From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752334AbdI2Qjo (ORCPT ); Fri, 29 Sep 2017 12:39:44 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:38635 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752203AbdI2Qjn (ORCPT ); Fri, 29 Sep 2017 12:39:43 -0400 X-Google-Smtp-Source: AOwi7QCYPR3wAevtAB1EExq4DWf8Bt/rySL52YNX6Iu8zbLqq40GqT7Ponbmbe3sZkIeVe8TDGqD2w== Subject: Re: KVM PV (was: Re: [PATCH v2 2/2] x86/lguest: remove lguest support) To: Lai Jiangshan , LKML , kvm@vger.kernel.org Cc: xen-devel@lists.xenproject.org, x86@kernel.org, lguest@lists.ozlabs.org, Boris Ostrovsky , "H. Peter Anvin" , Thomas Gleixner , mingo@redhat.com, rusty@rustcorp.com.au, Juergen Gross References: From: Paolo Bonzini Message-ID: <4102561f-b403-735e-a18a-7c55db57df74@redhat.com> Date: Fri, 29 Sep 2017 18:39:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 29/09/2017 17:47, Lai Jiangshan wrote: > Hello, all > > An interesting (at least to me) thinking came up to me when I found > that the lguest was removed. But I don't have enough knowledge > to find out the answer nor energy to implement it in some time. > > Is it possible to implement kvm-pv which allows kvm to run on > the boxes without hardware virtualization support, so that > qemu/kvm can be used on clouds such as aws, azure? No, please don't. :) Even Xen is moving from PV to PVH (paravirtualized hardware with event channels, grant tables and the like, but still using hardware extensions for MMU). Rather, cloud providers should help getting nested virtualization ready for production use. At least for KVM it's not that far. Paolo > Without hardware virtualization support, the host kvm-pv module and > the guest linux kernel need to cooperate in some ways. And some kvm > facilities can help. For instance, the existing shadow-paging, which > was not introduced when lguest had been added to kernel, could be > reused to help on mmu virtualization. For guest kernel/userspace > separation in x86_64, the intel cpu's segment registers can help too. > (or use a new set of page-table for the guest kernel on amd64). > > The thought is quite shallow, but I hope this email brings some > inspirations rather than annoyance. And I'm sorry if the later things > would happen. > > Thanks, > Lai. > > On Thu, Aug 17, 2017 at 1:31 AM, Juergen Gross wrote: >> Lguest seems to be rather unused these days. It has seen only patches >> ensuring it still builds the last two years and its official state is >> "Odd Fixes". >> >> Nuke it in order to be able to clean up the paravirt code. >