From nobody Sat May 30 11:18:25 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass(p=quarantine dis=none) header.from=suse.com ARC-Seal: i=1; a=rsa-sha256; t=1778060163; cv=none; d=zohomail.com; s=zohoarc; b=IwXCL5kqq3LQDNoLPf4m9IxQQ3VTMZuRg9qGQ5NCorW58S4tNSFlZ5gYQKiy/TBNcFXm4Cbei2Ym3aXGSjcZANLHAcPgwEuSZi4TLwYikpJnFk0b2fKUQoNOTdghdaP+036oNavmNbLjbnqrJknLsE6boIuc+hm24CoGCVWtrjs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1778060163; h=Content-Type:Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:Sender:Subject:Subject:To:To:Message-Id:Reply-To; bh=L71mztXwVFtsnyfyfV2aEurTsxFn8kQ6HteBxm3JtcE=; b=NoOMpEk21yEcwHvlXikYaC/LBH+RKUdS3QeORLS/v3M30fMXs+d/NRxSbkGiN49YYWZ4u9/f4bPu3GzS9aYO7tRvzVaCADLPn+rrYGvyQwaW4A7jpkOHZ/JQy3fU4ReWD36UttIhe+SZSI4wZdoUDtNKAVGOD/P4hjt4CK/z8AA= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=pass header.from= (p=quarantine dis=none) Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 17780601630714.380735345140124; Wed, 6 May 2026 02:36:03 -0700 (PDT) Received: from list by lists.xenproject.org with outflank-mailman.1301424.1575706 (Exim 4.92) (envelope-from ) id 1wKYfV-0007Jo-3m; Wed, 06 May 2026 09:35:49 +0000 Received: by outflank-mailman (output) from mailman id 1301424.1575706; Wed, 06 May 2026 09:35:49 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wKYfV-0007Jh-0m; Wed, 06 May 2026 09:35:49 +0000 Received: by outflank-mailman (input) for mailman id 1301424; Wed, 06 May 2026 09:35:48 +0000 Received: from mx.expurgate.net ([195.190.135.10]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1wKYfU-0007JZ-1A for xen-devel@lists.xenproject.org; Wed, 06 May 2026 09:35:48 +0000 Received: from mx.expurgate.net (helo=localhost) by mx.expurgate.net with esmtp id 1wKYfT-008DZC-Cn for xen-devel@lists.xenproject.org; Wed, 06 May 2026 11:35:47 +0200 Received: from [10.42.69.11] (helo=localhost) by localhost with ESMTP (eXpurgate MTA 0.9.1) (envelope-from ) id 69fb0b64-2eae-0a2a0a5409dd-0a2a450badd6-38 for ; Wed, 06 May 2026 11:35:47 +0200 Received: from [209.85.221.41] (helo=mail-wr1-f41.google.com) by tlsNG-42698a.mxtls.expurgate.net with ESMTPS (eXpurgate 4.56.1) (envelope-from ) id 69fb0b73-212f-0a2a450b0019-d155dd29c5a2-3 for ; Wed, 06 May 2026 11:35:47 +0200 Received: by mail-wr1-f41.google.com with SMTP id ffacd0b85a97d-445795cf6f1so3825595f8f.1 for ; Wed, 06 May 2026 02:35:47 -0700 (PDT) Received: from [10.156.60.236] (ip-037-024-206-209.um08.pools.vodafone-ip.de. [37.24.206.209]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45055e2d3d0sm10670559f8f.34.2026.05.06.02.35.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 06 May 2026 02:35:46 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" Authentication-Results: eu.smtp.expurgate.cloud; dkim=pass header.s=google header.d=suse.com header.i="@suse.com" header.h="Content-Transfer-Encoding:Autocrypt:Subject:From:Cc:To:Content-Language:User-Agent:MIME-Version:Date:Message-ID" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=google; t=1778060147; x=1778664947; darn=lists.xenproject.org; h=content-transfer-encoding:autocrypt:subject:from:cc:to :content-language:user-agent:mime-version:date:message-id:from:to:cc :subject:date:message-id:reply-to; bh=L71mztXwVFtsnyfyfV2aEurTsxFn8kQ6HteBxm3JtcE=; b=UkbaDlSiU2eLaKfY4RHVUxF2iDSUTMq0fskqFCBcZHgaamthOKQLHQBoXPhtuuaE6p z2i3rMgBrlY1zVxySDy/PbWtNuvuh2qQUqvkCTjqP9dPa3a+uiKaEO+P2UMzLvoEYeFZ GrOV9FN9RMNFnGiCoF/VcV4cGPHlvYsbMG9eVkmWVYUS4VzOtjoGeo+f3aJ/K6h9Koeg z3Z3DNtj2OYefiadno1z1vh1p2oSXgK7+rTqbA8BkqAQWN2D43IHU4MXQUxGeHNndIpZ en+0endntig4xiUtX976gvUjcqmPx0Yq3E9kcYsoEQPF71cXEeNqMp5gLLfUWjwHdbQ8 trFg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778060147; x=1778664947; h=content-transfer-encoding:autocrypt:subject:from:cc:to :content-language:user-agent:mime-version:date:message-id:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=L71mztXwVFtsnyfyfV2aEurTsxFn8kQ6HteBxm3JtcE=; b=S2S+PEkeuRnkeDjI0ToEDDDO918plDMckRRfPsmu1DMg7c/UzdnNDkLJJ2bRLOvuZS CuQF6HJsbxzi0vT/BXbyzWMxwaPT//SLLSF2jmMH0YY0HmngKk4KIQ4Y/BLcFtrF78CJ 9J5FSWbCyH7PxU32Q622CI7CNPx8gXvdVToO9bSxwyE5aqFTgIHaswNDcuiclD0TbQ74 uvAJdV5GLAZSQBSMFCMrMWVjAZjYyBWnW0T19Wx6nf1/X9Jg4ohdN48Tdon+N3VM5VUp sHJTIjOw7OJPiARJug3fcBnBMIs9tN+/7Z+wuM/r/XZZxMcvjsBqCvp1q+Y6nqTuBk1I ITmg== X-Gm-Message-State: AOJu0YxSFA7tVN5W/8G92LcWZELzfmy6e0fz5qDv2pd7b+yvoTFkmO3a Ng58YXH7N2/OJF9u2gcGiM3aW7dSEOVCBZT+TGfugpJ2h6hem7F524FHDVncTfcxrwIl3zH3oIM 4iOg= X-Gm-Gg: AeBDiesk3ESBTRxXDPjfTzko7thyPnGg4MasfOEAlNvhzBEQEp0sAYiAcFF/NxFh8lC xi49qrtvyUI7UBuaLth8ed9ivQXrEuNGp6C0VGJ0Q9E6yVkuYyjnMUB1dZgcy8qkUT6YW6xu2vs Q4eOm54MnoVQzdThLDn0omS0hGyB6ybz2oiC05oFuUzVJjKMe4j6hjVIKpYtiLnUQTLYMqAgEtr 9d8i9TsiC8ppVLsos7LymF3Ogijq6QA6+9QuZs7UYVr6lgQC1ws4h0OmDSKQB52yNqJA4p8EUjk kvEX15Gd/fHcoJgn66jXXn0s7bZvBgKspLfCQBWBDvwSHnTBLzQ0uDN8R4t1Ha6o3vnmqi37FkP twSj2BgKk2jGXWctBPfxb0r7Z1lXb44wyMDICl/XXfbfUqx6Upfz6+s0DIUenXHO7wUkKd/8nSG ilwuZtaA38rS0maKJR6q+xQYx3c63ga5ZYq0b5uFYo/idJKmlKLYeurAFteXp7wnl4vJYun108Y +gZiSpojU66MkkrbGWyjTQ0pw== X-Received: by 2002:adf:e014:0:20b0:452:273:5cd6 with SMTP id ffacd0b85a97d-45202735d7emr1339868f8f.1.1778060146709; Wed, 06 May 2026 02:35:46 -0700 (PDT) Message-ID: <99a4a514-3ed5-43f7-823c-54771f3bd03d@suse.com> Date: Wed, 6 May 2026 11:35:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Content-Language: en-US To: "xen-devel@lists.xenproject.org" Cc: Andrew Cooper , =?UTF-8?Q?Roger_Pau_Monn=C3=A9?= , Teddy Astie , Nicola Vetrini From: Jan Beulich Subject: [PATCH] x86/time: make do_settime() uses more accurate Autocrypt: addr=jbeulich@suse.com; keydata= xsDiBFk3nEQRBADAEaSw6zC/EJkiwGPXbWtPxl2xCdSoeepS07jW8UgcHNurfHvUzogEq5xk hu507c3BarVjyWCJOylMNR98Yd8VqD9UfmX0Hb8/BrA+Hl6/DB/eqGptrf4BSRwcZQM32aZK 7Pj2XbGWIUrZrd70x1eAP9QE3P79Y2oLrsCgbZJfEwCgvz9JjGmQqQkRiTVzlZVCJYcyGGsD /0tbFCzD2h20ahe8rC1gbb3K3qk+LpBtvjBu1RY9drYk0NymiGbJWZgab6t1jM7sk2vuf0Py O9Hf9XBmK0uE9IgMaiCpc32XV9oASz6UJebwkX+zF2jG5I1BfnO9g7KlotcA/v5ClMjgo6Gl MDY4HxoSRu3i1cqqSDtVlt+AOVBJBACrZcnHAUSuCXBPy0jOlBhxPqRWv6ND4c9PH1xjQ3NP nxJuMBS8rnNg22uyfAgmBKNLpLgAGVRMZGaGoJObGf72s6TeIqKJo/LtggAS9qAUiuKVnygo 3wjfkS9A3DRO+SpU7JqWdsveeIQyeyEJ/8PTowmSQLakF+3fote9ybzd880fSmFuIEJldWxp Y2ggPGpiZXVsaWNoQHN1c2UuY29tPsJgBBMRAgAgBQJZN5xEAhsDBgsJCAcDAgQVAggDBBYC AwECHgECF4AACgkQoDSui/t3IH4J+wCfQ5jHdEjCRHj23O/5ttg9r9OIruwAn3103WUITZee e7Sbg12UgcQ5lv7SzsFNBFk3nEQQCACCuTjCjFOUdi5Nm244F+78kLghRcin/awv+IrTcIWF hUpSs1Y91iQQ7KItirz5uwCPlwejSJDQJLIS+QtJHaXDXeV6NI0Uef1hP20+y8qydDiVkv6l IreXjTb7DvksRgJNvCkWtYnlS3mYvQ9NzS9PhyALWbXnH6sIJd2O9lKS1Mrfq+y0IXCP10eS FFGg+Av3IQeFatkJAyju0PPthyTqxSI4lZYuJVPknzgaeuJv/2NccrPvmeDg6Coe7ZIeQ8Yj t0ARxu2xytAkkLCel1Lz1WLmwLstV30g80nkgZf/wr+/BXJW/oIvRlonUkxv+IbBM3dX2OV8 AmRv1ySWPTP7AAMFB/9PQK/VtlNUJvg8GXj9ootzrteGfVZVVT4XBJkfwBcpC/XcPzldjv+3 HYudvpdNK3lLujXeA5fLOH+Z/G9WBc5pFVSMocI71I8bT8lIAzreg0WvkWg5V2WZsUMlnDL9 mpwIGFhlbM3gfDMs7MPMu8YQRFVdUvtSpaAs8OFfGQ0ia3LGZcjA6Ik2+xcqscEJzNH+qh8V m5jjp28yZgaqTaRbg3M/+MTbMpicpZuqF4rnB0AQD12/3BNWDR6bmh+EkYSMcEIpQmBM51qM EKYTQGybRCjpnKHGOxG0rfFY1085mBDZCH5Kx0cl0HVJuQKC+dV2ZY5AqjcKwAxpE75MLFkr wkkEGBECAAkFAlk3nEQCGwwACgkQoDSui/t3IH7nnwCfcJWUDUFKdCsBH/E5d+0ZnMQi+G0A nAuWpQkjM1ASeQwSHEeAWPgskBQL Content-Transfer-Encoding: quoted-printable X-purgate-ID: tlsNG-42698a/1778060147-19F6EF3B-ACEBE957/0/0 X-purgate-type: clean X-purgate-size: 2801 X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1778060163438158500 Content-Type: text/plain; charset="utf-8" As a comment next to one of the invocations states, get_wallclock_time() can take over a second. The order of evaluation of function arguments is in principle unspecified; in practice at least gcc looks to be evaluating them from last to first. Hence with NOW() invoked first, the respective value passed to do_settime() can be off by over a second (which is in contrast to __get_cmos_time() attempting to get the time exactly after an update, i.e. [pretty] precisely at a seconds boundary). This also addresses a Misra C:2012 rule 13.2 ("The value of an expression and its persistent side-effects shall be the same under all permitted evaluation orders") violation each. Fixes: f64134cdb81c ("x86: Fix time_resume() to notify all domains of wallc= lock change") Fixes: 0bfcf984b727 ("x86: Reintroduce clocksource=3Dtsc") Signed-off-by: Jan Beulich Acked-by: Roger Pau Monn=C3=A9 --- Of course the time it takes to do all the CMOS reads (or whichever else wallclock time source is in use) also results in an inaccuracy. For __get_cmos_time() this might be solvable by having it latch NOW() before doing the 6 reads, but in particular for efi_get_time() there's hardly anything we can do. As to Misra rule 13.2: tagging.ecl lists the rule as clean. I also can't find any deviation for the two instances fixed here. What am I missing? For __get_cmos_time(), tangentially: Wouldn't we better use the century byte if available? As it stands, things will break in 2070. Which is a long way out, yes, but still. (Of course this would mean a 7th slow I/O port write/read pair.) --- a/xen/arch/x86/time.c +++ b/xen/arch/x86/time.c @@ -2575,6 +2575,8 @@ __initcall(verify_tsc_reliability); /* Late init function (after interrupts are enabled). */ int __init init_xen_time(void) { + unsigned long wc; + tsc_check_writability(); =20 open_softirq(TIME_CALIBRATE_SOFTIRQ, local_time_calibration); @@ -2592,7 +2594,8 @@ int __init init_xen_time(void) printk(XENLOG_INFO "Wallclock source: %s\n", wallclock_type_to_string(= )); =20 /* NB. get_wallclock_time() can take over one second to execute. */ - do_settime(get_wallclock_time(), 0, NOW()); + wc =3D get_wallclock_time(); + do_settime(wc, 0, NOW()); =20 /* Finish platform timer initialization. */ try_platform_timer_tail(); @@ -2745,6 +2748,8 @@ int time_suspend(void) =20 int time_resume(void) { + unsigned long wc; + preinit_pit(); =20 resume_platform_timer(); @@ -2756,7 +2761,8 @@ int time_resume(void) =20 set_timer(&calibration_timer, NOW() + EPOCH); =20 - do_settime(get_wallclock_time() + cmos_utc_offset, 0, NOW()); + wc =3D get_wallclock_time(); + do_settime(wc + cmos_utc_offset, 0, NOW()); =20 update_vcpu_system_time(current);