From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53764) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1etYU4-0001Of-2N for qemu-devel@nongnu.org; Wed, 07 Mar 2018 07:47:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1etYU3-0006hC-Aa for qemu-devel@nongnu.org; Wed, 07 Mar 2018 07:47:52 -0500 References: <000e01d3afad$b9a13830$2ce3a890$@codeaurora.org> <20180227104708.GA11391@cbox> <20180227124604.GA2373@cbox> <20180227132131.fipafmnb56a7fj76@kamzik.brq.redhat.com> <20180301105030.2b716e68@redhat.com> From: Marc Zyngier Message-ID: Date: Wed, 7 Mar 2018 12:47:39 +0000 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Qemu-arm] VCPU hotplug on KVM/ARM List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Hildenbrand , Peter Maydell , Igor Mammedov Cc: Christoffer Dall , QEMU Developers , Christoffer Dall , qemu-arm , kvmarm@lists.cs.columbia.edu On 01/03/18 13:32, David Hildenbrand wrote: > On 01.03.2018 11:05, Peter Maydell wrote: >> On 1 March 2018 at 09:50, Igor Mammedov wrote: >>> In QEMU on x86 (and I think ppc, s390 as well), we create vCPUs on demand.>> >>> It would be nice if ARM would be able to do that too, >>> so that it could take advantage of the same code. >> >> It's not clear to me how that would work, given that for >> instance the interrupt controller wants to know up-front >> how many CPUs it has to deal with. >> > > So how is cpu hotplug handled in HW? Or doesn't it even exist there? I don't know of any physical system offering that facility. > (we have max_cpus for the interrupt controller, but not sure if that is > what we want) We'd need something along those lines. Each CPU has a notional point to point link to the interrupt controller (to the redistributor, to be precise), and this entity must pre-exist. Thanks, M. -- Jazz is not dead. It just smells funny... From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Zyngier Subject: Re: [Qemu-devel] [Qemu-arm] VCPU hotplug on KVM/ARM Date: Wed, 7 Mar 2018 12:47:39 +0000 Message-ID: References: <000e01d3afad$b9a13830$2ce3a890$@codeaurora.org> <20180227104708.GA11391@cbox> <20180227124604.GA2373@cbox> <20180227132131.fipafmnb56a7fj76@kamzik.brq.redhat.com> <20180301105030.2b716e68@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id E8F0C40259 for ; Wed, 7 Mar 2018 07:40:49 -0500 (EST) Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 98b13yh4wbvQ for ; Wed, 7 Mar 2018 07:40:28 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 8B49D401AB for ; Wed, 7 Mar 2018 07:40:28 -0500 (EST) In-Reply-To: Content-Language: en-GB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu To: David Hildenbrand , Peter Maydell , Igor Mammedov Cc: Christoffer Dall , Christoffer Dall , QEMU Developers , qemu-arm , kvmarm@lists.cs.columbia.edu List-Id: kvmarm@lists.cs.columbia.edu On 01/03/18 13:32, David Hildenbrand wrote: > On 01.03.2018 11:05, Peter Maydell wrote: >> On 1 March 2018 at 09:50, Igor Mammedov wrote: >>> In QEMU on x86 (and I think ppc, s390 as well), we create vCPUs on demand.>> >>> It would be nice if ARM would be able to do that too, >>> so that it could take advantage of the same code. >> >> It's not clear to me how that would work, given that for >> instance the interrupt controller wants to know up-front >> how many CPUs it has to deal with. >> > > So how is cpu hotplug handled in HW? Or doesn't it even exist there? I don't know of any physical system offering that facility. > (we have max_cpus for the interrupt controller, but not sure if that is > what we want) We'd need something along those lines. Each CPU has a notional point to point link to the interrupt controller (to the redistributor, to be precise), and this entity must pre-exist. Thanks, M. -- Jazz is not dead. It just smells funny...