Re: [PULL 60/65] hw/acpi: Update ACPI `_STA` method with QOM vCPU ACPI Hotplug states

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 4 Nov 2024 16:09:26 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> From: Salil Mehta <salil.mehta@huawei.com>
> 
> Reflect the QOM vCPUs ACPI CPU hotplug states in the `_STA.Present` and
> and `_STA.Enabled` bits when the guest kernel evaluates the ACPI
> `_STA` method during initialization, as well as when vCPUs are
> hot-plugged or hot-unplugged. If the CPU is present then the its
> `enabled` status can be fetched using architecture-specific code [1].
> 
> Reference:
> [1] Example implementation of architecture-specific hook to fetch CPU
>     `enabled status
>     Link: https://github.com/salil-mehta/qemu/commit/c0b416b11e5af6505e558866f0eb6c9f3709173e
> 
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> Message-Id: <20241103102419.202225-4-salil.mehta@huawei.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  include/hw/core/cpu.h |  1 +
>  hw/acpi/cpu.c         | 38 ++++++++++++++++++++++++++++++++++----
>  2 files changed, 35 insertions(+), 4 deletions(-)
> 
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index e7de77dc6d..db8a6fbc6e 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -159,6 +159,7 @@ struct CPUClass {
>      void (*query_cpu_fast)(CPUState *cpu, CpuInfoFast *value);
>      int64_t (*get_arch_id)(CPUState *cpu);
>      bool (*cpu_persistent_status)(CPUState *cpu);
> +    bool (*cpu_enabled_status)(CPUState *cpu);
>      void (*set_pc)(CPUState *cpu, vaddr value);
>      vaddr (*get_pc)(CPUState *cpu);
>      int (*gdb_read_register)(CPUState *cpu, GByteArray *buf, int reg);
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index 9b03b4292e..23443f09a5 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -50,6 +50,18 @@ void acpi_cpu_ospm_status(CPUHotplugState *cpu_st, ACPIOSTInfoList ***list)
>      }
>  }
>  
> +static bool check_cpu_enabled_status(DeviceState *dev)
> +{
> +    CPUClass *k = dev ? CPU_GET_CLASS(dev) : NULL;
> +    CPUState *cpu = CPU(dev);
> +
> +    if (cpu && (!k->cpu_enabled_status || k->cpu_enabled_status(cpu))) {
> +        return true;
> +    }
> +
> +    return false;
> +}
> +
>  static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, unsigned size)
>  {
>      uint64_t val = 0;
> @@ -63,10 +75,11 @@ 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 |= check_cpu_enabled_status(DEVICE(cdev->cpu)) ? 1 : 0;
>          val |= cdev->is_inserting ? 2 : 0;
>          val |= cdev->is_removing  ? 4 : 0;
>          val |= cdev->fw_remove  ? 16 : 0;
> +        val |= cdev->cpu ? 32 : 0;
>          trace_cpuhp_acpi_read_flags(cpu_st->selector, val);
>          break;
>      case ACPI_CPU_CMD_DATA_OFFSET_RW:
> @@ -349,6 +362,7 @@ 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,
>                      build_madt_cpu_fn build_madt_cpu, hwaddr base_addr,
> @@ -409,7 +423,9 @@ 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);
>  
> @@ -439,6 +455,7 @@ 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);
> @@ -467,13 +484,26 @@ 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));

very likely this will break hotplug on after migration to older QEMU.

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