linux-kernel - Re: [PATCH 1/1] kvm: increase max vcpu count

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Message-ID: <20140515101811.GA16070@potion.brq.redhat.com>
Date:	Thu, 15 May 2014 12:18:12 +0200
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	"Li, Zhen-Hua" <zhen-hual@...com>
Cc:	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] kvm: increase max vcpu count

2014-05-15 17:50+0800, Li, Zhen-Hua:
> This patch is trying to increase the maximum supported vcpu number.
> 
> There has been big system supporting more than 256 logical CPUs, and vmware
> can also support guest system with more than logical 256 CPUs. So kvm should 
> also increase the maximum supported cpu number.

How did it work?
KVM lapic does not handle more more than 256 [1] at the moment, so
additional VCPUs had to wraparound ...

---
1: "struct kvm_apic_map" has "struct kvm_lapic *phys_map[256]" and we
   are using "& 0xff" when dealing with it, too.
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