Re: [RFC 1/3] acpi: cpuhp: fix 'Command data' description is spec

[Laszlo Ersek <lersek@redhat.com>]

On 10/10/19 15:31, Laszlo Ersek wrote:
> 2nd round:
> 
> On 10/09/19 15:22, Igor Mammedov wrote:
>> QEMU returns 0, in case of erro or invalid value in 'Command field',
>> make spec match reality, i.e.
> 
> AHA! so this is exactly where you meant to list the particular cases
> when "command data" reads as 0:
> - CPU >= max_cpus selected,
> - CPU with pending events asked for, but none found
> 
>> Also fix returned value description  in case 'Command field' == 0x0,
>> it's in not PXM but CPU selector value with pending event
>>
>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>> ---
>>  docs/specs/acpi_cpu_hotplug.txt | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/docs/specs/acpi_cpu_hotplug.txt b/docs/specs/acpi_cpu_hotplug.txt
>> index ee219c8358..ac5903b2b1 100644
>> --- a/docs/specs/acpi_cpu_hotplug.txt
>> +++ b/docs/specs/acpi_cpu_hotplug.txt
>> @@ -44,9 +44,10 @@ read access:
>>             3-7: reserved and should be ignored by OSPM
>>      [0x5-0x7] reserved
>>      [0x8] Command data: (DWORD access)
>> -          in case of error or unsupported command reads is 0xFFFFFFFF
>> +          in case of error or unsupported command reads is 0x0
>>            current 'Command field' value:
>> -              0: returns PXM value corresponding to device
>> +              0: returns CPU selector value corresponding to a CPU with
>> +                 pending event.
>>  
>>  write access:
>>      offset:
>>
> 
> How about:
> 
>     [0x8] Command data: (DWORD access, little endian)
>           If the "CPU selector" value last stored by the guest refers to
>           an impossible CPU, then 0.
>           Otherwise, if the "Command field" value last stored by the
>           guest differs from 0, then 0.
>           Otherwise, if there is at least one CPU with a pending event,
>           then that CPU has been selected; the command data register
>           returns that selector.
>           Otherwise, 0.

Hmmm not exactly. Let me try again.

    [0x8] Command data: (DWORD access, little endian)
          If the "CPU selector" value last stored by the guest refers to
          an impossible CPU, then 0.
          Otherwise, if the "Command field" value last stored by the
          guest differs from 0, then 0.
          Otherwise, the currently selected CPU.

Thanks,
Laszlo