From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,SUBJ_ALL_CAPS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 590CEC352AA for ; Wed, 2 Oct 2019 17:06:01 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 297A42086A for ; Wed, 2 Oct 2019 17:06:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 297A42086A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id AC2E06B0005; Wed, 2 Oct 2019 13:06:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A4C136B0006; Wed, 2 Oct 2019 13:06:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 913626B0007; Wed, 2 Oct 2019 13:06:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0198.hostedemail.com [216.40.44.198]) by kanga.kvack.org (Postfix) with ESMTP id 69C176B0005 for ; Wed, 2 Oct 2019 13:06:00 -0400 (EDT) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with SMTP id F419862EB for ; Wed, 2 Oct 2019 17:05:59 +0000 (UTC) X-FDA: 75999472080.07.year35_8b8d1590e2048 X-HE-Tag: year35_8b8d1590e2048 X-Filterd-Recvd-Size: 4375 Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by imf38.hostedemail.com (Postfix) with ESMTP for ; Wed, 2 Oct 2019 17:05:58 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 385CB87648; Wed, 2 Oct 2019 17:05:57 +0000 (UTC) Received: from redhat.com (ovpn-112-77.rdu2.redhat.com [10.10.112.77]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7408F5C3F8; Wed, 2 Oct 2019 17:05:46 +0000 (UTC) Date: Wed, 2 Oct 2019 13:04:29 -0400 From: Jerome Glisse To: Paolo Bonzini Cc: Mircea CIRJALIU - MELIU , Adalbert =?utf-8?B?TGF6xINy?= , Matthew Wilcox , "kvm@vger.kernel.org" , "linux-mm@kvack.org" , "virtualization@lists.linux-foundation.org" , Radim =?utf-8?B?S3LEjW3DocWZ?= , Konrad Rzeszutek Wilk , Tamas K Lengyel , Mathieu Tarral , Samuel =?iso-8859-1?Q?Laur=E9n?= , Patrick Colp , Jan Kiszka , Stefan Hajnoczi , Weijiang Yang , Yu C , Mihai =?utf-8?B?RG9uyJt1?= Subject: Re: DANGER WILL ROBINSON, DANGER Message-ID: <20191002170429.GA8189@redhat.com> References: <20190815191929.GA9253@redhat.com> <20190815201630.GA25517@redhat.com> <20190905180955.GA3251@redhat.com> <5b0966de-b690-fb7b-5a72-bc7906459168@redhat.com> <20191002192714.GA5020@redhat.com> <20191002141542.GA5669@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Wed, 02 Oct 2019 17:05:57 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Oct 02, 2019 at 06:18:06PM +0200, Paolo Bonzini wrote: > On 02/10/19 16:15, Jerome Glisse wrote: > >>> Why would you need to target mmu notifier on target vma ? > >> If the mapping of the source VMA changes, mirroring can update the > >> target VMA via insert_pfn. But what ensures that KVM's MMU notifier > >> dismantles its own existing page tables (so that they can be recreat= ed > >> with the new mapping from the source VMA)? > >> > > So just to make sure i follow we have: > > - qemu process on host with anonymous vma > > -> host cpu page table > > - kvm which maps host anonymous vma to guest > > -> kvm guest page table > > - kvm inspector process which mirror vma from qemu process > > -> inspector process page table > >=20 > > AFAIK the KVM notifier's will clear the kvm guest page table whenever > > necessary (through kvm_mmu_notifier_invalidate_range_start). This is > > what ensure that KVM's dismatles its own mapping, it abides to mmu- > > notifier callbacks. If you did not you would have bugs (at least i > > expect so). Am i wrong here ? >=20 > The KVM inspector process is also (or can be) a QEMU that will have to > create its own KVM guest page table. Ok missed that part, thank you for explaining >=20 > So if a page in the source VMA is unmapped we want: >=20 > - the source KVM to invalidate its guest page table (done by the KVM MM= U > notifier) >=20 > - the target VMA to be invalidated (easy using mirroring) >=20 > - the target KVM to invalidate its guest page table, as a result of > invalidation of the target VMA You can do the target KVM invalidation inside the mirroring invalidation code. Cheers, J=E9r=F4me