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 18:36, Roger Pau Monné 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.

Yes, that's right and will fix.
-- 
Best regards
Tianyu Lan

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