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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 0E9E0C64E7A for ; Tue, 1 Dec 2020 19:24:14 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 343142168B for ; Tue, 1 Dec 2020 19:24:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="GZjR0SHP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 343142168B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:58918 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kkBFz-0005l3-EU for qemu-devel@archiver.kernel.org; Tue, 01 Dec 2020 14:24:11 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:39730) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kkBEu-0005Hy-3K for qemu-devel@nongnu.org; Tue, 01 Dec 2020 14:23:04 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:27435) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kkBEr-0004NQ-5S for qemu-devel@nongnu.org; Tue, 01 Dec 2020 14:23:03 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1606850580; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=lM8h7rRYrLt35OQZALWfHVM+Gp2wjFmtevJ17Xuxp00=; b=GZjR0SHPGpLEpiHxDn29H2+H5WLXXMf9R8Jj5TubDo940t3ZCkHgWKdzLP4n7lcvJeFX+b yca1GW30+9aJPlPVX+hoY8pHEFU8BpelHd1nW0tjDdadoiE43ifjE3sLOTPO0HE3vo/H/V M81Eo8Maw8EXybD29GHafEcgAS/ZWKY= Received: from mail-qt1-f199.google.com (mail-qt1-f199.google.com [209.85.160.199]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-201--OF2kijHMWuA8jufMppYiA-1; Tue, 01 Dec 2020 14:22:56 -0500 X-MC-Unique: -OF2kijHMWuA8jufMppYiA-1 Received: by mail-qt1-f199.google.com with SMTP id v18so2007822qta.22 for ; Tue, 01 Dec 2020 11:22:56 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=lM8h7rRYrLt35OQZALWfHVM+Gp2wjFmtevJ17Xuxp00=; b=ZRArrNAI6nX20mc8DHfEvJaRg+yewQ9OdqOOQkihodXoq8tTIfOsrbfcjCSqqlgWx8 Gjfnck38NZbLYl7bc0qJ0yzVtgEttjq6G2gNIUhQhcgwfb2odeo6R2man5BLfjsYbX9+ 179zCjQSRsHLYVSzjDyngLEBzqkIh66xB+f+/f1JoP0VMdwiP+l0n/fFdU95Gi7dmExq L4ipZEgM4FqVcccKni1p/4kkKJUjaEmKSPYG2+V+3Y11LikJ2KYdIWHYG0ZIHvbJGYSG dm7SvoPI5OwVm0MVWSw5i72LOWZyCSnx49Dx1sEqyNpx88NMCd+lTca3Fvs/AnIeZIb+ 2Mlg== X-Gm-Message-State: AOAM5328IeSi3mdkUXx1kK3EA0uvpmdfft88OMlLgFpsM9wk1OnOH2k9 g/HqB0w9TT8REitgrjaBHFzV+1DD15VRrjteyLJRfEp+5O9atQk+Js6thZVZymipWpdSAprrSsc 66COl46zbBI75MsI= X-Received: by 2002:a0c:a802:: with SMTP id w2mr4807365qva.9.1606850576142; Tue, 01 Dec 2020 11:22:56 -0800 (PST) X-Google-Smtp-Source: ABdhPJz8EbvzeV1xchvEvE1scyK4QHRZJ+wEwFolrTtT59brs1yQgF4UAWXPUswq9Lkn1MhOlj8tLQ== X-Received: by 2002:a0c:a802:: with SMTP id w2mr4807352qva.9.1606850575906; Tue, 01 Dec 2020 11:22:55 -0800 (PST) Received: from xz-x1 ([142.126.94.187]) by smtp.gmail.com with ESMTPSA id j4sm323988qtq.42.2020.12.01.11.22.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Dec 2020 11:22:55 -0800 (PST) Date: Tue, 1 Dec 2020 14:22:47 -0500 From: Peter Xu To: "Dr. David Alan Gilbert" Subject: Re: [PATCH v4 0/6] UFFD write-tracking migration/snapshots Message-ID: <20201201192247.GF3277@xz-x1> References: <20201126151734.743849-1-andrey.gruzdev@virtuozzo.com> <20201201070820.GO105758@angien.pipo.sk> <20201201105300.GQ105758@angien.pipo.sk> <20201201184055.GM4338@work-vm> MIME-Version: 1.0 In-Reply-To: <20201201184055.GM4338@work-vm> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.497, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Krempa , Juan Quintela , qemu-devel@nongnu.org, Markus Armbruster , Paolo Bonzini , Den Lunev , Andrey Gruzdev Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, Dec 01, 2020 at 06:40:55PM +0000, Dr. David Alan Gilbert wrote: > > Yep, seems that current userfaultfd supports hugetlbfs and shared memory for > > missing pages but not for wr-protected.. > > For hugepages, you'd need kernel support - but also you'd want to make > sure you write the whole hugepage at once. Or we can do similar things by splitting the huge pages just like when we migrate. I should have overlooked these facts when I replied previusly - we do need the same logic, but also special care on these special memory types. > > For shared, there's a harder problem to ask; what happens if RAM is > written by the other process - for postcopy, we get the other process > to send us a userfaultfd that they have registered with their VM. Good point... so we should need similar things too. Looks like we'd better explicitly disable shmem/hugetlbfs for now from qemu background snapshots before we have prepared these utilities, just in case it got run on some "future" kernels and accidentally got enabled, so the snapshot files could be corrupted ones. Is shmem used a lot in libvirt, or is it even a default configuration? -- Peter Xu