From nobody Fri Nov 29 17:45:06 2024 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id C90C9446DB; Tue, 17 Sep 2024 05:39:32 +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=1726551574; cv=none; b=iAAee2wVDXap802taTgbuGeRHGQCzb8uD7T+KfR5YPL0gDoWfA3g8/4fJZ5k1CdqCc7+c1Dq4eyHsdPFy7ZR9aNwd2LUHmIQMM4mZ4iotLWpJovWyaqyZF3QyXCQwTa9pAqbpInqTWR4Nj9pGU5j8QIpXGb6ouNhyafvXBZjrHY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1726551574; c=relaxed/simple; bh=V36Enu6duhfMNTcCMdlRdxzAzxvIq2srIjoMqY92pwg=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=GxKYiVLCz3PD1/oqMsrGd6GVJzgjcvsVriq4oYQRnXsbzS2GN1JYrr3eqsEGcTHpaGl3nz0EU9KdM26kSl1n7o7pwZ0wv3Up9pZ5VVD7bu55e7i2NMYTTJDP54acjkzP6PpdcPqSplPEodrgrLOJ/V573eMXOrkvbr+7VDtpiAo= 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=ZWVwnN9r; 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="ZWVwnN9r" Received: from namjain-Virtual-Machine.mshome.net (unknown [167.220.238.141]) by linux.microsoft.com (Postfix) with ESMTPSA id 6022320C094F; Mon, 16 Sep 2024 22:39:28 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 6022320C094F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1726551572; bh=YkNI0FauVOZ3gmotL9s3DC/8W/JDs9sBlb/S/RNZtEs=; h=From:To:Cc:Subject:Date:From; b=ZWVwnN9rcqiGaxS+uLcz2Rg4C5JwsXSLrycybM3X1p8WlUsuqNqCFP2d6fj3jEITT q9C7Xsp3IdqCOb7EMTTylH4m2QG1MT+LlXC4SfVyx1YRiw/JtV9gg4fAoceDlag4Ga Ry2x5cQvy2DtuMT5eQktok04mZiUFyHH4eTif3Qo= From: Naman Jain To: "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Daniel Lezcano , Michael Kelley Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, namjain@linux.microsoft.com, stable@vger.kernel.org Subject: [PATCH v3] x86/hyper-v: Fix hv tsc page based sched_clock for hibernation Date: Tue, 17 Sep 2024 11:09:17 +0530 Message-Id: <20240917053917.76787-1-namjain@linux.microsoft.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 c= locksource for hibernation") Co-developed-by: Dexuan Cui Signed-off-by: Dexuan Cui Signed-off-by: Naman Jain --- Changes from v2: https://lore.kernel.org/all/20240911045632.3757-1-namjain@linux.microsoft.c= om/ Addressed Michael's comments: * Changed commit msg to include information on making timestamps continuous * Changed subject to reflect the new file being changed * Changed variable name for saving offset/counters * Moved comment on new function introduced from header file to function definition. * Removed the equations in comments * Rebased to latest linux-next tip Changes from v1: https://lore.kernel.org/all/20240909053923.8512-1-namjain@linux.microsoft.c= om/ * Reorganized code as per Michael's comment, and moved the logic to x86 specific files, to keep hyperv_timer.c arch independent. --- 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 ead967479fa6..e8e25d6e64cd 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -224,6 +224,63 @@ static void hv_machine_crash_shutdown(struct pt_regs *= regs) hyperv_cleanup(); } #endif /* CONFIG_CRASH_DUMP */ + +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 resum= e. + */ +static void save_hv_clock_tsc_state(void) +{ + hv_ref_counter_at_suspend =3D 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 =3D reference counter (time) at suspend + * - reference counter (time) now. + */ + hv_adj_sched_clock_offset(hv_ref_counter_at_suspend - hv_read_reference_c= ounter()); +} + +/* + * Functions to override save_sched_clock_state and restore_sched_clock_st= ate + * 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 =3D x86_platform.save_sched_clock_state; + x86_platform.save_sched_clock_state =3D hv_save_sched_clock_state; + + old_restore_sched_clock_state =3D x86_platform.restore_sched_clock_state; + x86_platform.restore_sched_clock_state =3D hv_restore_sched_clock_state; +} #endif /* CONFIG_HYPERV */ =20 static uint32_t __init ms_hyperv_platform(void) @@ -590,6 +647,7 @@ static void __init ms_hyperv_init_platform(void) =20 /* Register Hyper-V specific clocksource */ hv_init_clocksource(); + x86_setup_ops_for_tsc_pg_clock(); hv_vtl_init_platform(); #endif /* diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyper= v_timer.c index 99177835cade..b39dee7b93af 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -27,7 +27,8 @@ #include =20 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; =20 /* * If false, we're using the old mechanism for stimer0 interrupts @@ -470,6 +471,17 @@ static void resume_hv_clock_tsc(struct clocksource *ar= g) hv_set_msr(HV_MSR_REFERENCE_TSC, tsc_msr.as_uint64); } =20 +/* + * Called during resume from hibernation, from overridden + * x86_platform.restore_sched_clock_state routine. This is to adjust offse= ts + * 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 -=3D 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/hyper= v_timer.h index 6cdc873ac907..aa5233b1eba9 100644 --- a/include/clocksource/hyperv_timer.h +++ b/include/clocksource/hyperv_timer.h @@ -38,6 +38,8 @@ extern void hv_remap_tsc_clocksource(void); extern unsigned long hv_get_tsc_pfn(void); extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void); =20 +extern void hv_adj_sched_clock_offset(u64 offset); + static __always_inline bool hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc, u64 *time) base-commit: a430d95c5efa2b545d26a094eb5f624e36732af0 --=20 2.34.1