Re: [PATCH for-5.0 v2 9/9] acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command

[Laszlo Ersek]

On 12/09/19 14:09, Igor Mammedov wrote:
> Firmware can enumerate present at boot APs by broadcasting wakeup IPI,
> so that woken up secondary CPUs could register them-selves.
> However in CPU hotplug case, it would need to know architecture
> specific CPU IDs for possible and hotplugged CPUs so it could
> prepare environment for and wake hotplugged AP.
> 
> Reuse and extend existing CPU hotplug interface to return architecture
> specific ID for currently selected CPU in 2 registers:
>  - lower 32 bits in ACPI_CPU_CMD_DATA_OFFSET_RW
>  - upper 32 bits in ACPI_CPU_CMD_DATA2_OFFSET_R
> 
> On x86, firmware will use CPHP_GET_CPU_ID_CMD for fetching the APIC ID
> when handling hotplug SMI.
> 
> Later, CPHP_GET_CPU_ID_CMD will be used on ARM to retrieve MPIDR,
> which serves the similar to APIC ID purpose.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
> v1:
>  - s/ACPI_CPU_CMD_DATA2_OFFSET_RW/ACPI_CPU_CMD_DATA2_OFFSET_R/.
> v2:
>  - ACPI_CPU_CMD_DATA2_OFFSET_R moved into separate patch
>    that adds 'Command data 2' field separately
>  - ammend commit message
> ---
>  docs/specs/acpi_cpu_hotplug.txt | 3 +++
>  hw/acpi/cpu.c                   | 7 +++++++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
> index cb99cf3..a8ce5e7 100644
> --- a/docs/specs/acpi_cpu_hotplug.txt
> +++ b/docs/specs/acpi_cpu_hotplug.txt
> @@ -47,6 +47,7 @@ read access:
>      [0x0-0x3] Command data 2: (DWORD access)
>                if value last stored in 'Command field':
>                  0: reads as 0x0
> +                3: upper 32 bits of architecture specific CPU ID value
>                  other values: reserved
>      [0x4] CPU device status fields: (1 byte access)
>          bits:
> @@ -61,6 +62,8 @@ read access:
>      [0x8] Command data: (DWORD access)
>            contains 0 unless value last stored in 'Command field' is one of:
>                0: contains 'CPU selector' value of a CPU with pending event[s]
> +              3: lower 32 bits of architecture specific CPU ID value
> +                 (in x86 case: APIC ID)
>  
>  write access:
>      offset:
> diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
> index d475c06..e2c957c 100644
> --- a/hw/acpi/cpu.c
> +++ b/hw/acpi/cpu.c
> @@ -18,6 +18,7 @@ enum {
>      CPHP_GET_NEXT_CPU_WITH_EVENT_CMD = 0,
>      CPHP_OST_EVENT_CMD = 1,
>      CPHP_OST_STATUS_CMD = 2,
> +    CPHP_GET_CPU_ID_CMD = 3,
>      CPHP_CMD_MAX
>  };
>  
> @@ -75,6 +76,9 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
> unsigned size)
>          case CPHP_GET_NEXT_CPU_WITH_EVENT_CMD:
>             val = cpu_st->selector;
>             break;
> +        case CPHP_GET_CPU_ID_CMD:
> +           val = cdev->arch_id & 0xFFFFFFFF;
> +           break;
>          default:
>             break;
>          }
> @@ -85,6 +89,9 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
> unsigned size)
>          case CPHP_GET_NEXT_CPU_WITH_EVENT_CMD:
>             val = 0;
>             break;
> +        case CPHP_GET_CPU_ID_CMD:
> +           val = cdev->arch_id >> 32;
> +           break;
>          default:
>             break;
>          }
> 

Reviewed-by: Laszlo Ersek <address@hidden>

Thanks!
Laszlo