From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6036F20E6 for ; Fri, 3 Jan 2025 05:18:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735881532; cv=none; b=mhHOmu2DhOD608vRwFMl6xmDwYaZhwdax2Rd2bJ0+yxHSB9eGdv8DMDPq6nNgr+D6qvQqTZ7y1uPQSBwdF9oio1wtwRa9O25LJ2+FwOnlCu+zobV/snV+2QUX22+3I4JUX7Cxtrgg1IIa9XNvCZX2qR8rLrlAm69lc6DrYjbUjU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735881532; c=relaxed/simple; bh=G/G2+OJayGY7wFAT6w/dUhKUwiGSEJtGX9LeEqiAJ10=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=bS4/RGxTfJqYpFgVs/R47sDLqkls/X714Mkle8qvQztJ/hBMidpagZHPs+ON6iU4XXfbq/zCMIN7fZK0+z9hv9x4FsI8kByIJ0VfUXdbGhSQgnuVkJwexDZQYE8U1UByjwu6q7nFtm2SfzFrBEL02KCHqZLteLbL7kPZU7bp1GE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=LwW9Zkie; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="LwW9Zkie" Received: from namjain-hibernation.4uyjgaamrtuunfhsycmekme4ua.xx.internal.cloudapp.net (unknown [20.94.232.156]) by linux.microsoft.com (Postfix) with ESMTPSA id DCE132041A91; Thu, 2 Jan 2025 21:18:49 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com DCE132041A91 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1735881529; bh=u69DSVrfmMuKYstmYvBHvP70FYr7lIhUyixV2+epFvk=; h=From:To:Subject:Date:In-Reply-To:References:From; b=LwW9ZkieIYQdgYvvNCO862yGfhfUskLf9uY5rAxPeXOOZOStIn1Z9MZwySR0pKpqw mdBI5CDsBRj6tZPQbzKoyCRoV/UTx79o5aPqX3YbubJNq0rxZsgEhRtcC6rf/EcJ+D dn6qnNbylixnpHKqHzul4HacITjJN55864MatDJY= From: Naman Jain To: stable@vger.kernel.org, namjain@linux.microsoft.com Subject: [PATCH 5.15.y] x86/hyperv: Fix hv tsc page based sched_clock for hibernation Date: Fri, 3 Jan 2025 05:18:45 +0000 Message-ID: <20250103051845.1952-1-namjain@linux.microsoft.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2024122326-eraser-perennial-6b59@gregkh> References: <2024122326-eraser-perennial-6b59@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit read_hv_sched_clock_tsc() assumes that the Hyper-V clock counter is bigger than the variable hv_sched_clock_offset, which is cached during early boot, but depending on the timing this assumption may be false when a hibernated VM starts again (the clock counter starts from 0 again) and is resuming back (Note: hv_init_tsc_clocksource() is not called during hibernation/resume); consequently, read_hv_sched_clock_tsc() may return a negative integer (which is interpreted as a huge positive integer since the return type is u64) and new kernel messages are prefixed with huge timestamps before read_hv_sched_clock_tsc() grows big enough (which typically takes several seconds). Fix the issue by saving the Hyper-V clock counter just before the suspend, and using it to correct the hv_sched_clock_offset in resume. This makes hv tsc page based sched_clock continuous and ensures that post resume, it starts from where it left off during suspend. Override x86_platform.save_sched_clock_state and x86_platform.restore_sched_clock_state routines to correct this as soon as possible. Note: if Invariant TSC is available, the issue doesn't happen because 1) we don't register read_hv_sched_clock_tsc() for sched clock: See commit e5313f1c5404 ("clocksource/drivers/hyper-v: Rework clocksource and sched clock setup"); 2) the common x86 code adjusts TSC similarly: see __restore_processor_state() -> tsc_verify_tsc_adjust(true) and x86_platform.restore_sched_clock_state(). Cc: stable@vger.kernel.org Fixes: 1349401ff1aa ("clocksource/drivers/hyper-v: Suspend/resume Hyper-V clocksource for hibernation") Co-developed-by: Dexuan Cui Signed-off-by: Dexuan Cui Signed-off-by: Naman Jain Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20240917053917.76787-1-namjain@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <20240917053917.76787-1-namjain@linux.microsoft.com> (cherry picked from commit bcc80dec91ee745b3d66f3e48f0ec2efdea97149) Signed-off-by: Naman Jain --- arch/x86/kernel/cpu/mshyperv.c | 58 ++++++++++++++++++++++++++++++ drivers/clocksource/hyperv_timer.c | 14 +++++++- include/clocksource/hyperv_timer.h | 2 ++ 3 files changed, 73 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 3794b223fd69..19762b47fbec 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -150,6 +150,63 @@ static void hv_machine_crash_shutdown(struct pt_regs *regs) hyperv_cleanup(); } #endif /* CONFIG_KEXEC_CORE */ + +static u64 hv_ref_counter_at_suspend; +static void (*old_save_sched_clock_state)(void); +static void (*old_restore_sched_clock_state)(void); + +/* + * Hyper-V clock counter resets during hibernation. Save and restore clock + * offset during suspend/resume, while also considering the time passed + * before suspend. This is to make sure that sched_clock using hv tsc page + * based clocksource, proceeds from where it left off during suspend and + * it shows correct time for the timestamps of kernel messages after resume. + */ +static void save_hv_clock_tsc_state(void) +{ + hv_ref_counter_at_suspend = hv_read_reference_counter(); +} + +static void restore_hv_clock_tsc_state(void) +{ + /* + * Adjust the offsets used by hv tsc clocksource to + * account for the time spent before hibernation. + * adjusted value = reference counter (time) at suspend + * - reference counter (time) now. + */ + hv_adj_sched_clock_offset(hv_ref_counter_at_suspend - hv_read_reference_counter()); +} + +/* + * Functions to override save_sched_clock_state and restore_sched_clock_state + * functions of x86_platform. The Hyper-V clock counter is reset during + * suspend-resume and the offset used to measure time needs to be + * corrected, post resume. + */ +static void hv_save_sched_clock_state(void) +{ + old_save_sched_clock_state(); + save_hv_clock_tsc_state(); +} + +static void hv_restore_sched_clock_state(void) +{ + restore_hv_clock_tsc_state(); + old_restore_sched_clock_state(); +} + +static void __init x86_setup_ops_for_tsc_pg_clock(void) +{ + if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) + return; + + old_save_sched_clock_state = x86_platform.save_sched_clock_state; + x86_platform.save_sched_clock_state = hv_save_sched_clock_state; + + old_restore_sched_clock_state = x86_platform.restore_sched_clock_state; + x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state; +} #endif /* CONFIG_HYPERV */ static uint32_t __init ms_hyperv_platform(void) @@ -438,6 +495,7 @@ static void __init ms_hyperv_init_platform(void) /* Register Hyper-V specific clocksource */ hv_init_clocksource(); + x86_setup_ops_for_tsc_pg_clock(); #endif /* * TSC should be marked as unstable only after Hyper-V diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c index bb47610bbd1c..66cf3d7468e5 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -26,7 +26,8 @@ #include static struct clock_event_device __percpu *hv_clock_event; -static u64 hv_sched_clock_offset __ro_after_init; +/* Note: offset can hold negative values after hibernation. */ +static u64 hv_sched_clock_offset __read_mostly; /* * If false, we're using the old mechanism for stimer0 interrupts @@ -416,6 +417,17 @@ static void resume_hv_clock_tsc(struct clocksource *arg) hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr); } +/* + * Called during resume from hibernation, from overridden + * x86_platform.restore_sched_clock_state routine. This is to adjust offsets + * used to calculate time for hv tsc page based sched_clock, to account for + * time spent before hibernation. + */ +void hv_adj_sched_clock_offset(u64 offset) +{ + hv_sched_clock_offset -= offset; +} + #ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK static int hv_cs_enable(struct clocksource *cs) { diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h index b3f5d73ae1d6..6668e92b1cc4 100644 --- a/include/clocksource/hyperv_timer.h +++ b/include/clocksource/hyperv_timer.h @@ -34,6 +34,8 @@ extern void hv_init_clocksource(void); extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void); +extern void hv_adj_sched_clock_offset(u64 offset); + static inline notrace u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc) { -- 2.43.0