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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,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 E84C7C433E0 for ; Tue, 5 Jan 2021 19:45:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8157022D5A for ; Tue, 5 Jan 2021 19:45:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8157022D5A 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 DE0D88D00AB; Tue, 5 Jan 2021 14:45:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D6AA98D006E; Tue, 5 Jan 2021 14:45:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C59748D00AB; Tue, 5 Jan 2021 14:45:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0235.hostedemail.com [216.40.44.235]) by kanga.kvack.org (Postfix) with ESMTP id B0F928D006E for ; Tue, 5 Jan 2021 14:45:58 -0500 (EST) Received: from smtpin24.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 7A447824556B for ; Tue, 5 Jan 2021 19:45:58 +0000 (UTC) X-FDA: 77672751996.24.snake94_110c6d9274db Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin24.hostedemail.com (Postfix) with ESMTP id 5C3F71A4A7 for ; Tue, 5 Jan 2021 19:45:58 +0000 (UTC) X-HE-Tag: snake94_110c6d9274db X-Filterd-Recvd-Size: 4551 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [63.128.21.124]) by imf42.hostedemail.com (Postfix) with ESMTP for ; Tue, 5 Jan 2021 19:45:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1609875957; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MDQ3f1Bz+DgAubnbVzGBFyj256LtO1Sf/sJvuZ9kXFY=; b=aTpmULomtJwGFllyI4EKtN9piqLRb1qfqAskJ189t1FmV2e9NIw6swqKGFLOTSI3mVcq5y pVKFRI8ts/m78Clj6tRhxUNFWTe6DUV8N/im7IRP2Eyvy1Xao0nSia0JgqHk+43mI7iYZ9 aACBJdh9jU3qVr8hcJTaNFCHzdnLGVU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-590-3jSJ7scBN7G90PU-NrNdHA-1; Tue, 05 Jan 2021 14:45:53 -0500 X-MC-Unique: 3jSJ7scBN7G90PU-NrNdHA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D4203800D55; Tue, 5 Jan 2021 19:45:51 +0000 (UTC) Received: from mail (ovpn-112-76.rdu2.redhat.com [10.10.112.76]) by smtp.corp.redhat.com (Postfix) with ESMTPS id EF2145D6CF; Tue, 5 Jan 2021 19:45:47 +0000 (UTC) Date: Tue, 5 Jan 2021 14:45:47 -0500 From: Andrea Arcangeli To: Nadav Amit Cc: Peter Xu , Peter Zijlstra , linux-mm , lkml , Yu Zhao , Andy Lutomirski , Pavel Emelyanov , Mike Kravetz , Mike Rapoport , Minchan Kim , Will Deacon , Mel Gorman Subject: Re: [RFC PATCH v2 1/2] mm/userfaultfd: fix memory corruption due to writeprotect Message-ID: References: <20201225092529.3228466-2-namit@vmware.com> <20210104122227.GL3021@hirez.programming.kicks-ass.net> <73EE9007-65AF-4416-9930-D992C74447A9@vmware.com> <2844ACC1-8908-494C-B411-3C69B27A1730@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/2.0.4 (2020-12-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 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 Tue, Jan 05, 2021 at 07:05:22PM +0000, Nadav Amit wrote: > > On Jan 5, 2021, at 10:45 AM, Andrea Arcangeli w= rote: > > I just don't like to slow down a feature required in the future for > > implementing postcopy live snapshotting or other snapshots to userlan= d > > processes (for the non-KVM case, also unprivileged by default if usin= g > > bounce buffers to feed the syscalls) that can be used by open source > > hypervisors to beat proprietary hypervisors like vmware. >=20 > Ouch, that=E2=80=99s uncalled for. I am sure that you understand that I= have no > hidden agenda and we all have the same goal. Ehm I never said you had an hidden agenda, so I'm not exactly why you're accusing me of something I never said. I merely pointed out one relevant justification for increasing kernel complexity here by not slowing down clear_refs longstanding O(N) clear_refs/softdirty feature and the recent uffd-wp O(1) feature, is to be more competitive with proprietary software solutions, since at least for uffd-wp, postcopy live snapshotting that the #1 use case. I never questioned your contribution or your preference, to be even more explicit, it never crossed my mind that you have an hidden agenda. However since everyone already acked your patches and I'm not ok with your patches because they will give a hit to KVM postcopy live snapshotting and other container clear_refs users, I have to justify why I NAK your patches and remaining competitive with proprietary hypervisors is one of them, so I don't see what is wrong to state a tangible end goal here. Thanks, Andrea