From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 0EFB2405C4D for ; Fri, 29 May 2026 15:08:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780067317; cv=none; b=lKZBtfkZtatNpfSBHFWsSR4SdqA4MNO9t6EP6mZf8Nypn2Pa8NpM7hduTWXUWykei+bfe3RAL0Qu6WWIXxO6KwlXgBRXunq+OpzmZbNvZHCenMavSGyHUo6PJWSW+KQt/c3nbMyWK7zwkA8SpUYsyMpbQY3izByRVApJO2PR1ic= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780067317; c=relaxed/simple; bh=LpZswxQcTpWpwllCQjxqETaNWjtDeaq0T2fKUuy7APw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=TsRrwKQBlMEXs12hbIrUkIKBp7GCZ2JTAr9ZfERL44Jd8C2kGvTyRqHyv8YPdC9tXdP23dhiRr30sdfStmkeTDPy6MnCg/TGpnJeIy6UjjStWc4yWlmSzFbif7TDZgahWoaUA+K85cy4HiLUMYusIqcLy3f57xPWdBWJYBvSts8= 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=oUCzvPF5; arc=none smtp.client-ip=209.85.216.73 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="oUCzvPF5" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-36ba24fcd46so1263244a91.3 for ; Fri, 29 May 2026 08:08:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1780067315; x=1780672115; darn=vger.kernel.org; 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=NsWUFw3C//DyVpAd+DrRqJ7N44+Z3glyMOS0MZwC4vY=; b=oUCzvPF5D+myYR86G2BjCm78NOQYpRyKvzs4Q90x6pwDO7UbGxsSMbtFqN8eGD4NNi P2Lt9PJtDzVwd61bYQmdV9KO3v1h0G6jL+T4os4C/tmpylK5PjPPvIVJVNAzTY1kE4DE VYF/bD2khyEtJTCiSzvpQQl/OgiZKjMKFec7ATVBK9OvHdpAeKp0q36CM44qqRLjWqi9 J8JoLaGq0rbw6gedoW6+vGqA59nhIE3jBdiS3VNfhtAxMO+qkdYR5Rvfp293M+X13bPj +1pXoLTtxwNhkHdJI5hhR+ZOnp3ZlwiXdW7jthkBR82rBtbJORIwLFBkfSiVtsThTdRa IL5g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780067315; x=1780672115; 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=NsWUFw3C//DyVpAd+DrRqJ7N44+Z3glyMOS0MZwC4vY=; b=E9TO7qTK/BSPM26ER90tY/nTFEgsvat+sadic/4S81DPT4QVr9meZdLMJPSMHVGxpW 4QuXqb68EqoVRzQGHC2GbIc5pu1OijSJFQcwhf+SM+VdzQ2Jh7bOvnH6rVnq0VN+4bGt ETrrB8Uq/eFnMxJPw3HWG/HNsYQSm6H/1FnafFD8oz1ZX5KWb0RcvcNaP3jgswvBrD91 hoN3u5Zn7aPVpG3dGVN6Y7y6Tlo5ETZRWNEQtdQ5JyfoTjBY3ihAtJ+pm/ms1dvF/O+k O+QcwD6TOjzKpJat22VNQiUWTjAGLQxfb9dHFn2lHbA4S0FUpK+WHkymBuM0cGvzTJ+7 7xPg== X-Forwarded-Encrypted: i=1; AFNElJ9v7QvnAJ+XuivtWem+D0ITj0TMmuP3MnEwDpVR9AcZkECFMZLQuLXNHYG+3qtjWJCv4GogyrV3AzsLUBs=@vger.kernel.org X-Gm-Message-State: AOJu0Yzc2zmTN1fwJY4Q7CSBVnWZGeK7lHCUq8QmHQdKYL7N2fcvRWyh 5y6vG0gBZyMbqJeJfbHCfepU2oDggLPyhylnb7ty4dejHZoWJyLL/jm9B1ZYFRkWfnXDbjOVh+v GDCKBQQ== X-Received: from ploo20.prod.google.com ([2002:a17:902:e014:b0:2ba:41dd:4a8e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2bce:b0:2b4:5f96:184d with SMTP id d9443c01a7336-2bf3679ebb8mr2933525ad.5.1780067315192; Fri, 29 May 2026 08:08:35 -0700 (PDT) Reply-To: Sean Christopherson Date: Fri, 29 May 2026 08:08:33 -0700 In-Reply-To: <20260529144435.704127-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260529144435.704127-1-seanjc@google.com> X-Mailer: git-send-email 2.54.0.823.g6e5bcc1fc9-goog Message-ID: <20260529150833.715042-1-seanjc@google.com> Subject: [PATCH v4 46/47] x86/kvmclock: Plumb in AP-online and BSP-resume to kvmlock, for documentation From: Sean Christopherson To: Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , Sean Christopherson , "K . Y . Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , John Stultz Cc: "H . Peter Anvin" , Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, David Woodhouse , Tom Lendacky , Nikunj A Dadhania , David Woodhouse , Michael Kelley , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" Invoke kvmclock_cpu_action() with AP_ONLINE and BSP_RESUME, even though kvmclock doesn't need to do anything in either case, so that the asymmetry of kvmclock is a detail buried in kvmclock, and to explicitly document that doing nothing during those phases is intentional and correct. For all intents and purposes, no functional change intended. Signed-off-by: Sean Christopherson --- arch/x86/include/asm/kvm_para.h | 2 ++ arch/x86/kernel/kvm.c | 22 +++++++++++++------- arch/x86/kernel/kvmclock.c | 37 ++++++++++++++++++++++++++------- 3 files changed, 45 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 08686ff19caa..763ed017738a 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -120,6 +120,8 @@ static inline long kvm_sev_hypercall3(unsigned int nr, unsigned long p1, #ifdef CONFIG_KVM_GUEST enum kvm_guest_cpu_action { KVM_GUEST_BSP_SUSPEND, + KVM_GUEST_BSP_RESUME, + KVM_GUEST_AP_ONLINE, KVM_GUEST_AP_OFFLINE, KVM_GUEST_SHUTDOWN, }; diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index fd1c417b4f9b..2ed4bf13e3ed 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -474,18 +474,24 @@ static void kvm_guest_cpu_offline(enum kvm_guest_cpu_action action) kvmclock_cpu_action(action); } +static void __kvm_cpu_online(unsigned int cpu, enum kvm_guest_cpu_action action) +{ + unsigned long flags; + + local_irq_save(flags); + kvmclock_cpu_action(action); + kvm_guest_cpu_init(); + local_irq_restore(flags); +} + +#ifdef CONFIG_SMP + static int kvm_cpu_online(unsigned int cpu) { - unsigned long flags; - - local_irq_save(flags); - kvm_guest_cpu_init(); - local_irq_restore(flags); + __kvm_cpu_online(cpu, KVM_GUEST_AP_ONLINE); return 0; } -#ifdef CONFIG_SMP - static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask); static bool pv_tlb_flush_supported(void) @@ -750,7 +756,7 @@ static int kvm_suspend(void *data) static void kvm_resume(void *data) { - kvm_cpu_online(raw_smp_processor_id()); + __kvm_cpu_online(raw_smp_processor_id(), KVM_GUEST_BSP_RESUME); #ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL if (kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL) && has_guest_poll) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index cd65ad328637..d122912b8856 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -129,7 +129,7 @@ static void kvm_save_sched_clock_state(void) #ifdef CONFIG_SMP static void kvm_setup_secondary_clock(void) { - kvm_register_clock("secondary cpu clock"); + kvm_register_clock("secondary cpu, startup"); } #endif @@ -153,13 +153,34 @@ static void kvmclock_resume(struct clocksource *cs) void kvmclock_cpu_action(enum kvm_guest_cpu_action action) { - /* - * Don't disable kvmclock on the BSP during suspend. If kvmclock is - * being used for sched_clock, then it needs to be kept alive until the - * last minute, and restored as quickly as possible after resume. - */ - if (action != KVM_GUEST_BSP_SUSPEND) + switch (action) { + /* + * The BSP's clock is managed via clocksource suspend/resume, + * to ensure it's enabled/disabled when timekeeping needs it + * to be, e.g. before reading wallclock (which uses kvmclock). + */ + case KVM_GUEST_BSP_SUSPEND: + case KVM_GUEST_BSP_RESUME: + break; + case KVM_GUEST_AP_ONLINE: + /* + * Secondary CPUs use a dedicated hook to enable kvmclock early + * during bringup, there's nothing to be done during CPU online + * (which runs at CPUHP_AP_ONLINE_DYN). When kvmclock is being + * used as sched_clock, kvmclock must be enabled *very* early, + * and even when kvmclock is "only" being used for the main + * clocksource, it still needs to be enabled long before the + * dynamic CPUHP calls are made. + */ + break; + case KVM_GUEST_AP_OFFLINE: + case KVM_GUEST_SHUTDOWN: kvmclock_disable(); + break; + default: + WARN_ON_ONCE(1); + break; + } } /* @@ -360,7 +381,7 @@ void __init kvmclock_init(bool prefer_tsc) msr_kvm_system_time, msr_kvm_wall_clock); this_cpu_write(hv_clock_per_cpu, &hv_clock_boot[0]); - kvm_register_clock("primary cpu clock"); + kvm_register_clock("primary cpu, online"); pvclock_set_pvti_cpu0_va(hv_clock_boot); if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)) { -- 2.54.0.823.g6e5bcc1fc9-goog