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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 05897C3DA7F for ; Fri, 26 Jul 2024 12:53:03 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sXKRF-0007bk-H0; Fri, 26 Jul 2024 08:52:50 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sXKR1-0007MS-BY for qemu-devel@nongnu.org; Fri, 26 Jul 2024 08:52:37 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1sXKQx-0002sv-Dl for qemu-devel@nongnu.org; Fri, 26 Jul 2024 08:52:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721998349; 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=yezTynRGclrUQSM6OY+EIuWUKqt9v7YX+5YM6Gwd5wc=; b=Y80U90/KV7Emc6aNkZVrIMn4Zo2dZy+3PZPZSJAF3rfj2zQXyfWhPt8sp3kT9jVUs1sXp5 NNCP1d2P9EuIX5KDvRYbajTehofCZbx84doWVu+l95y+5pja99wkKMOSq87v8MFQCnp4MC dbU2FJoUOa+sPJPx7ma2scC5uNe/dJ0= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-620-IvNDODDNNg6wSeUbPkayzQ-1; Fri, 26 Jul 2024 08:52:25 -0400 X-MC-Unique: IvNDODDNNg6wSeUbPkayzQ-1 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-427df7c3a2aso15020035e9.1 for ; Fri, 26 Jul 2024 05:52:24 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1721998344; x=1722603144; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yezTynRGclrUQSM6OY+EIuWUKqt9v7YX+5YM6Gwd5wc=; b=lRlqz+l145FrJxOUJjXNHlnL3jwxi3OPUywqMEDivu2I3QTgeBV5YqGxm1dAzjrtdI i5dbH730RJt43pFxJ5VZnp316aRTFm/0zCkhUHDQPmfhSre5UnIWrezEE6hA96Px+au7 KB2wgvhs26i8zGwPqR67kMF552LgtaG7jqhYfrPYlZTaMx1h6rmio2lNhsuATzC1RjW/ uZJ5P2qGgP306I9vfrLxtX+1GtWv0d3d55OQJYtVec/mqwp/Y1+Wb8tApL2zOBIpApgN 49nNxiOh45WHJdWuR3ZNC0ltCDoSMqqZ5pulM0y2VgLxbZdrChThTNPAc3rGmOOEZGZh 9PgQ== X-Forwarded-Encrypted: i=1; AJvYcCUdwD466FrZ4F+Nv4fESRkVQHpvst4JDtPo4asQFef8hhv2HT5kcDr7VksJMNzAc7T3uwG2h2IYMOrko+czFtzN+in3sdc= X-Gm-Message-State: AOJu0YyMoiUSW0ktq6o0Y1V05TPY1J2Sb2m3jfcMdnHcAEXRdrnXo5WO Q8TMH6M0EV7NtItfVfY4KgAXNpljxlXqJWqwWosZuTNHVZVj619+PvlmLzH1/QTlYoWB2T2Pt9Q tKoAFQAm1CzYNLj1NlbLB5PqrbrUygjtW7FGw1az+7CkRrG7L60TK X-Received: by 2002:a7b:cc13:0:b0:426:6876:83bb with SMTP id 5b1f17b1804b1-42806b94444mr35917385e9.17.1721998343798; Fri, 26 Jul 2024 05:52:23 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEeZtYe8A1GZTEmL+i7voXFimPt8dBDRrCiuydzX4tPFYqbNapaldNesLi/P0+Gt5ylw7JbVQ== X-Received: by 2002:a7b:cc13:0:b0:426:6876:83bb with SMTP id 5b1f17b1804b1-42806b94444mr35916735e9.17.1721998341579; Fri, 26 Jul 2024 05:52:21 -0700 (PDT) Received: from redhat.com ([2a02:14f:1f7:28ce:f21a:7e1e:6a9:f708]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36b36863b45sm5219141f8f.107.2024.07.26.05.52.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jul 2024 05:52:20 -0700 (PDT) Date: Fri, 26 Jul 2024 08:52:16 -0400 From: "Michael S. Tsirkin" To: David Woodhouse Cc: Richard Cochran , Peter Hilber , linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org, "Ridoux, Julien" , virtio-dev@lists.linux.dev, "Luu, Ryan" , "Chashper, David" , "Mohamed Abuelfotoh, Hazem" , "Christopher S . Hall" , Jason Wang , John Stultz , netdev@vger.kernel.org, Stephen Boyd , Thomas Gleixner , Xuan Zhuo , Marc Zyngier , Mark Rutland , Daniel Lezcano , Alessandro Zummo , Alexandre Belloni , qemu-devel , Simon Horman Subject: Re: [PATCH] ptp: Add vDSO-style vmclock support Message-ID: <20240726084836-mutt-send-email-mst@kernel.org> References: <20240725122603-mutt-send-email-mst@kernel.org> <0959390cad71b451dc19e5f9396d3f4fdb8fd46f.camel@infradead.org> <20240725163843-mutt-send-email-mst@kernel.org> <20240725170328-mutt-send-email-mst@kernel.org> <20240725174327-mutt-send-email-mst@kernel.org> <9261e393083bcd151a017a5af3345a1364b3e0f3.camel@infradead.org> <20240726015613-mutt-send-email-mst@kernel.org> <2e427b102d8fd899a9a3db2ec17a628beb24bc01.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e427b102d8fd899a9a3db2ec17a628beb24bc01.camel@infradead.org> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.143, 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_H4=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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Jul 26, 2024 at 09:35:51AM +0100, David Woodhouse wrote: > But for this use case, we only need a memory region that the hypervisor > can update. We don't need any of that complexity of gratuitously > interrupting all the vCPUs just to ensure that none of them can be > running userspace while one of them does an update for itself, > potentially translating from one ABI to another. The hypervisor can > just update the user-visible memory in place. Looks like then your userspace is hypervisor specific, and that's a problem because it's a one way street - there is no way for hypervisor to know what does userspace need, so no way for hypervisor to know which information to provide. No real way to fix bugs. -- MST