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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 1C828C30653 for ; Tue, 25 Jun 2024 21:34:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: Message-ID:Date:In-Reply-To:Subject:Cc:To:From:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:References: List-Owner; bh=cBD4zAiF08Tny5sO1Gl2HsuBxAKc5MasJfQRkmugnwI=; b=AnDuLUKao7eL5J rv62ekvbyuGfV3wlKqQ1aOGTSr9FQysrEHvM5pH9hitMQN5HFyhlye9yB3Y/5uIkN9eefevGdvWTH iFvGzz4bUzF1A+JgoeI02IMUmJgMa/1jCBMYvPDECgowPPngQlta/cHVIawaDAvf7ZNdhQNVVSChf 6Q9cB244LWObHleyHAVPzjFPAdtjs5igW1DgidBa59MwvPIux58Hc3eA4I1jVqRRqOwTVfbfbps9c R1PzHtkvvDSHZCMtelUSzXLuNjVcNHLTrabWxCRLcfgO9psEMqaNLxhvrLmOJ7msv1w1cX/yNbMeY s+sXmpJKgBCbFOVABa/A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1sMDoE-00000004ah7-3RZW; Tue, 25 Jun 2024 21:34:38 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1sMDo3-00000004acF-1GK9 for linux-arm-kernel@lists.infradead.org; Tue, 25 Jun 2024 21:34:31 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1719351265; 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; bh=cBD4zAiF08Tny5sO1Gl2HsuBxAKc5MasJfQRkmugnwI=; b=xd7xbvHPrn0WWfzg6B74Sg+5WddYaCIiEgHS+QlK6NmVrMF20WaHrkqdQfEMAYH8W0Lebe jomz94JOpYib8BIKcjNhQgcCBrkX+NSLbumPeu56wdF4zMiNMJ+lXwB9GfP/L3ZVFt923O gDVbv6trHv1Me6PNZWEJvST0AR+biixf/+ieWv0lKZWqvdhSxWCmauQynkfOgfCLuEg8MY bwApIHOJDPq3ZzOZf1v5D/aDLePpYqMAV1v5Fl0SCwxw8D9h1lnO3eIUfE5l+utbW5PKc/ KssfZ8E6EdpbwOiQ9H5qzUCFeD9UW6q7uvCfMGvAM8p6xqZRdVzgPo8LiBTqYw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1719351265; 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; bh=cBD4zAiF08Tny5sO1Gl2HsuBxAKc5MasJfQRkmugnwI=; b=fG2hs6PZ+vtjj+L3x1f4wBjXlrHsTMYW87osvADsyB7iust7q/iXbfYchPW6bVeSfgjt11 Kgiu2FLgNLLz/ADQ== To: David Woodhouse , 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" Cc: "Christopher S. Hall" , Jason Wang , John Stultz , "Michael S. Tsirkin" , netdev@vger.kernel.org, Richard Cochran , Stephen Boyd , Xuan Zhuo , Marc Zyngier , Mark Rutland , Daniel Lezcano , Alessandro Zummo , Alexandre Belloni Subject: Re: [RFC PATCH v2] ptp: Add vDSO-style vmclock support In-Reply-To: <4a0a240dffc21dde4d69179288547b945142259f.camel@infradead.org> Date: Tue, 25 Jun 2024 23:34:24 +0200 Message-ID: <87jzic4sgv.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240625_143427_632811_A647570B X-CRM114-Status: GOOD ( 14.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Jun 25 2024 at 20:01, 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. There is effort underway to expose PTP clocks to user space via VDSO. Can we please not expose an ad hoc interface for that? As you might have heard the sad news, I'm not feeling up to the task to dig deeper into this right now. Give me a couple of days to look at this with working brain. Thanks, tglx