 
> OK, will fix this too.
> 
> Thanks,
> Gu
> 
> > 
> >> +
> >>  void AcpiCpuHotplug_add(ACPIGPE *gpe, AcpiCpuHotplug *g, CPUState *cpu);
> >>  
> >>  void AcpiCpuHotplug_init(MemoryRegion *parent, Object *owner,
> > 
> > 
> > .
> > 
> 
>