Re: [PATCH RFC V2 19/37] hw/acpi: ACPI/AML Changes to reflect the correct _STA.{PRES, ENA} Bits to Guest

[Jonathan Cameron]

On Tue, 26 Sep 2023 11:04:18 +0100
Salil Mehta via <qemu-devel@nongnu.org> wrote:

> ACPI AML changes to properly reflect the _STA.PRES and _STA.ENA Bits to the
> guest during initialzation, when CPUs are hotplugged and after CPUs are
> hot-unplugged.
> 
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>

Hi Salil,

Just brought up a qemu on qemu test setup again to poke
the kernel series and hopefully resolve a few questions there.
Ran into a trivial problem in which the kernel was trying and
failing to attach an ACPI handler before these were hotplugged.
Came down to the kernel code now treating functional in _STA as
meaning can be enumerated and effectively
ignoring all the other bits.

Requires a change to the value presented by default...
See below.  Fix may well be completely wrong even though it works ;)

Thanks,

Jonathan

> ---
>  hw/acpi/cpu.c                  | 49 +++++++++++++++++++++++++++++++---
>  hw/acpi/generic_event_device.c | 11 ++++++++
>  include/hw/acpi/cpu.h          |  2 ++
>  3 files changed, 58 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index 232720992d..e1299696d3 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -63,10 +63,11 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
> unsigned size)
>      cdev = &cpu_st->devs[cpu_st->selector];
>      switch (addr) {
>      case ACPI_CPU_FLAGS_OFFSET_RW: /* pack and return is_* fields */
> -        val |= cdev->cpu ? 1 : 0;
> +        val |= cdev->is_enabled ? 1 : 0;
>          val |= cdev->is_inserting ? 2 : 0;
>          val |= cdev->is_removing  ? 4 : 0;
>          val |= cdev->fw_remove  ? 16 : 0;
> +        val |= cdev->is_present ? 32 : 0;
>          trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
>          break;
>      case ACPI_CPU_CMD_DATA_OFFSET_RW:
> @@ -228,7 +229,21 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
>          struct CPUState *cpu = CPU(id_list->cpus[i].cpu);
>          if (qemu_present_cpu(cpu)) {
>              state->devs[i].cpu = cpu;
> +            state->devs[i].is_present = true;
> +        } else {
> +            if (qemu_persistent_cpu(cpu)) {
> +                state->devs[i].is_present = true;
> +            } else {
> +                state->devs[i].is_present = false;
> +            }
>          }
> +
> +        if (qemu_enabled_cpu(cpu)) {
> +            state->devs[i].is_enabled = true;
> +        } else {
> +            state->devs[i].is_enabled = false;
> +        }
> +
>          state->devs[i].arch_id = id_list->cpus[i].arch_id;
>      }
>      memory_region_init_io(&state->ctrl_reg, owner, &cpu_hotplug_ops, state,
> @@ -261,6 +276,8 @@ void acpi_cpu_plug_cb(HotplugHandler *hotplug_dev,
>      }
>  
>      cdev->cpu = CPU(dev);
> +    cdev->is_present = true;
> +    cdev->is_enabled = true;
>      if (dev->hotplugged) {
>          cdev->is_inserting = true;
>          acpi_send_event(DEVICE(hotplug_dev), ACPI_CPU_HOTPLUG_STATUS);
> @@ -292,6 +309,11 @@ void acpi_cpu_unplug_cb(CPUHotplugState *cpu_st,
>          return;
>      }
>  
> +    cdev->is_enabled = false;
> +    if (!qemu_persistent_cpu(CPU(dev))) {
> +        cdev->is_present = false;
> +    }
> +
>      cdev->cpu = NULL;
>  }
>  
> @@ -302,6 +324,8 @@ static const VMStateDescription vmstate_cpuhp_sts = {
>      .fields      = (VMStateField[]) {
>          VMSTATE_BOOL(is_inserting, AcpiCpuStatus),
>          VMSTATE_BOOL(is_removing, AcpiCpuStatus),
> +        VMSTATE_BOOL(is_present, AcpiCpuStatus),
> +        VMSTATE_BOOL(is_enabled, AcpiCpuStatus),
>          VMSTATE_UINT32(ost_event, AcpiCpuStatus),
>          VMSTATE_UINT32(ost_status, AcpiCpuStatus),
>          VMSTATE_END_OF_LIST()
> @@ -339,6 +363,7 @@ const VMStateDescription vmstate_cpu_hotplug = {
>  #define CPU_REMOVE_EVENT  "CRMV"
>  #define CPU_EJECT_EVENT   "CEJ0"
>  #define CPU_FW_EJECT_EVENT "CEJF"
> +#define CPU_PRESENT       "CPRS"
>  
>  void build_cpus_aml(Aml *table, MachineState *machine, CPUHotplugFeatures 
> opts,
>                      hwaddr base_addr,
> @@ -399,7 +424,9 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> CPUHotplugFeatures opts,
>          aml_append(field, aml_named_field(CPU_EJECT_EVENT, 1));
>          /* tell firmware to do device eject, write only */
>          aml_append(field, aml_named_field(CPU_FW_EJECT_EVENT, 1));
> -        aml_append(field, aml_reserved_field(3));
> +        /* 1 if present, read only */
> +        aml_append(field, aml_named_field(CPU_PRESENT, 1));
> +        aml_append(field, aml_reserved_field(2));
>          aml_append(field, aml_named_field(CPU_COMMAND, 8));
>          aml_append(cpu_ctrl_dev, field);
>  
> @@ -429,6 +456,7 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> CPUHotplugFeatures opts,
>          Aml *ctrl_lock = aml_name("%s.%s", cphp_res_path, CPU_LOCK);
>          Aml *cpu_selector = aml_name("%s.%s", cphp_res_path, CPU_SELECTOR);
>          Aml *is_enabled = aml_name("%s.%s", cphp_res_path, CPU_ENABLED);
> +        Aml *is_present = aml_name("%s.%s", cphp_res_path, CPU_PRESENT);
>          Aml *cpu_cmd = aml_name("%s.%s", cphp_res_path, CPU_COMMAND);
>          Aml *cpu_data = aml_name("%s.%s", cphp_res_path, CPU_DATA);
>          Aml *ins_evt = aml_name("%s.%s", cphp_res_path, CPU_INSERT_EVENT);
> @@ -457,13 +485,26 @@ void build_cpus_aml(Aml *table, MachineState *machine, 
> CPUHotplugFeatures opts,
>          {
>              Aml *idx = aml_arg(0);
>              Aml *sta = aml_local(0);
> +            Aml *ifctx2;
> +            Aml *else_ctx;
>  
>              aml_append(method, aml_acquire(ctrl_lock, 0xFFFF));
>              aml_append(method, aml_store(idx, cpu_selector));
>              aml_append(method, aml_store(zero, sta));
> -            ifctx = aml_if(aml_equal(is_enabled, one));
> +            ifctx = aml_if(aml_equal(is_present, one));
>              {
> -                aml_append(ifctx, aml_store(aml_int(0xF), sta));
> +                ifctx2 = aml_if(aml_equal(is_enabled, one));
> +                {
> +                    /* cpu is present and enabled */
> +                    aml_append(ifctx2, aml_store(aml_int(0xF), sta));
> +                }
> +                aml_append(ifctx, ifctx2);
> +                else_ctx = aml_else();
> +                {
> +                    /* cpu is present but disabled */
> +                    aml_append(else_ctx, aml_store(aml_int(0xD), sta));
For the current kernel patches, functional should not be set. So this should
be something like 0x5.

> +                }
> +                aml_append(ifctx, else_ctx);
>              }
>              aml_append(method, ifctx);
>              aml_append(method, aml_release(ctrl_lock));