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 8C179C3DA49 for ; Thu, 25 Jul 2024 11:32:49 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sWwhe-0002A5-S9; Thu, 25 Jul 2024 07:32:10 -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 1sWwhd-00027x-Cu for qemu-devel@nongnu.org; Thu, 25 Jul 2024 07:32:09 -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 1sWwhZ-0006fu-Dn for qemu-devel@nongnu.org; Thu, 25 Jul 2024 07:32:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721907123; h=from:from:reply-to: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=vyKLgMRT6i9mXd45Il7wt/ZZwWvsdwnv5UBxyQ1yU1Y=; b=TmX+zDRZWjCHcjXm67priOGGuK0naa2+XvCEqXGV3UQkn+fxObRSf2b0Ypf5EblgqUcXVH dDhujOK/JbPWNNogoStIn7IQbknbx/F5uND0GjUKsE8wgjVJkMGY+/VzbZKB7TLesomDXD qZIWK5dLhaqHTDsqkgBVW/zDdPiHiqw= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-226-Rp-aJfBJPT209rAmpqTPUg-1; Thu, 25 Jul 2024 07:31:58 -0400 X-MC-Unique: Rp-aJfBJPT209rAmpqTPUg-1 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8B4C31955D50; Thu, 25 Jul 2024 11:31:54 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.144]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C6C453000197; Thu, 25 Jul 2024 11:31:45 +0000 (UTC) Date: Thu, 25 Jul 2024 12:31:42 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: David Woodhouse Cc: "Michael S. Tsirkin" , 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: References: <14d1626bc9ddae9d8ad19d3c508538d10f5a8e44.camel@infradead.org> <20240725012730-mutt-send-email-mst@kernel.org> <7de7da1122e61f8c64bbaab04a35af93fafac454.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <7de7da1122e61f8c64bbaab04a35af93fafac454.camel@infradead.org> User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@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=-0.144, 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Thu, Jul 25, 2024 at 10:56:05AM +0100, David Woodhouse wrote: > Hi Michael, thanks for the review! > > On Thu, 2024-07-25 at 01:48 -0400, Michael S. Tsirkin wrote: > > On Wed, Jul 24, 2024 at 06:16:37PM +0100, David Woodhouse wrote: > > > From: David Woodhouse > > > > > > The vmclock "device" provides a shared memory region with precision clock > > > information. By using shared memory, it is safe across Live Migration. > > > > > > Like the KVM PTP clock, this can convert TSC-based cross timestamps into > > > KVM clock values. Unlike the KVM PTP clock, it does so only when such is > > > actually helpful. > > > > > > The memory region of the device is also exposed to userspace so it can be > > > read or memory mapped by application which need reliable notification of > > > clock disruptions. > > > > > > Signed-off-by: David Woodhouse > > > --- > > > QEMU implementation at > > > https://git.infradead.org/users/dwmw2/qemu.git/shortlog/refs/heads/vmclock > > > > > > Although the ACPI device implemented in QEMU (and some other > > > hypervisor) stands alone, most of the fields and values herein are > > > aligned as much as possible with the nascent virtio-rtc specification, > > > with the intent that a version of the same structure can be > > > incorporated into that standard. > > > > Do you want to just help complete virtio-rtc then? Would be easier than > > trying to keep two specs in sync. > > The ACPI version is much more lightweight and doesn't take up a > valuable PCI slot#. (I know, you can do virtio without PCI but that's > complex in other ways). In general it shouldn't have to take up a PCI slot, that's just a common default policy. virtio-devices only need a dedicated slot if there's a need to do hotplug/unplug of them. There is a set of core devices for which hotplug doesn't make sense, which could all be put as functions in the same slot. ie virtio-rng, virtio-balloon and virtio-rtc, could all live in one slot. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|