From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: [PATCH RFC 0/1] Introduce VCPUOP_reset_vcpu_info Date: Wed, 6 Aug 2014 11:03:07 -0400 Message-ID: <20140806150307.GC14744@laptop.dumpdata.com> References: <1407330502-18768-1-git-send-email-vkuznets@redhat.com> <53E253470200007800029C1D@mail.emea.novell.com> <20140806144912.GE13079@laptop.dumpdata.com> <53E25DE10200007800029C9C@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XF2kH-0005Yw-BG for xen-devel@lists.xenproject.org; Wed, 06 Aug 2014 15:03:17 +0000 Content-Disposition: inline In-Reply-To: <53E25DE10200007800029C9C@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel@lists.xenproject.org, Andrew Jones , Vitaly Kuznetsov , David Vrabel , Stefano Stabellini List-Id: xen-devel@lists.xenproject.org On Wed, Aug 06, 2014 at 03:54:57PM +0100, Jan Beulich wrote: > >>> On 06.08.14 at 16:49, wrote: > > On Wed, Aug 06, 2014 at 03:09:43PM +0100, Jan Beulich wrote: > >> Just for my understanding of why exactly you need the new operation: > >> Why is this being done here, when you already do the reset in the > >> cpu-die/shutdown paths? And why not for CPU 0? > >> > >> Furthermore, what is the state of vCPU-s beyond 31 going to be after > >> they got their vCPU info reset? They won't have any other area as > >> fallback. Yet I don't think you can now and forever guarantee that > >> native_cpu_die() won't do anything requiring that structure. > > > > native_cpu_die just spins around in an infinite halt sequence. The > > call could be replaced with the VCPU_down call instead, something like: > > > > if (xen_teardown_cpu(cpu) == -ENOSYS) > > native_cpu_die(); > > > > (void)HYPERVISOR_vcpu_op(VCPUP_down, cpu, NULL); > > But the suggested new hypercall requires the vCPU to be down in > order to allow the reset... Duh! I wrote it and I should have remember that :-) It is RFC for a reason! > > Jan >