From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199]) (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 E8D646FE25; Thu, 14 Mar 2024 14:20:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.92.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710426005; cv=none; b=P5VJIsMh7CT8qeYi1K4msLLFxUHOVmKFisirj0qBdgSiygUXaldVNB65d+k2En4g/D7VbXuriAbynpmTJpy+DtTGtXSp5cMsXjM+eGq7FhIF3yLq5kNv4NQMuBCByy8rJ/sDcRGzWCADNAZQfFoVxwPx02rHSpDmTg0eX1mzeUw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710426005; c=relaxed/simple; bh=4H7LF9xic1h2s2SK9pUmAgHDyT+hWOLMRCNt/9GcopY=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=OSzFzajXpESF+4xTt6nfLcuTvNZM98q5TGJ4DpT+cJ6uy75605MuY39vq6BXIIF/yAu7oEZ4a4OhxugzjJ4kg6ORAcOBAU0arO4G/37NZ56Qpwk7RtCIRJTCDmZZPcGjGf7VomMVKotvjSnpRusFH3OnpYsEROVhZ39qTgElXlw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=desiato.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=dLRdWswQ; arc=none smtp.client-ip=90.155.92.199 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=desiato.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="dLRdWswQ" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=Content-Transfer-Encoding:Content-Type :MIME-Version:Message-ID:References:In-Reply-To:Subject:CC:To:From:Date: Sender:Reply-To:Content-ID:Content-Description; bh=4H7LF9xic1h2s2SK9pUmAgHDyT+hWOLMRCNt/9GcopY=; b=dLRdWswQiOdn/5ZfCwgv+BcmnZ MavcWDrKg+fI81HsMu1+QsmlnIPBKDANlNkB1KR5EtJ7BO4z1u7IGaG0yIysccG2EtBhhZFhThz3F IjOB5V9ptVMAEh/B2txmxf7iJMxnurWe5ZcTpmRCm5PxOB+KGvLb6+KAYa3FPrnSjsUPHj5OEFpf9 7p36zwfWH/TwxECdok37fgJcWCNOjENsB7Jh67Vh7cG27X6nZ0qiJI4IlBiOB18pSh81SmGqedsVV Ee6cSi8b46TNWHIWEahZFqqzWgpZxovQjtef2HiEJHR9WXDFHhGxCGFgdWopQey/+57vXQy7TZ+ss gfMsib9g==; Received: from [31.94.26.231] (helo=[127.0.0.1]) by desiato.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1rklw3-0000000AW6m-201T; Thu, 14 Mar 2024 14:19:56 +0000 Date: Thu, 14 Mar 2024 15:19:53 +0100 From: David Woodhouse To: Peter Hilber , linux-kernel@vger.kernel.org, virtualization@lists.linux.dev, virtio-dev@lists.oasis-open.org, linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org, "virtio-comment@lists.oasis-open.org" CC: "Christopher S. Hall" , Jason Wang , John Stultz , "Michael S. Tsirkin" , netdev@vger.kernel.org, Richard Cochran , Stephen Boyd , Thomas Gleixner , Xuan Zhuo , Marc Zyngier , Mark Rutland , Daniel Lezcano , Alessandro Zummo , Alexandre Belloni , "Ridoux, Julien" , Cornelia Huck Subject: Re: [RFC PATCH v3 0/7] Add virtio_rtc module and related changes User-Agent: K-9 Mail for Android In-Reply-To: <2eb5a616-eeb3-446a-85fd-fff376c15f55@opensynergy.com> References: <20231218073849.35294-1-peter.hilber@opensynergy.com> <0e21e3e2be26acd70b5575b9932b3a911c9fe721.camel@infradead.org> <204c6339-e80d-4a98-8d07-a11eeb729497@opensynergy.com> <667c8d944ce9ea5c570b82b1858a70cc67b2f3e4.camel@infradead.org> <57704b2658e643fce30468dffd8c1477607f59fb.camel@infradead.org> <47bf0757de3268c420d2cd3bbffaf5897b67b661.camel@infradead.org> <60607bcc-93c5-4a6f-832d-ea4dbd81178e@opensynergy.com> <89268C36-E8FB-4A17-8F81-1DED4BF47400@infradead.org> <2eb5a616-eeb3-446a-85fd-fff376c15f55@opensynergy.com> Message-ID: <9455F710-E38C-45DA-9883-EC034495ADEF@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-SRS-Rewrite: SMTP reverse-path rewritten from by desiato.infradead.org. See http://www.infradead.org/rpr.html On 14 March 2024 11:13:37 CET, Peter Hilber wrote: >> To a certain extent, as long as the virtio-rtc device is designed to ex= pose time precisely and unambiguously, it's less important if the Linux ker= nel *today* can use that=2E Although of course we should strive for that=2E= Let's be=2E=2E=2Ewell, *unambiguous*, I suppose=2E=2E=2E that we've change= d topics to discuss that though=2E >>=20 > >As Virtio is extensible (unlike hardware), my approach is to mostly speci= fy >only what also has a PoC user and a use case=2E If we get memory-mapped (X, Y, Z, =C2=B1x, =C2=B1y) I'll have a user and a= use case on day one=2E Otherwise, as I said in my first response, I can go= do that as a separate device and decide that virtio_rtc doesn't meet our n= eeds (especially for maintaining accuracy over LM)=2E My main concern for virto_rtc is that we avoid *ambiguity*=2E Yes, I get t= hat it's extensible but we don't want a v1=2E0 of the spec, implemented by = various hypervisors, which still leaves guests not knowing what the actual = time is=2E That would not be good=2E And even UTC without a leap second ind= icator has that problem=2E