RE: [PATCH V15 3/7] hw/acpi: Update ACPI GED framework to support vCPU Hotplug

[Salil Mehta]

Hi Igor,

Thanks for the feedback.

>  From: qemu-arm-bounces+salil.mehta=huawei.com@nongnu.org <qemu-
>  arm-bounces+salil.mehta=huawei.com@nongnu.org> On Behalf Of Igor
>  Mammedov
>  Sent: Monday, July 15, 2024 2:12 PM
>  To: Salil Mehta <salil.mehta@huawei.com>
>  
>  On Sat, 13 Jul 2024 19:25:12 +0100
>  Salil Mehta <salil.mehta@huawei.com> wrote:
>  
>  > ACPI GED (as described in the ACPI 6.4 spec) uses an interrupt listed
>  > in the _CRS object of GED to intimate OSPM about an event. Later then
>  > demultiplexes the notified event by evaluating ACPI _EVT method to
>  > know the type of event. Use ACPI GED to also notify the guest kernel
>  about any CPU hot(un)plug events.
>  >
>  > Note, GED interface is used by many hotplug events like memory
>  > hotplug, NVDIMM hotplug and non-hotplug events like system power
>  down
>  > event. Each of these can be selected using a bit in the 32 bit GED IO
>  > interface. A bit has been reserved for the CPU hotplug event.
>  
>  > ACPI CPU hotplug related initialization should only happen if
>  > ACPI_CPU_HOTPLUG support has been enabled for particular
>  architecture.
>  > Add cpu_hotplug_hw_init() stub to avoid compilation break.
>  
>  so any target (and machines in it) that has ACPI_CPU_HOTPLUG enabled will
>  use have all CPU hotplug machinery builtin which is fine.
>  
>  However any machine that uses GED but do not opt-in into CPU hotplug, will
>  still have CPU hotplug registers/memory regions enabled/mapped.
>  
>  It's not much concern for upstream as migration from new to older QEMU is
>  not supported, however it will break migration downstream (arm/virt) as
>  new QEMU will try to migrate memory regions/state that do not exists in
>  older QEMU. Se below for suggestion.


Sorry. I missed this one. Yes. agreed.


>  > Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
>  > Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
>  > Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
>  > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>  > Reviewed-by: Gavin Shan <gshan@redhat.com>
>  > Reviewed-by: David Hildenbrand <david@redhat.com>
>  > Reviewed-by: Shaoqin Huang <shahuang@redhat.com>
>  > Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
>  > Tested-by: Xianglai Li <lixianglai@loongson.cn>
>  > Tested-by: Miguel Luis <miguel.luis@oracle.com>
>  > Reviewed-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
>  > Tested-by: Zhao Liu <zhao1.liu@intel.com>
>  > Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
>  > ---
>  >  docs/specs/acpi_hw_reduced_hotplug.rst |  3 ++-
>  >  hw/acpi/acpi-cpu-hotplug-stub.c        |  6 ++++++
>  >  hw/acpi/generic_event_device.c         | 24 ++++++++++++++++++++++++
>  >  include/hw/acpi/generic_event_device.h |  4 ++++
>  >  4 files changed, 36 insertions(+), 1 deletion(-)
>  >
>  > diff --git a/docs/specs/acpi_hw_reduced_hotplug.rst
>  > b/docs/specs/acpi_hw_reduced_hotplug.rst
>  > index 0bd3f9399f..3acd6fcd8b 100644
>  > --- a/docs/specs/acpi_hw_reduced_hotplug.rst
>  > +++ b/docs/specs/acpi_hw_reduced_hotplug.rst
>  > @@ -64,7 +64,8 @@ GED IO interface (4 byte access)
>  >         0: Memory hotplug event
>  >         1: System power down event
>  >         2: NVDIMM hotplug event
>  > -    3-31: Reserved
>  > +       3: CPU hotplug event
>  > +    4-31: Reserved
>  >
>  >  **write_access:**
>  >
>  > diff --git a/hw/acpi/acpi-cpu-hotplug-stub.c
>  > b/hw/acpi/acpi-cpu-hotplug-stub.c index 3fc4b14c26..c6c61bb9cd 100644
>  > --- a/hw/acpi/acpi-cpu-hotplug-stub.c
>  > +++ b/hw/acpi/acpi-cpu-hotplug-stub.c
>  > @@ -19,6 +19,12 @@ void legacy_acpi_cpu_hotplug_init(MemoryRegion
>  *parent, Object *owner,
>  >      return;
>  >  }
>  >
>  > +void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
>  > +                         CPUHotplugState *state, hwaddr base_addr) {
>  > +    return;
>  > +}
>  > +
>  >  void acpi_cpu_ospm_status(CPUHotplugState *cpu_st, ACPIOSTInfoList
>  > ***list)  {
>  >      return;
>  > diff --git a/hw/acpi/generic_event_device.c
>  > b/hw/acpi/generic_event_device.c index 2d6e91b124..1b31d633ba
>  100644
>  > --- a/hw/acpi/generic_event_device.c
>  > +++ b/hw/acpi/generic_event_device.c
>  > @@ -25,6 +25,7 @@ static const uint32_t ged_supported_events[] = {
>  >      ACPI_GED_MEM_HOTPLUG_EVT,
>  >      ACPI_GED_PWR_DOWN_EVT,
>  >      ACPI_GED_NVDIMM_HOTPLUG_EVT,
>  > +    ACPI_GED_CPU_HOTPLUG_EVT,
>  >  };
>  >
>  >  /*
>  > @@ -234,6 +235,8 @@ static void
>  acpi_ged_device_plug_cb(HotplugHandler *hotplug_dev,
>  >          } else {
>  >              acpi_memory_plug_cb(hotplug_dev, &s->memhp_state, dev,
>  errp);
>  >          }
>  > +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>  > +        acpi_cpu_plug_cb(hotplug_dev, &s->cpuhp_state, dev, errp);
>  >      } else {
>  >          error_setg(errp, "virt: device plug request for unsupported 
> device"
>  >                     " type: %s", object_get_typename(OBJECT(dev)));
>  > @@ -248,6 +251,8 @@ static void
>  acpi_ged_unplug_request_cb(HotplugHandler *hotplug_dev,
>  >      if ((object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM) &&
>  >                         !(object_dynamic_cast(OBJECT(dev), TYPE_NVDIMM)))) 
> {
>  >          acpi_memory_unplug_request_cb(hotplug_dev, &s->memhp_state,
>  > dev, errp);
>  > +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>  > +        acpi_cpu_unplug_request_cb(hotplug_dev, &s->cpuhp_state, dev,
>  > + errp);
>  >      } else {
>  >          error_setg(errp, "acpi: device unplug request for unsupported
>  device"
>  >                     " type: %s", object_get_typename(OBJECT(dev)));
>  > @@ -261,6 +266,8 @@ static void acpi_ged_unplug_cb(HotplugHandler
>  > *hotplug_dev,
>  >
>  >      if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
>  >          acpi_memory_unplug_cb(&s->memhp_state, dev, errp);
>  > +    } else if (object_dynamic_cast(OBJECT(dev), TYPE_CPU)) {
>  > +        acpi_cpu_unplug_cb(&s->cpuhp_state, dev, errp);
>  >      } else {
>  >          error_setg(errp, "acpi: device unplug for unsupported device"
>  >                     " type: %s", object_get_typename(OBJECT(dev)));
>  > @@ -272,6 +279,7 @@ static void acpi_ged_ospm_status(AcpiDeviceIf
>  *adev, ACPIOSTInfoList ***list)
>  >      AcpiGedState *s = ACPI_GED(adev);
>  >
>  >      acpi_memory_ospm_status(&s->memhp_state, list);
>  > +    acpi_cpu_ospm_status(&s->cpuhp_state, list);
>  >  }
>  >
>  >  static void acpi_ged_send_event(AcpiDeviceIf *adev,
>  > AcpiEventStatusBits ev) @@ -286,6 +294,8 @@ static void
>  acpi_ged_send_event(AcpiDeviceIf *adev, AcpiEventStatusBits ev)
>  >          sel = ACPI_GED_PWR_DOWN_EVT;
>  >      } else if (ev & ACPI_NVDIMM_HOTPLUG_STATUS) {
>  >          sel = ACPI_GED_NVDIMM_HOTPLUG_EVT;
>  > +    } else if (ev & ACPI_CPU_HOTPLUG_STATUS) {
>  > +        sel = ACPI_GED_CPU_HOTPLUG_EVT;
>  >      } else {
>  >          /* Unknown event. Return without generating interrupt. */
>  >          warn_report("GED: Unsupported event %d. No irq injected",
>  > ev); @@ -371,6 +381,19 @@ static const VMStateDescription
>  vmstate_acpi_ged = {
>  >      }
>  >  };
>  >
>  > +static void acpi_ged_realize(DeviceState *dev, Error **errp) {
>  > +    AcpiGedState *s = ACPI_GED(dev);
>  > +    SysBusDevice *sbd = SYS_BUS_DEVICE(dev);
>  > +
>  
>  > +    /* initialize CPU Hotplug related regions */
>  > +    memory_region_init(&s->container_cpuhp, OBJECT(dev), "cpuhp
>  container",
>  > +                       ACPI_CPU_HOTPLUG_REG_LEN);
>  > +    sysbus_init_mmio(sbd, &s->container_cpuhp);
>  > +    cpu_hotplug_hw_init(&s->container_cpuhp, OBJECT(dev),
>  > +                        &s->cpuhp_state, 0);
>  
>  how about making it conditional on supported events see hw/arm/virt.c:
>  create_acpi_ged()
>      if (ms->ram_slots) {
>          event |= ACPI_GED_MEM_HOTPLUG_EVT;
>      }
>  
>      if (ms->nvdimms_state->is_enabled) {
>          event |= ACPI_GED_NVDIMM_HOTPLUG_EVT;
>      }
>  
>  so cpu hotplug would have similar section and ged realize could use ged-
>  event to enable/disable cpuhp feature registers and hwinit.


Got it, thanks for pointing out. I will fix this and share V16 by COB today 
itself.


Best regards
Salil.


>  
>  > +}
>  > +
>  >  static void acpi_ged_initfn(Object *obj)  {
>  >      DeviceState *dev = DEVICE(obj);
>  > @@ -411,6 +434,7 @@ static void acpi_ged_class_init(ObjectClass *class,
>  void *data)
>  >      dc->desc = "ACPI Generic Event Device";
>  >      device_class_set_props(dc, acpi_ged_properties);
>  >      dc->vmsd = &vmstate_acpi_ged;
>  > +    dc->realize = acpi_ged_realize;
>  >
>  >      hc->plug = acpi_ged_device_plug_cb;
>  >      hc->unplug_request = acpi_ged_unplug_request_cb; diff --git
>  > a/include/hw/acpi/generic_event_device.h
>  > b/include/hw/acpi/generic_event_device.h
>  > index ba84ce0214..e091ac2108 100644
>  > --- a/include/hw/acpi/generic_event_device.h
>  > +++ b/include/hw/acpi/generic_event_device.h
>  > @@ -62,6 +62,7 @@
>  >  #include "hw/sysbus.h"
>  >  #include "hw/acpi/memory_hotplug.h"
>  >  #include "hw/acpi/ghes.h"
>  > +#include "hw/acpi/cpu.h"
>  >  #include "qom/object.h"
>  >
>  >  #define ACPI_POWER_BUTTON_DEVICE "PWRB"
>  > @@ -95,6 +96,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(AcpiGedState,
>  ACPI_GED)
>  >  #define ACPI_GED_MEM_HOTPLUG_EVT   0x1
>  >  #define ACPI_GED_PWR_DOWN_EVT      0x2
>  >  #define ACPI_GED_NVDIMM_HOTPLUG_EVT 0x4
>  > +#define ACPI_GED_CPU_HOTPLUG_EVT    0x8
>  >
>  >  typedef struct GEDState {
>  >      MemoryRegion evt;
>  > @@ -106,6 +108,8 @@ struct AcpiGedState {
>  >      SysBusDevice parent_obj;
>  >      MemHotplugState memhp_state;
>  >      MemoryRegion container_memhp;
>  > +    CPUHotplugState cpuhp_state;
>  > +    MemoryRegion container_cpuhp;
>  >      GEDState ged_state;
>  >      uint32_t ged_event_bitmap;
>  >      qemu_irq irq;
>