From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chegu Vinod <chegu_vinod@hp.com>
Subject: Re: KVM_MAX_VCPUS
Date: Sun, 14 Oct 2012 06:42:58 -0700
Message-ID: <507AC162.9040609@hp.com>
References: <5079EB5B.8080102@hp.com> <507A242D.9070708@gmail.com> <20121014090825.GM16648@redhat.com>
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Cc: Sasha Levin <levinsasha928@gmail.com>, KVM <kvm@vger.kernel.org>
To: Gleb Natapov <gleb@redhat.com>
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On 10/14/2012 2:08 AM, Gleb Natapov wrote:
> On Sat, Oct 13, 2012 at 10:32:13PM -0400, Sasha Levin wrote:
>> On 10/13/2012 06:29 PM, Chegu Vinod wrote:
>>> Hello,
>>>
>>> Wanted to get a clarification about KVM_MAX_VCPUS(currently set to 254)
>>>   in kvm_host.h file. The kvm_vcpu *vcpus array is sized based on KVM_MAX_VCPUS.
>>> (i.e. a max of 254 elements in the array).
>>>   
>>> An 8bit APIC id should allow for 256 ID's. Reserving one for Broadcast should
>>> leave 255 ID's.  Is there one more ID reserved for some other purpose ? (hence
>>> leading to KVM_MAX_VCPUS being set to 254 and not 255).
>> Another ID goes to the IO-APIC.
>>
> This is not really needed on KVM. We can enlarge KVM_MAX_VCPUS to 255.

Thanks for clarification!  ( We did suspect the IO-APIC...but weren't 
quite sure).

Vinod
>
> --
> 			Gleb.
> .
>