From nobody Wed Dec 17 10:54:38 2025 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E64DBC4167B for ; Mon, 27 Nov 2023 21:35:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233341AbjK0VfU (ORCPT ); Mon, 27 Nov 2023 16:35:20 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230330AbjK0VfS (ORCPT ); Mon, 27 Nov 2023 16:35:18 -0500 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 6999F1B6; Mon, 27 Nov 2023 13:35:25 -0800 (PST) Received: from pmartincic-dev0.corp.microsoft.com (unknown [131.107.159.0]) by linux.microsoft.com (Postfix) with ESMTPSA id BF60D20B74C0; Mon, 27 Nov 2023 13:35:24 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com BF60D20B74C0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1701120924; bh=hzoqjq9Mvw6g9m/hIiSmGN1wXGQ/SBJMNB23AWgjIeg=; h=From:To:Subject:Date:From; b=l1pMr25ZRg/p8Gjj6k84zE69YJqN6NdbZvA+s9oW1dw9U7T13ZNC1BbZRQ7tC/672 XcBj6z5iFz4Nr+HUTOqyNR+STZEktXDAZ76McRqJ+ugZ3LiDYd2q5EgUcOXy+ssCMn 9RS06hXZYPQwlajq+DDI95HaOM3oSpk/JeVl8d0U= From: pmartincic@linux.microsoft.com To: "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] hv_utils: Allow implicit ICTIMESYNCFLAG_SYNC Date: Mon, 27 Nov 2023 13:35:24 -0800 Message-Id: <20231127213524.52783-1-pmartincic@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Peter Martincic Hyper-V hosts can omit the _SYNC flag to due a bug on resume from modern suspend. In such a case, the guest may fail to update its time-of-day to account for the period when it was suspended, and could proceed with a significantly wrong time-of-day. In such a case when the guest is significantly behind, fix it by treating a _SAMPLE the same as if _SYNC was received so that the guest time-of-day is updated. This is hidden behind param hv_utils.timesync_implicit. Signed-off-by: Peter Martincic Acked-by: Boqun Feng --- drivers/hv/hv_util.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 42aec2c5606a..9c97c4065fe7 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -296,6 +296,11 @@ static struct { spinlock_t lock; } host_ts; =20 +static bool timesync_implicit; + +module_param(timesync_implicit, bool, 0644); +MODULE_PARM_DESC(timesync_implicit, "If set treat SAMPLE as SYNC when cloc= k is behind"); + static inline u64 reftime_to_ns(u64 reftime) { return (reftime - WLTIMEDELTA) * 100; @@ -344,6 +349,29 @@ static void hv_set_host_time(struct work_struct *work) do_settimeofday64(&ts); } =20 +/* + * Due to a bug on Hyper-V hosts, the sync flag may not always be sent on = resume. + * Force a sync if the guest is behind. + */ +static inline bool hv_implicit_sync(u64 host_time) +{ + struct timespec64 new_ts; + struct timespec64 threshold_ts; + + new_ts =3D ns_to_timespec64(reftime_to_ns(host_time)); + ktime_get_real_ts64(&threshold_ts); + + threshold_ts.tv_sec +=3D 5; + + /* + * If guest behind the host by 5 or more seconds. + */ + if (timespec64_compare(&new_ts, &threshold_ts) >=3D 0) + return true; + + return false; +} + /* * Synchronize time with host after reboot, restore, etc. * @@ -384,7 +412,8 @@ static inline void adj_guesttime(u64 hosttime, u64 reft= ime, u8 adj_flags) spin_unlock_irqrestore(&host_ts.lock, flags); =20 /* Schedule work to do do_settimeofday64() */ - if (adj_flags & ICTIMESYNCFLAG_SYNC) + if ((adj_flags & ICTIMESYNCFLAG_SYNC) || + (timesync_implicit && hv_implicit_sync(host_ts.host_time))) schedule_work(&adj_time_work); } =20 --=20 2.34.1