From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH 3/5] arm/arm64: KVM: Clarify KVM_ARM_VCPU_INIT ABI Date: Tue, 2 Dec 2014 20:02:52 +0100 Message-ID: <20141202190252.GK545@cbox> References: <1417113660-23610-1-git-send-email-christoffer.dall@linaro.org> <1417113660-23610-4-git-send-email-christoffer.dall@linaro.org> <20141202144728.GH545@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "kvmarm@lists.cs.columbia.edu" , arm-mail-list , kvm-devel , Ard Biesheuvel , Marc Zyngier , Alex =?iso-8859-1?Q?Benn=E9e?= To: Peter Maydell Return-path: Received: from mail-la0-f51.google.com ([209.85.215.51]:48579 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752442AbaLBTCO (ORCPT ); Tue, 2 Dec 2014 14:02:14 -0500 Received: by mail-la0-f51.google.com with SMTP id ms9so11083569lab.24 for ; Tue, 02 Dec 2014 11:02:12 -0800 (PST) Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Tue, Dec 02, 2014 at 03:39:05PM +0000, Peter Maydell wrote: > On 2 December 2014 at 14:47, Christoffer Dall > wrote: > > On Thu, Nov 27, 2014 at 10:53:50PM +0000, Peter Maydell wrote: > >> On 27 November 2014 at 18:40, Christoffer Dall > >> wrote: > >> > Possible features: > >> > - KVM_ARM_VCPU_POWER_OFF: Starts the CPU in a power-off state. > >> > Depends on KVM_CAP_ARM_PSCI. If not set, the CPU will be powered on > >> > >> Do you have to use the same set of feature flags for second and > >> subsequent VCPU_INIT calls, or can they be different each time? > >> > > That's a good question. Do you have any opinion on the matter? > > QEMU always will, so I'd be happy if we said it has to be the same > set of flags each time. I guess I'd go for "say they have to match"; > we can always relax later if we need to. > > > It seems weird to change the target of a Vcpu from some core to another > > core, but there is not reason why you shouldn't be able to set a vCpU to > > be powered off when run, just because it wasn't earlier on, is > > there? > > We need an API for get/set of PSCI power state for migration > anyhow, so it's not inherently required to be able to flip > this bit on reset. > Actually I think the current migration patches rely on being able to call the init ioctl to turn off a vcpu, but I guess you could use the KVM_SET_MP_STATE for that. Alex, any thoughts? -Christoffer