From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 970C9198E7E for ; Thu, 25 Jul 2024 11:32:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721907124; cv=none; b=IQRHV2uks/gEdvc2GAztfZEar9ss4yTW0i3SG4q2PpadxsrNbvu5H6klSq4Pq5BoYSlmAAtNKHbBZSrnxQYTz/95srEuULmpcTk/sim/Bt1/Y9FHUByXaCnInkZ0QAuxmjSZ3b2EBY9dkFgro8+L7iJKGcXj5M+sV6N7Ta9AE+o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1721907124; c=relaxed/simple; bh=2PFaAKT/qKzvR5HmQHNT0YtE+EnpJ+3U4z/gAUFLbho=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CDcbRASZG9olNde9Nc8Y/1qis349wpGvdQOrAFzYdreJDVWHkQhxU9W1p6edGPPBjepk24GZoFGsGt8kvyy5lO7jyFrKLJX0nejSuNQ5VeOHeeKY0uoDE4Tequ6TR86DCrqnITNMqbwqoe1Grb39mzIIn/M+SwQurFMT7KSE6VY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=KPvKSvbO; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KPvKSvbO" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1721907121; 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=KPvKSvbOgB8EiJTG6LNh3LEXBiz+GyngOcIiw66TCuvN4HTj+nrWaa88jRR7w0MCHAV8AP YJINPh3RtIEWnSf3r/D+SfOg49qMh7ONa3F1EI+K4zeAGQmUal4ku1epFCFXXPcpQ4Sqvr T7eaPSyj51Y1wvr1yLhAEM7mxrrLUak= 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: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <14d1626bc9ddae9d8ad19d3c508538d10f5a8e44.camel@infradead.org> <20240725012730-mutt-send-email-mst@kernel.org> <7de7da1122e61f8c64bbaab04a35af93fafac454.camel@infradead.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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 :|