Re: [Xen-devel] [RFC PATCH 3/5] Tool/ACPI: DSDT extension to support more vcpus

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

On 2017年08月25日 20:01, Jan Beulich wrote:
>>>> On 25.08.17 at 12:36, <roger.pau@xxxxxxxxxx> wrote:
>> On Thu, Aug 24, 2017 at 10:52:18PM -0400, Lan Tianyu wrote:
>>> This patch is to change DSDT table for processor object to support >255 
>> vcpus.
>>
>> The note in ACPI 6.1A spec section 5.2.12.12 contains the following:
>>
>> [Compatibility note] On some legacy OSes, Logical processors with APIC
>> ID values less than 255 (whether in XAPIC or X2APIC mode) must use the
>> Processor Local APIC structure to convey their APIC information to
>> OSPM, and those processors must be declared in the DSDT using the
>> Processor() keyword. Logical processors with APIC ID values 255 and
>> greater must use the Processor Local x2APIC structure and be declared
>> using the Device() keyword. See Section 19.6.102 "Processor (Declare
>> Processor)" for more information.
>>
>> So you cannot unconditionally switch to using the Device for all
>> processors.
>>
>> vCPUs <= 128 need to use the Processor keyword, while vCPUs > 128 need
>> to use the Device keyword.
> 
> While changing this code, may I suggest to stop referring to the
> 128 vCPU boundary? The decision should be solely based on
> LAPIC ID, such that the only place to change later on will end up
> being the one where it gets set to double the vCPU number.
> 

OK. Got it.

-- 
Best regards
Tianyu Lan

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