From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 51B5E3176E2; Fri, 15 Aug 2025 18:43:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755283425; cv=none; b=P+TcqNvOtyCgDXYP2xXa0np9r9oSe/xUFVLAfDLQcF4TTgOTZMm4+GeM8zS4IRsLLPMK0OStaMu9NbN04uv4uano0Tx5BCQM5tPEkp5GIE3KEHtR095snAlvhP9SUBo1oSlIw0Bj894uS6arCFU65g+7FZqZoxC/GIAJq8ZYHm0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755283425; c=relaxed/simple; bh=pyUnlgyu1hk7ZXZ6aHZS+qN+Vvwdr9Wy3QvqA9UPYps=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=G7xEvfTgJSOM0iuYwZzT/Ao7qR2mKM5/7lQrYjhI/ToBx0LgsKJ6KLrtf5mIoUp/t/YKISOduGYMbQzKa18lFyb9eCsK4L1x9aZi9xSF4HbCuxjJJwkJLQttFK6b4Q3xyHHVlc6O86fW8wRI4V775to8tsE3Lri/jfa+s7gU6eg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=k6+gIu6o; arc=none smtp.client-ip=90.155.50.34 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=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="k6+gIu6o" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=+5KafjM0IWYE6D2j5vkDAd6Y/Fk3ZDbC1+4dwJEOz9E=; b=k6+gIu6o3MprGSD3gkSziwhSge 4xwN5Fk6xysVPs9bFtKAXQWEQqrQO/J+vooNYGW+j9eoy1txVtkqUFUcvfAfQYvcMalafM4h0q2Fm Haz+jOEkkovbtLL1MKqTfblB2FiICN2ZahCb+QIzQ8NFUTwC1QAA2JhbETVdYIfEA0CSNQKNX65aG badHx95HoC705DWMS+uFoLTusoN/HmBqpUHSTwA7u6q/QViMAfUg/PyjJ/wA90eIZKzVnfzRgsfiQ PdNaZPRkPHAC0jVt0bPQF2tWoTJ8muAmHwLZLWYtpDo7QvliLVAEfnSkzsHq2njOFmvUL4UMUVbeK 5IrXVolg==; Received: from 54-240-197-234.amazon.com ([54.240.197.234] helo=u09cd745991455d.ant.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1umzOo-0000000GE2V-2R42; Fri, 15 Aug 2025 18:43:35 +0000 Message-ID: <0eb8283cfb0de9e4e5fd67b186b8b6c7aab80766.camel@infradead.org> Subject: Re: [PATCH net-next v4] ptp: add Alibaba CIPU PTP clock driver From: David Woodhouse To: Jakub Kicinski , Wen Gu Cc: richardcochran@gmail.com, andrew+netdev@lunn.ch, davem@davemloft.net, edumazet@google.com, pabeni@redhat.com, xuanzhuo@linux.alibaba.com, dust.li@linux.alibaba.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner Date: Fri, 15 Aug 2025 19:43:34 +0100 In-Reply-To: <20250815113814.5e135318@kernel.org> References: <20250812115321.9179-1-guwen@linux.alibaba.com> <20250815113814.5e135318@kernel.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-l9QcHSbBoyq/H+VL+kiA" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html --=-l9QcHSbBoyq/H+VL+kiA Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2025-08-15 at 11:38 -0700, Jakub Kicinski wrote: > On Tue, 12 Aug 2025 19:53:21 +0800 Wen Gu wrote: > > This adds a driver for Alibaba CIPU PTP clock. The CIPU, an underlying > > infrastructure of Alibaba Cloud, synchronizes time with reference clock= s > > continuously and provides PTP clocks for VMs and bare metals in cloud. >=20 > > +static struct attribute *ptp_cipu_attrs[] =3D { > > + &dev_attr_reg_dev_feat.attr, > > + &dev_attr_reg_gst_feat.attr, > > + &dev_attr_reg_drv_ver.attr, > > + &dev_attr_reg_env_ver.attr, > > + &dev_attr_reg_dev_stat.attr, > > + &dev_attr_reg_sync_stat.attr, > > + &dev_attr_reg_tm_prec_ns.attr, > > + &dev_attr_reg_epo_base_yr.attr, > > + &dev_attr_reg_leap_sec.attr, > > + &dev_attr_reg_max_lat_ns.attr, > > + &dev_attr_reg_mt_tout_us.attr, > > + &dev_attr_reg_thresh_us.attr, > > + > > + &dev_attr_ptp_gettm.attr, > > + &dev_attr_ptp_gettm_inval_err.attr, > > + &dev_attr_ptp_gettm_tout_err.attr, > > + &dev_attr_ptp_gettm_excd_thresh.attr, > > + > > + &dev_attr_dev_clk_abn.attr, > > + &dev_attr_dev_clk_abn_rec.attr, > > + &dev_attr_dev_maint.attr, > > + &dev_attr_dev_maint_rec.attr, > > + &dev_attr_dev_maint_tout.attr, > > + &dev_attr_dev_busy.attr, > > + &dev_attr_dev_busy_rec.attr, > > + &dev_attr_dev_err.attr, > > + &dev_attr_dev_err_rec.attr, >=20 > This driver is lacking documentation. You need to describe how the user > is expected to interact with the device and document all these sysfs > attributes. >=20 > Maybe it's just me, but in general I really wish someone stepped up > and created a separate subsystem for all these cloud / vm clocks. > They have nothing to do with PTP. In my mind PTP clocks are simple HW > tickers on which we build all the time related stuff. While this driver > reports the base year for the epoch and leap second status via sysfs. None of it should exist in the cloud anyway. The *only* thing that makes sense for a VM is for the hypervisor to just *tell* the guest what the relationship is between the CPU's hardware counter (e.g. TSC) and real time. Which is what VMclock was invented for. Use that, instead of making *every* guest on the system duplicate the same work of synchronising the *same* underlying oscillator. Badly, with steal time in the mix. Given PCIe PTM to synchronize counters, you could even implement vmclock over PCI for bare metal. --=-l9QcHSbBoyq/H+VL+kiA Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCD9Aw ggSOMIIDdqADAgECAhAOmiw0ECVD4cWj5DqVrT9PMA0GCSqGSIb3DQEBCwUAMGUxCzAJBgNVBAYT AlVTMRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5jb20xJDAi BgNVBAMTG0RpZ2lDZXJ0IEFzc3VyZWQgSUQgUm9vdCBDQTAeFw0yNDAxMzAwMDAwMDBaFw0zMTEx MDkyMzU5NTlaMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYDVQQDExdWZXJv a2V5IFNlY3VyZSBFbWFpbCBHMjCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAMjvgLKj jfhCFqxYyRiW8g3cNFAvltDbK5AzcOaR7yVzVGadr4YcCVxjKrEJOgi7WEOH8rUgCNB5cTD8N/Et GfZI+LGqSv0YtNa54T9D1AWJy08ZKkWvfGGIXN9UFAPMJ6OLLH/UUEgFa+7KlrEvMUupDFGnnR06 aDJAwtycb8yXtILj+TvfhLFhafxroXrflspavejQkEiHjNjtHnwbZ+o43g0/yxjwnarGI3kgcak7 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