From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH V5 10/10] xen/arm64: increase MAX_VIRT_CPUS to 128 on arm64 Date: Sun, 31 May 2015 19:21:22 +0100 Message-ID: <556B5122.2050101@citrix.com> References: <1432984051-10838-1-git-send-email-cbz@baozis.org> <1432984051-10838-11-git-send-email-cbz@baozis.org> <556B0F6B.1060000@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta3.messagelabs.com ([195.245.230.39]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1Yz7rS-0005PP-Rm for xen-devel@lists.xenproject.org; Sun, 31 May 2015 18:21:26 +0000 In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Chen Baozi , Julien Grall Cc: xen-devel@lists.xenproject.org, Chen Baozi , Campbell Ian List-Id: xen-devel@lists.xenproject.org Hi Chen, On 31/05/2015 16:37, Chen Baozi wrote: > >> On May 31, 2015, at 21:40, Julien Grall wrote: >> >> Hi Chen, >> >> On 30/05/2015 12:07, Chen Baozi wrote: >>> From: Chen Baozi >>> >>> GIC-500 supports up to 128 cores in a single SoC. Increase MAX_VIRT_CPUS >>> to 128 on arm64. >> >> Where did you find this restriction? AFAICT the changes you made in the vGICv3 driver allow us to use up to 4096 CPUs. > > In ARM DDI0516B (ARM CoreLinkTM GIC-500 Generic Interrupt Controller > Technical Reference Manual): > > 1.1 About the GIC-500 > > The GIC-500 is a build-time configurable interrupt controller that supports up to 128 cores. > ... > > And GIC-500 is the only GICv3 implementation as far as I know. The only implementation hardware ;). The vGICv3 in both KVM and Xen are 2 other implementations but software. For instance, with your series a cluster can use up to 16 cores but the GIC-500 is only supporting up to 8 cores... Regards, -- Julien Grall