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Tsirkin" , Gerd Hoffmann , Igor Mammedov , Paolo Bonzini , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" (I've been dropped from the address list, not sure why) On 10/22/19 19:17, Christophe de Dinechin wrote: >=20 > Laszlo Ersek writes: >=20 >> 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 >=3D max_cpus selected, >>> - CPU with pending events asked for, but none found >>> >>>> Also fix returned value description in case 'Command field' =3D=3D 0x= 0, >>>> it's in not PXM but CPU selector value with pending event >>>> >>>> Signed-off-by: Igor Mammedov >>>> --- >>>> 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_hot= plug.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 wi= th >>>> + 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 t= o >>> 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. >=20 > How about phrasing it to put the more general case first, e.g. >=20 > [0x8] Command data: (DWORD access, little endian) >=20 > 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. I prefer my proposal because it translates to source code more directly (a ladder of "if / else" pairs, or similar). (I know that some programming languages support "unless"; I could never wrap my brain around that idea! :) ) Thanks Laszlo