From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f202.google.com (mail-pf1-f202.google.com [209.85.210.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 10FE939281F for ; Fri, 15 May 2026 19:20:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872835; cv=none; b=fDIy0E29yoEW1kQ9H/IiOLQGE23x45kGO3sp+f7P8trYtNxR6DS27U8xy4WQlXPQ4K6TAHJWLGQrPDMldoW3XCiNbuS8/GOOfFMb2+j0bVyEkIwpE6dF3lYvFa7W3UsIBAMq/CgXc8ukbBPb69GjmmewbuYw3wx69LcXWVPX5II= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778872835; c=relaxed/simple; bh=JiniyiHqLkNeMouNxSmIKJrAhaDkGLDvcienLMupPPk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=E5hIV3qq4lJ1cSLTRxN2bZXAnj1gCpmijPGVGLfuCtOIk75HNnm6Un8LLZGiEGjEHlfqfzUxbcAI0VwEgliPXAqyzAH0ruyxWz8gf9VNMb0eYQJZxi/PPupgZvKskD5mxehnU5BAaAMb+Pd8/5KCNFmiP0oXabnUDCQvTn3CtCE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=JXddG6ab; arc=none smtp.client-ip=209.85.210.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="JXddG6ab" Received: by mail-pf1-f202.google.com with SMTP id d2e1a72fcca58-8353b042152so237122b3a.3 for ; Fri, 15 May 2026 12:20:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1778872832; x=1779477632; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=a7rFpf+FBNzzfzzETx/AclsYanbj3gnBq18rs01MCT0=; b=JXddG6abDDCmdFY/W0LihXHw+X98wbJmGjC7WH6Koj4yvzptFmYwhsBgo6aOHrsNRr qt+IaZir+SbjzVQes/s23FZ8xhhAapZEK8xH7RIspdGZWYbo/QA7nKTQwSdHs1dPOB3F pquR02XAk+a2+0ZxKEZQQyWV/CLaMFf4c405iODIGKA9RigYYxxkI99EbJJf3eeo8bn6 AI/yoBmPXSTeWzPfJVw2JVTv8DGMMvqfx7Dn9I7QZMvqHIsVPG0wutlSNbkK56RlbD/Z E/dVZVZUJvgLqD1tW4ccYVX+GjaYSu0t5zC3cHfGIwhkEugq+cAZzfL82puYYL5rrvhB 5GKQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778872832; x=1779477632; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=a7rFpf+FBNzzfzzETx/AclsYanbj3gnBq18rs01MCT0=; b=XdqvGgmZph49m+cQe7uO0U9SyXznjFyty9AE2x2zYM2y/VmqoflylRe/1b4GRqDLlT zf1IvrFHxpO5c4ionBOqrf3iHZV1fG6O7xgQzoaO780RavUVewlNkQRrEMuSwNBNJteQ Th/HrvmrwscivO7nWPWd6my65uBS6iDEFTmMgS98I+wLl33iC0z4vhrUCXBWq+kFbvml B/4ZnTSE7BnavS2xLAlyb1lZtyeo5oWAOKFxngxQMjOd6J3/4DcNd41UQttpBUXxQcuW LM6352/r1gOKZRUph+YwfZbESPK2nJuXsn6RnXg0lDoLxZgxkFcmRbY1oMU/l/9qomD+ 1M0A== X-Forwarded-Encrypted: i=1; AFNElJ/Nzn0EUULIq4Gggi5vbL+RAvwRvCc5b6SLJRW9HQATS1iIlbghKV0PhiS6RSTyGfVVcHoEUqQQr0z2@lists.linux.dev X-Gm-Message-State: AOJu0Yzudjqiwu5Cm1ale+E7rtMsEdumvGs5QrZfuvDM/9weWuHkiQPK 0Nhn2VJP8KpeR2EuyRZORPaRa8ZvsQdzYmlb9rq1w6ew9+ZRNolDH5g240UbhjRXhnYfvupoEaH wxXEJNg== X-Received: from pfbfk26.prod.google.com ([2002:a05:6a00:3a9a:b0:83e:fb05:9740]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:3689:b0:837:7e7d:3c8 with SMTP id d2e1a72fcca58-83f33df5086mr5912339b3a.39.1778872831848; Fri, 15 May 2026 12:20:31 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 15 May 2026 12:19:08 -0700 In-Reply-To: <20260515191942.1892718-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260515191942.1892718-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.563.g4f69b47b94-goog Message-ID: <20260515191942.1892718-8-seanjc@google.com> Subject: [PATCH v3 07/41] clocksource: hyper-v: Register sched_clock save/restore iff it's necessary From: Sean Christopherson To: Kiryl Shutsemau , Paolo Bonzini , Sean Christopherson , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , Thomas Gleixner , John Stultz Cc: Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , x86@kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Michael Kelley , Tom Lendacky , Nikunj A Dadhania , Thomas Gleixner , David Woodhouse Content-Type: text/plain; charset="UTF-8" Register the Hyper-V reference counter (refcounter) callbacks for saving and restoring its PV sched_clock, if and only if the refcounter is actually being used for sched_clock. Currently, Hyper-V overrides the save/restore hooks if the reference TSC available, whereas the Hyper-V refcounter code only overrides sched_clock if the reference TSC is available *and* it's not invariant. The flaw is effectively papered over by invoking the "old" save/restore callbacks as part of save/restore, but that's unnecessary and fragile. To avoid introducing more complexity, and to allow for additional cleanups of the PV sched_clock code, move the save/restore hooks and logic into hyperv_timer.c and simply wire up the hooks when overriding sched_clock itself. Note, while the Hyper-V refcounter code is intended to be architecture neutral, CONFIG_PARAVIRT is firmly x86-only, i.e. adding a small amount of x86 specific code (which will be reduced in future cleanups) doesn't meaningfully pollute generic code. Reviewed-by: Michael Kelley Tested-by: Michael Kelley Signed-off-by: Sean Christopherson --- arch/x86/kernel/cpu/mshyperv.c | 58 ------------------------------ drivers/clocksource/hyperv_timer.c | 50 ++++++++++++++++++++++++++ 2 files changed, 50 insertions(+), 58 deletions(-) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 8d2401be420c..5ca139ae50b4 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -275,63 +275,6 @@ static void hv_guest_crash_shutdown(struct pt_regs *regs) } #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 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; -} - #ifdef CONFIG_X86_64 DEFINE_STATIC_CALL(hv_hypercall, hv_std_hypercall); EXPORT_STATIC_CALL_TRAMP_GPL(hv_hypercall); @@ -739,7 +682,6 @@ static void __init ms_hyperv_init_platform(void) /* 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/hyperv_timer.c index e9f5034a1bc8..72b966340a46 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -537,10 +537,60 @@ static __always_inline void hv_setup_sched_clock(void *sched_clock) #elif defined CONFIG_PARAVIRT #include +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 __always_inline void hv_setup_sched_clock(void *sched_clock) { /* We're on x86/x64 *and* using PV ops */ paravirt_set_sched_clock(sched_clock); + + 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; } #else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */ static __always_inline void hv_setup_sched_clock(void *sched_clock) {} -- 2.54.0.563.g4f69b47b94-goog