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 B5413377EA1 for ; Fri, 22 May 2026 10:01:53 +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=1779444117; cv=none; b=WBrFJDjSlfN8/HGyxUe3BwHikUmNZvVBvGHF+/cQ65bWMZnqsgr0iKE1178dWwYYLSVn/nfMlDibTo7ptZTFMsbEhNGLVwuQRgKx+oFEKyOjNnQs1AxujpI+9LvKYanNqc5R2XNAn1DfysAwah66ELZkDWnJ8wovGJcry4LnArA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779444117; c=relaxed/simple; bh=N1Z2oTeoz5GUXF6zvKl/1gBvbXnQzt+/LilOgbVhqm4=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=P9LmY/4sP+OYHvH5wcOtz7FqVUzZxj6hPbFss/aivOUIb95MoeHlmWG30TWkDlbz2IdOFIwNKFYgHisr0ZXO9aSOF4+c6WNP3dCC+xIIe1AxVJYBIsHcFAloyxic+vtI8x0yYheuv0kyufre1tN2t+0ws2AgFTOzz3PUKIBU9VA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (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=CDzy9/6i; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (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="CDzy9/6i" 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=N1Z2oTeoz5GUXF6zvKl/1gBvbXnQzt+/LilOgbVhqm4=; b=CDzy9/6i/vUEstK0+zJ8Ydz3xL emzstNs6u1Rk1yMLtD+C2+T5BqnMkrqBNwPRWhixheNDKluqFyg316bmq1Cg9lYqL1wkszQL707bm dNhfYk12HgS6FRj+deg6haahQApe4bg1rpZ+gyox+p4aKxmlZXtrVQb4JgsbCMBCVG6G2dGTe+8Ye +D7uuT5m5jxW9XDBQRJGPligPEH1xHG+ZTdnSV7Os/HT98ccGeQuh5dDVXi3t7mK4+HznWAY1DkDo 6iso5sY7DFiSgrI+kCK5s50lm2V1h25sTE+AjhEXH5/n8ZaFL2AHa586u03FGpSgpComJMe6Ul61m yWVbzAsQ==; Received: from 54-240-197-238.amazon.com ([54.240.197.238] helo=freeip.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wQMhG-00000009vIj-3rgV; Fri, 22 May 2026 10:01:39 +0000 Message-ID: <00609fa255442648e11e2b5596a3b80a29edcfc8.camel@infradead.org> Subject: Re: [RFC PATCH v2 0/8] timekeeping: Fix draft tracking precision and add feed-forward discipline via vmclock From: David Woodhouse To: Thomas Gleixner , Miroslav Lichvar Cc: Richard Cochran , Wen Gu , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , John Stultz , Stephen Boyd , Anna-Maria Behnsen , Frederic Weisbecker , Shuah Khan , Peter Zijlstra , Thomas =?ISO-8859-1?Q?Wei=DFschuh?= , Arnd Bergmann , Julien Ridoux , Ryan Luu , linux-kernel@vger.kernel.org, Marcelo Tosatti Date: Fri, 22 May 2026 11:01:37 +0100 In-Reply-To: <874ijzvpl8.ffs@tglx> References: <20260517220326.4625-1-dwmw2@infradead.org> <0d32da75fa88c92ac0225ef23a9045afdf2ac9fe.camel@infradead.org> <87o6i8vcni.ffs@tglx> <6c7137748ccea288fdf55e7c2e24817ccc1673ef.camel@infradead.org> <874ijzvpl8.ffs@tglx> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-ZG56Rdr+u4k139q6u1jW" User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-kernel@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 --=-ZG56Rdr+u4k139q6u1jW Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-05-22 at 10:02 +0200, Thomas Gleixner wrote: > On Thu, May 21 2026 at 22:06, David Woodhouse wrote: > > On Thu, 2026-05-21 at 20:30 +0200, Thomas Gleixner wrote: > > >=20 > > > As I said in the other thread, that's just creating yet another priva= te > > > mechanism instead of collecting the counter value together with e.g. > > > CLOCK_REALTIME=C2=A0 > >=20 > > On the plus side, at least he wasn't providing a counter value at *all* > > for the system timestamps, which is better than using a bogus one :) >=20 > At least ... for now :) >=20 > > Can we have a signed-off-by for your ktime_get_snapshot_id() please? >=20 > Are you kidding? That's a PoC to demonstrate how it should be done and > it needs some thought to implement it correctly along with the > get_device_cross_timestamp() one, which is actually not entirely > correct as I noticed a few minutes ago. Obviously. But to take a PoC and then do that thought and turn it into something we can use, it still needs a Co-developed-by: and thus a Signed-off-by: if you would be so kind. > > > or utilizing the PMT correlated one which is available in > > > get_device_crosstime_stamp(). > >=20 > > AFAICT that was the *only* one he was exposing, wasn't it? The vmclock > > driver literally did expose the cycle count used to create the device > > timestamp, which is equivalent to PTM and looked correct for that > > part? >=20 > The vmclock driver lives in it's own made up world, so yes this looks > consistent on the first glance. Heh, the 'made up world' of which you speak is KVM. The older KVM PTP drivers get a CSID_X86_TSC or CSID_ARM_ARCH_COUNTER value too. And they *use* it... and wait, get_device_system_crosststamp() already *does* require the device to generate a system_counterval_t, so your nightmare world where driver authors might pull it out of their posterior *already* exists, doesn't it? And we have things like stmmac which already populate it using CSID_X86_ART. So at least for PTP_SYS_OFFSET_PRECISE, isn't Arthur's patch literally only exporting the same counter values that the driver *already* creates? I'm not quite sure why we have all these histrionics about drivers not being able to create those reliably? Yes, there's plenty to improve as discussed, and we should probably have get_device_system_crosststamp() copy the values from the system_counterval on its local stack into the system_device_crosststamp rather than asking the driver to pass it back through separate fields in the attributes. --=-ZG56Rdr+u4k139q6u1jW 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 nnI9/8Lqpq79tLHYwLajotwLiGTB71AGN5xK+tzB+D4eN9lXayrjcszgbOv2ZCgzExQUAIt98mre 8EggKs9mwtEuKAhYBIP/0K6WsoMnQCcCAwEAAaOCAVwwggFYMBIGA1UdEwEB/wQIMAYBAf8CAQAw HQYDVR0OBBYEFIlICOogTndrhuWByNfhjWSEf/xwMB8GA1UdIwQYMBaAFEXroq/0ksuCMS1Ri6en IZ3zbcgPMA4GA1UdDwEB/wQEAwIBhjAdBgNVHSUEFjAUBggrBgEFBQcDBAYIKwYBBQUHAwIweQYI KwYBBQUHAQEEbTBrMCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5kaWdpY2VydC5jb20wQwYIKwYB BQUHMAKGN2h0dHA6Ly9jYWNlcnRzLmRpZ2ljZXJ0LmNvbS9EaWdpQ2VydEFzc3VyZWRJRFJvb3RD QS5jcnQwRQYDVR0fBD4wPDA6oDigNoY0aHR0cDovL2NybDMuZGlnaWNlcnQuY29tL0RpZ2lDZXJ0 QXNzdXJlZElEUm9vdENBLmNybDARBgNVHSAECjAIMAYGBFUdIAAwDQYJKoZIhvcNAQELBQADggEB ACiagCqvNVxOfSd0uYfJMiZsOEBXAKIR/kpqRp2YCfrP4Tz7fJogYN4fxNAw7iy/bPZcvpVCfe/H /CCcp3alXL0I8M/rnEnRlv8ItY4MEF+2T/MkdXI3u1vHy3ua8SxBM8eT9LBQokHZxGUX51cE0kwa uEOZ+PonVIOnMjuLp29kcNOVnzf8DGKiek+cT51FvGRjV6LbaxXOm2P47/aiaXrDD5O0RF5SiPo6 xD1/ClkCETyyEAE5LRJlXtx288R598koyFcwCSXijeVcRvBB1cNOLEbg7RMSw1AGq14fNe2cH1HG W7xyduY/ydQt6gv5r21mDOQ5SaZSWC/ZRfLDuEYwggWbMIIEg6ADAgECAhAH5JEPagNRXYDiRPdl c1vgMA0GCSqGSIb3DQEBCwUAMEExCzAJBgNVBAYTAkFVMRAwDgYDVQQKEwdWZXJva2V5MSAwHgYD VQQDExdWZXJva2V5IFNlY3VyZSBFbWFpbCBHMjAeFw0yNDEyMzAwMDAwMDBaFw0yODAxMDQyMzU5 NTlaMB4xHDAaBgNVBAMME2R3bXcyQGluZnJhZGVhZC5vcmcwggIiMA0GCSqGSIb3DQEBAQUAA4IC DwAwggIKAoICAQDali7HveR1thexYXx/W7oMk/3Wpyppl62zJ8+RmTQH4yZeYAS/SRV6zmfXlXaZ sNOE6emg8WXLRS6BA70liot+u0O0oPnIvnx+CsMH0PD4tCKSCsdp+XphIJ2zkC9S7/yHDYnqegqt w4smkqUqf0WX/ggH1Dckh0vHlpoS1OoxqUg+ocU6WCsnuz5q5rzFsHxhD1qGpgFdZEk2/c//ZvUN i12vPWipk8TcJwHw9zoZ/ZrVNybpMCC0THsJ/UEVyuyszPtNYeYZAhOJ41vav1RhZJzYan4a1gU0 kKBPQklcpQEhq48woEu15isvwWh9/+5jjh0L+YNaN0I//nHSp6U9COUG9Z0cvnO8FM6PTqsnSbcc 0j+GchwOHRC7aP2t5v2stVx3KbptaYEzi4MQHxm/0+HQpMEVLLUiizJqS4PWPU6zfQTOMZ9uLQRR ci+c5xhtMEBszlQDOvEQcyEG+hc++fH47K+MmZz21bFNfoBxLP6bjR6xtPXtREF5lLXxp+CJ6KKS blPKeVRg/UtyJHeFKAZXO8Zeco7TZUMVHmK0ZZ1EpnZbnAhKE19Z+FJrQPQrlR0gO3lBzuyPPArV hvWxjlO7S4DmaEhLzarWi/ze7EGwWSuI2eEa/8zU0INUsGI4ywe7vepQz7IqaAovAX0d+f1YjbmC VsAwjhLmveFjNwIDAQABo4IBsDCCAawwHwYDVR0jBBgwFoAUiUgI6iBOd2uG5YHI1+GNZIR//HAw HQYDVR0OBBYEFFxiGptwbOfWOtMk5loHw7uqWUOnMDAGA1UdEQQpMCeBE2R3bXcyQGluZnJhZGVh ZC5vcmeBEGRhdmlkQHdvb2Rob3Uuc2UwFAYDVR0gBA0wCzAJBgdngQwBBQEBMA4GA1UdDwEB/wQE AwIF4DAdBgNVHSUEFjAUBggrBgEFBQcDAgYIKwYBBQUHAwQwewYDVR0fBHQwcjA3oDWgM4YxaHR0 cDovL2NybDMuZGlnaWNlcnQuY29tL1Zlcm9rZXlTZWN1cmVFbWFpbEcyLmNybDA3oDWgM4YxaHR0 cDovL2NybDQuZGlnaWNlcnQuY29tL1Zlcm9rZXlTZWN1cmVFbWFpbEcyLmNybDB2BggrBgEFBQcB AQRqMGgwJAYIKwYBBQUHMAGGGGh0dHA6Ly9vY3NwLmRpZ2ljZXJ0LmNvbTBABggrBgEFBQcwAoY0 aHR0cDovL2NhY2VydHMuZGlnaWNlcnQuY29tL1Zlcm9rZXlTZWN1cmVFbWFpbEcyLmNydDANBgkq hkiG9w0BAQsFAAOCAQEAQXc4FPiPLRnTDvmOABEzkIumojfZAe5SlnuQoeFUfi+LsWCKiB8Uextv iBAvboKhLuN6eG/NC6WOzOCppn4mkQxRkOdLNThwMHW0d19jrZFEKtEG/epZ/hw/DdScTuZ2m7im 8ppItAT6GXD3aPhXkXnJpC/zTs85uNSQR64cEcBFjjoQDuSsTeJ5DAWf8EMyhMuD8pcbqx5kRvyt JPsWBQzv1Dsdv2LDPLNd/JUKhHSgr7nbUr4+aAP2PHTXGcEBh8lTeYea9p4d5k969pe0OHYMV5aL xERqTagmSetuIwolkAuBCzA9vulg8Y49Nz2zrpUGfKGOD0FMqenYxdJHgDCCBZswggSDoAMCAQIC EAfkkQ9qA1FdgOJE92VzW+AwDQYJKoZIhvcNAQELBQAwQTELMAkGA1UEBhMCQVUxEDAOBgNVBAoT B1Zlcm9rZXkxIDAeBgNVBAMTF1Zlcm9rZXkgU2VjdXJlIEVtYWlsIEcyMB4XDTI0MTIzMDAwMDAw MFoXDTI4MDEwNDIzNTk1OVowHjEcMBoGA1UEAwwTZHdtdzJAaW5mcmFkZWFkLm9yZzCCAiIwDQYJ KoZIhvcNAQEBBQADggIPADCCAgoCggIBANqWLse95HW2F7FhfH9bugyT/danKmmXrbMnz5GZNAfj Jl5gBL9JFXrOZ9eVdpmw04Tp6aDxZctFLoEDvSWKi367Q7Sg+ci+fH4KwwfQ8Pi0IpIKx2n5emEg nbOQL1Lv/IcNiep6Cq3DiyaSpSp/RZf+CAfUNySHS8eWmhLU6jGpSD6hxTpYKye7PmrmvMWwfGEP WoamAV1kSTb9z/9m9Q2LXa89aKmTxNwnAfD3Ohn9mtU3JukwILRMewn9QRXK7KzM+01h5hkCE4nj W9q/VGFknNhqfhrWBTSQoE9CSVylASGrjzCgS7XmKy/BaH3/7mOOHQv5g1o3Qj/+cdKnpT0I5Qb1 nRy+c7wUzo9OqydJtxzSP4ZyHA4dELto/a3m/ay1XHcpum1pgTOLgxAfGb/T4dCkwRUstSKLMmpL g9Y9TrN9BM4xn24tBFFyL5znGG0wQGzOVAM68RBzIQb6Fz758fjsr4yZnPbVsU1+gHEs/puNHrG0 9e1EQXmUtfGn4InoopJuU8p5VGD9S3Ikd4UoBlc7xl5yjtNlQxUeYrRlnUSmdlucCEoTX1n4UmtA 9CuVHSA7eUHO7I88CtWG9bGOU7tLgOZoSEvNqtaL/N7sQbBZK4jZ4Rr/zNTQg1SwYjjLB7u96lDP sipoCi8BfR35/ViNuYJWwDCOEua94WM3AgMBAAGjggGwMIIBrDAfBgNVHSMEGDAWgBSJSAjqIE53 a4blgcjX4Y1khH/8cDAdBgNVHQ4EFgQUXGIam3Bs59Y60yTmWgfDu6pZQ6cwMAYDVR0RBCkwJ4ET ZHdtdzJAaW5mcmFkZWFkLm9yZ4EQZGF2aWRAd29vZGhvdS5zZTAUBgNVHSAEDTALMAkGB2eBDAEF AQEwDgYDVR0PAQH/BAQDAgXgMB0GA1UdJQQWMBQGCCsGAQUFBwMCBggrBgEFBQcDBDB7BgNVHR8E dDByMDegNaAzhjFodHRwOi8vY3JsMy5kaWdpY2VydC5jb20vVmVyb2tleVNlY3VyZUVtYWlsRzIu Y3JsMDegNaAzhjFodHRwOi8vY3JsNC5kaWdpY2VydC5jb20vVmVyb2tleVNlY3VyZUVtYWlsRzIu Y3JsMHYGCCsGAQUFBwEBBGowaDAkBggrBgEFBQcwAYYYaHR0cDovL29jc3AuZGlnaWNlcnQuY29t MEAGCCsGAQUFBzAChjRodHRwOi8vY2FjZXJ0cy5kaWdpY2VydC5jb20vVmVyb2tleVNlY3VyZUVt YWlsRzIuY3J0MA0GCSqGSIb3DQEBCwUAA4IBAQBBdzgU+I8tGdMO+Y4AETOQi6aiN9kB7lKWe5Ch 4VR+L4uxYIqIHxR7G2+IEC9ugqEu43p4b80LpY7M4KmmfiaRDFGQ50s1OHAwdbR3X2OtkUQq0Qb9 6ln+HD8N1JxO5nabuKbymki0BPoZcPdo+FeRecmkL/NOzzm41JBHrhwRwEWOOhAO5KxN4nkMBZ/w QzKEy4PylxurHmRG/K0k+xYFDO/UOx2/YsM8s138lQqEdKCvudtSvj5oA/Y8dNcZwQGHyVN5h5r2 nh3mT3r2l7Q4dgxXlovERGpNqCZJ624jCiWQC4ELMD2+6WDxjj03PbOulQZ8oY4PQUyp6djF0keA MYIDuzCCA7cCAQEwVTBBMQswCQYDVQQGEwJBVTEQMA4GA1UEChMHVmVyb2tleTEgMB4GA1UEAxMX VmVyb2tleSBTZWN1cmUgRW1haWwgRzICEAfkkQ9qA1FdgOJE92VzW+AwDQYJYIZIAWUDBAIBBQCg ggE3MBgGCSqGSIb3DQEJAzELBgkqhkiG9w0BBwEwHAYJKoZIhvcNAQkFMQ8XDTI2MDUyMjEwMDEz N1owLwYJKoZIhvcNAQkEMSIEIBiNwMmdo7X9kHLbn7ttsbodsovmsEufW0ADLgKiLwYMMGQGCSsG AQQBgjcQBDFXMFUwQTELMAkGA1UEBhMCQVUxEDAOBgNVBAoTB1Zlcm9rZXkxIDAeBgNVBAMTF1Zl cm9rZXkgU2VjdXJlIEVtYWlsIEcyAhAH5JEPagNRXYDiRPdlc1vgMGYGCyqGSIb3DQEJEAILMVeg VTBBMQswCQYDVQQGEwJBVTEQMA4GA1UEChMHVmVyb2tleTEgMB4GA1UEAxMXVmVyb2tleSBTZWN1 cmUgRW1haWwgRzICEAfkkQ9qA1FdgOJE92VzW+AwDQYJKoZIhvcNAQEBBQAEggIAjUOTnUI/Z4Tf r9Hqa/KfoAHW2hKMpJWI4CMtCLZwQCttcyaPkLVr2YWk0xjf0HkiUSYB7X/lGaq+flJNmuinRpTx 5/bQz0shh7Cti7XbN+E0NwEbzLjEjS3oEXjbEdjErvupv3qqW3uWkxwjniKiitVX9WMjknUEvOGA pQGwFclXQRcOMKRASvaUn93nKjNXWpmczDiuQmhs9+jA1YKxGmYpLoOJCpk6NYMFCjU2vR2rF2kj hpzZHZZLhcg2X8cmLqPFa7E6buaRD2e17KVj2U/6AOSlSgLcULvhVla1hUfiPHHYNZ/oK+dCSZjQ wORoiiWg0XAQVmK/2cJOlw4+1MoGGLgfCQFeC7ch+bUakqjgwbh39hDKLykoVK4kaS4aL/dxdfTO Qtjyp07fmppM8gNq2mOAPN//1Is5YwaVq8uXNEeiYiSrGBDXq22aW4RutydHgkOozDZizENCZdM8 XiSztrtUCXb5NqWyWDNqRKGkcbZuH1q6xBeQR2nTt5+3+foQ6TJjpxpWlgwa1iwAWCzzPcIWooo/ T3+crP7kq/SI4yzB8C7DNGARJZ50/xhVMnp1mLKOwAzpIa0Rztq2TTvSiVYoGp2HE3P7ZCInrMpC oqvdgOY9YAq9YtMeHk4RF2xjiU8rejmwnNV7F/PcN4lz8jSnWUvZuSrg6mjsm/IAAAAAAAA= --=-ZG56Rdr+u4k139q6u1jW--