From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40220) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ekDWC-0007kT-Rm for qemu-devel@nongnu.org; Fri, 09 Feb 2018 13:35:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ekDW8-00046j-8A for qemu-devel@nongnu.org; Fri, 09 Feb 2018 13:35:28 -0500 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:55420 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ekDW8-00046S-2y for qemu-devel@nongnu.org; Fri, 09 Feb 2018 13:35:24 -0500 Date: Fri, 9 Feb 2018 13:35:06 -0500 From: Luiz Capitulino Message-ID: <20180209133506.3f5dcc1a@redhat.com> In-Reply-To: <48b8aa8e-36f8-1d2c-ee53-d8006cde77bc@linux.vnet.ibm.com> References: <20180208111732.09869f84@redhat.com> <20180208203342.GE13981@localhost.localdomain> <20180209084949.569007d7@redhat.com> <20180209142735.GK13981@localhost.localdomain> <48b8aa8e-36f8-1d2c-ee53-d8006cde77bc@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2] qmp: add query-cpus-fast List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Viktor Mihajlovski Cc: Eduardo Habkost , qemu-devel@nongnu.org, armbru@redhat.com, eblake@redhat.com, berrange@redhat.com On Fri, 9 Feb 2018 15:50:00 +0100 Viktor Mihajlovski wrote: > On 09.02.2018 15:27, Eduardo Habkost wrote: > [...] > >> I'm keeping it mainly for s390. Viktor, libvirt is still using > >> this field in s390, no? > >> > >> Dropping halted and having management software still using query-cpus > >> because of halted would be a total failure of query-cpus-fast. > > > > If I understood correctly, the CpuInfoS390::cpu_state field added > > by Viktor in another patch[1] would replace "halted" for the s390 > > case. > Right, CPUState.halted is derived from CPUS390XState.cpu_state on s390: > A cpu_state of CPU_STATE_STOPPED or CPU_STATE_CHECK_STOPPED results in > halted = true. This derivation can be done by libvirt for s390. > > > > I'm assuming QEMU will be able to return that field without > > interrupting the VCPUs. Viktor, is that correct? > > > > [1] https://lists.gnu.org/archive/html/qemu-devel/2018-02/msg02032.html > > > That's correct. > >> > >>>> Also, the code that sets/clears cpu->halted is target-specific, > >>>> so I wouldn't be so sure that simply checking for > >>>> !kvm_irqchip_in_kernel() is enough on all targets. > >> > >> I checked the code and had the impression it was enough, but > >> I don't have experience with other archs. So, would be nice > >> if other archs maintainers could review this. I'll try to ping them. > > > > I think we need to take a step back and rethink: > > > > 1) What the field is supposed to mean? The semantics of "halted" > > are completely unclear. What exactly we want to communicate > > to libvirt/management? > > 2) On which cases the information (whatever it means) is really > > useful/important? If you are excluding cases with in-kernel > > irqchip, you are already excluding most users. > > > > > Given that nobody (including myself) sees a need for halted we can > remove it for the fast version of query-cpus without surprising anyone. > [...] My conclusion too, I'll drop it.