Laszlo Ersek writes:
> 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 <imamm...@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.
How about phrasing it to put the more general case first, e.g.
[0x8] Command data: (DWORD access, little endian)
The currently selected CPU, unless:
- The "CPU selector" value refers to an impossible CPU
- The "Command field" value last stored by the guest differs
from 0
In these last two cases, the value is 0.
>
> Thanks,
> Laszlo
--
Cheers,
Christophe de Dinechin (IRC c3d)
