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[128.59.11.253]) by mx.google.com with ESMTP id k85-v6si11358795qkh.357.2018.07.24.23.45.10; Tue, 24 Jul 2018 23:45:11 -0700 (PDT) Received-SPF: pass (google.com: domain of kvmarm-bounces@lists.cs.columbia.edu designates 128.59.11.253 as permitted sender) client-ip=128.59.11.253; Authentication-Results: mx.google.com; spf=pass (google.com: domain of kvmarm-bounces@lists.cs.columbia.edu designates 128.59.11.253 as permitted sender) smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 6D4A44A129; Wed, 25 Jul 2018 02:45:10 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu X-Spam-Flag: NO X-Spam-Score: -1.502 X-Spam-Level: X-Spam-Status: No, score=-1.502 required=6.1 tests=[BAYES_00=-1.9, DNS_FROM_AHBL_RHSBL=2.699, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_PASS=-0.001] autolearn=no 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 kWHucHfJmgsQ; Wed, 25 Jul 2018 02:45:09 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 4668F4A102; Wed, 25 Jul 2018 02:45:09 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 67305404D9 for ; Wed, 25 Jul 2018 02:45:07 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu 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 5q+wGqFGTwJj for ; Wed, 25 Jul 2018 02:45:06 -0400 (EDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 1C74540493 for ; Wed, 25 Jul 2018 02:45:06 -0400 (EDT) Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8FEEC401EF0C; Wed, 25 Jul 2018 06:45:05 +0000 (UTC) Received: from localhost (ovpn-204-26.brq.redhat.com [10.40.204.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id DFB892026D68; Wed, 25 Jul 2018 06:45:02 +0000 (UTC) Date: Wed, 25 Jul 2018 08:45:02 +0200 From: Igor Mammedov To: Maran Wilson Subject: Re: [Qemu-devel] VCPU hotplug on KVM/ARM Message-ID: <20180725084502.751106ed@redhat.com> In-Reply-To: References: <000e01d3afad$b9a13830$2ce3a890$@codeaurora.org> <20180227104708.GA11391@cbox> <20180227124604.GA2373@cbox> <20180227132131.fipafmnb56a7fj76@kamzik.brq.redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 25 Jul 2018 06:45:05 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.5]); Wed, 25 Jul 2018 06:45:05 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'imammedo@redhat.com' RCPT:'' Cc: Christoffer Dall , Christoffer Dall , marc.zyngier@arm.com, david@redhat.com, qemu-devel@nongnu.org, Christoffer Dall , qemu-arm@nongnu.org, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu X-TUID: e+UROUqVWpeI On Tue, 24 Jul 2018 11:35:31 -0700 Maran Wilson wrote: > It's been a few months since this email thread died off. Has anyone > started working on a potential solution that would allow VCPU hotplug on > KVM/ARM ? Or is this a project that is still waiting for an owner who > has the time and inclination to get started? I'm working on QEMU side of it as time allows. I can guide or share task if are you interested in helping out with it? > Thanks, > -Maran > > On 2/27/2018 5:21 AM, Andrew Jones wrote: > > On Tue, Feb 27, 2018 at 01:46:04PM +0100, Christoffer Dall wrote: > >> On Tue, Feb 27, 2018 at 05:34:28PM +0530, bthakur@codeaurora.org wrote: > >>> Hi Christoffer, > >>> > >>> Thanks for your reply. > >>> > >>> On 2018-02-27 16:17, Christoffer Dall wrote: > >>>> Hi Bhupinder, > >>>> > >>>> On Tue, Feb 27, 2018 at 03:01:17PM +0530, bthakur@codeaurora.org wrote: > >>>>> I hope it is the right forum to post my query. > >>>>> > >>>>> > >>>>> > >>>>> I am currently looking at the possibility of adding a new VCPU to a > >>>>> running > >>>>> guest VM in KVM/ARM. I see that currently, it is not allowed to add a > >>>>> new > >>>>> VCPU to a guest VM, if it is already initialized. The first check in > >>>>> kvm_arch_vcpu_create() returns failure if it is already initialized. > >>>>> > >>>> This would require a major rework of a lot of logic surrounding the GIC > >>>> and other parts of KVM initialization. > >>>> > >>>>> > >>>>> There was some work done in QEMU to add support for VCPU hotplug: > >>>>> https://lists.gnu.org/archive/html/qemu-arm/2017-05/msg00404.html > >>>>> > >>>>> > >>>>> > >>>>> But I am looking at the KVM side for enabling adding a new VCPU. If you > >>>>> can > >>>>> point me to any relevant work/resources, which I can refer to then it > >>>>> will > >>>>> help me. > >>>>> > >>>> I don't have any specific pointers, but I was always told that the way > >>>> we were going to do CPU hotplug would be to instantiate a large number > >>>> of VCPUs, and hotplug would be equivalent to turning on a VCPU which was > >>>> previously powered off. > >>>> > >>>> Is this not still a feasible solution? > >>> It should be a feasible solution provided the guest VM is not able to > >>> control the onlining/offlining of VCPUs. It should be controlled by the > >>> Host. > >>> > >> KVM could simply refuse to turn on some of the CPUs unless given > >> permission from host userspace. > >> > >>>> How does VCPU hotplug work on x86? > >>> On x86, you can add a vcpu through libvirt setvcpu command and it shows up > >>> in the guest VM as a new CPU if you do lscpu. > >>> > >> Sure, but what is the mechanism, does x86 qemu actually call > >> KVM_CREATE_VCPU, or is this also a question of turning on already > >> created vcpus ? > >> > > CC'ing Igor and qemu-devel > > > > drew > > _______________________________________________ > > kvmarm mailing list > > kvmarm@lists.cs.columbia.edu > > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm > > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm