From patchwork Fri Jul 16 21:26:18 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 12382875 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2B1AC636CB for ; Fri, 16 Jul 2021 21:26:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A7E34613F8 for ; Fri, 16 Jul 2021 21:26:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235965AbhGPV3i (ORCPT ); Fri, 16 Jul 2021 17:29:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52720 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235731AbhGPV3h (ORCPT ); Fri, 16 Jul 2021 17:29:37 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AA021C061760 for ; Fri, 16 Jul 2021 14:26:41 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id 100-20020aed206d0000b029024ea3acef5bso7153879qta.12 for ; Fri, 16 Jul 2021 14:26:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=AaBwmdMcax7XAhpcSLmN0T7h2gkXYZ9weSTQeu17gPo=; b=n+UZtKR+6rwMjkDamlroTQT1ttBiJrUcQcRs/VE3Nhjf2JAT6fCLkDTGNGIp8FgzPw VusNj8z3mvH07JObnhxIPQ+3SMghSjaulZyz8DJyg34ZiyEC0Y0qb5hZUkiPVgl474LN D4pA+u49FGi0CHswynarA8gOGc5NE3PB2qmW0BcwxO5N8YikEnSrz66rM43B16RizxY5 BVCAZf+FwxvYCu2XXQfRr7lwnI/GBm4fqP18lR7om+SE+JdjA3KvkZzPFbwpEBDYSxt+ 9FtzAsJ+WIVdknToyb1OHP4jQOiOGLKNaDwNhhDqnMMZIBBw3bKi9fNiJIo0U4bP0dmV rrlA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=AaBwmdMcax7XAhpcSLmN0T7h2gkXYZ9weSTQeu17gPo=; b=a3uRMbKHhjj4r/FoFxRNauGcoPk923Ox8db6l4bIQkx4wzx9QaSFrnD0NjtcT9LSDd 6J9/c0co391BxY389Smg+YFUqVSxNI21I2I9H9bjgezzpxD5R8WyhQA6ViLSNBzvPMnk HrmDZ3A+W/KY8iJWdACENtbUYnMAmyyzvrc0UUpOPt7OXogkxMY0KuUsV5jX90ieaYwt Yy5eqrwEIz7p/So1uqXyiGgFMaE0db4frdeWoUaEPaoEyAwo61wThOZDelrLGDeBA8v0 gFwu+3WWgHK4voM5sZhgCyIczVjX6gP6drySZIsBSq9pZqx7hR3vDyy+00OZcEEmubr9 j37w== X-Gm-Message-State: AOAM531Ar0U255zE/sxBWFv/qFS9n6FUEjZZlU4F0GjC4pON6J1TIDzq h2mTOZ3HTGgarFjob4dsa+GmgGm53urlez89uElE3J66a7CWysHTSmUtuhB/v8mHylfjrBfytid b4ExIJt6vnqEG5twlQ7fAeU/xeZXPIT80+HnDWEivA0xcid2bfgQGO2QN9w== X-Google-Smtp-Source: ABdhPJw6061a9uMXM1VkCyjmXBdqwqBUUanr8a+oj0D/QBGjbpaBFikl427CiHvVXC3RMqvhmw909LmVLZY= X-Received: from oupton.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:404]) (user=oupton job=sendgmr) by 2002:a05:6214:e4c:: with SMTP id o12mr11576859qvc.18.1626470800724; Fri, 16 Jul 2021 14:26:40 -0700 (PDT) Date: Fri, 16 Jul 2021 21:26:18 +0000 In-Reply-To: <20210716212629.2232756-1-oupton@google.com> Message-Id: <20210716212629.2232756-2-oupton@google.com> Mime-Version: 1.0 References: <20210716212629.2232756-1-oupton@google.com> X-Mailer: git-send-email 2.32.0.402.g57bb445576-goog Subject: [PATCH v2 01/12] KVM: x86: Report host tsc and realtime values in KVM_GET_CLOCK From: Oliver Upton To: kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu Cc: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Peter Shier , Jim Mattson , David Matlack , Ricardo Koller , Jing Zhang , Raghavendra Rao Anata , James Morse , Alexandru Elisei , Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, Oliver Upton Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Handling the migration of TSCs correctly is difficult, in part because Linux does not provide userspace with the ability to retrieve a (TSC, realtime) clock pair for a single instant in time. In lieu of a more convenient facility, KVM can report similar information in the kvm_clock structure. Provide userspace with a host TSC & realtime pair iff the realtime clock is based on the TSC. If userspace provides KVM_SET_CLOCK with a valid realtime value, advance the KVM clock by the amount of elapsed time. Do not step the KVM clock backwards, though, as it is a monotonic oscillator. Suggested-by: Paolo Bonzini Signed-off-by: Oliver Upton Reported-by: kernel test robot Reported-by: kernel test robot Reported-by: kernel test robot --- Documentation/virt/kvm/api.rst | 42 +++++++-- arch/x86/include/asm/kvm_host.h | 3 + arch/x86/kvm/x86.c | 149 ++++++++++++++++++++------------ include/uapi/linux/kvm.h | 7 +- 4 files changed, 137 insertions(+), 64 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index b9ddce5638f5..26bb01a6e82e 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -993,20 +993,34 @@ such as migration. When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the set of bits that KVM can return in struct kvm_clock_data's flag member. -The only flag defined now is KVM_CLOCK_TSC_STABLE. If set, the returned -value is the exact kvmclock value seen by all VCPUs at the instant -when KVM_GET_CLOCK was called. If clear, the returned value is simply -CLOCK_MONOTONIC plus a constant offset; the offset can be modified -with KVM_SET_CLOCK. KVM will try to make all VCPUs follow this clock, -but the exact value read by each VCPU could differ, because the host -TSC is not stable. +FLAGS: + +KVM_CLOCK_TSC_STABLE. If set, the returned value is the exact kvmclock +value seen by all VCPUs at the instant when KVM_GET_CLOCK was called. +If clear, the returned value is simply CLOCK_MONOTONIC plus a constant +offset; the offset can be modified with KVM_SET_CLOCK. KVM will try +to make all VCPUs follow this clock, but the exact value read by each +VCPU could differ, because the host TSC is not stable. + +KVM_CLOCK_REAL_TIME. If set, the `realtime` field in the kvm_clock_data +structure is populated with the value of the host's real time +clocksource at the instant when KVM_GET_CLOCK was called. If clear, +the `realtime` field does not contain a value. + +KVM_CLOCK_HOST_TSC. If set, the `host_tsc` field in the kvm_clock_data +structure is populated with the value of the host's timestamp counter (TSC) +at the instant when KVM_GET_CLOCK was called. If clear, the `host_tsc` field +does not contain a value. :: struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; - __u32 pad[9]; + __u32 pad0; + __u64 realtime; + __u64 host_tsc; + __u32 pad[4]; }; @@ -1023,12 +1037,22 @@ Sets the current timestamp of kvmclock to the value specified in its parameter. In conjunction with KVM_GET_CLOCK, it is used to ensure monotonicity on scenarios such as migration. +FLAGS: + +KVM_CLOCK_REAL_TIME. If set, KVM will compare the value of the `realtime` field +with the value of the host's real time clocksource at the instant when +KVM_SET_CLOCK was called. The difference in elapsed time is added to the final +kvmclock value that will be provided to guests. + :: struct kvm_clock_data { __u64 clock; /* kvmclock current value */ __u32 flags; - __u32 pad[9]; + __u32 pad0; + __u64 realtime; + __u64 host_tsc; + __u32 pad[4]; }; diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 974cbfb1eefe..e527d7259415 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1936,4 +1936,7 @@ int kvm_cpu_dirty_log_size(void); int alloc_all_memslots_rmaps(struct kvm *kvm); +#define KVM_CLOCK_VALID_FLAGS \ + (KVM_CLOCK_TSC_STABLE | KVM_CLOCK_REAL_TIME | KVM_CLOCK_HOST_TSC) + #endif /* _ASM_X86_KVM_HOST_H */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index d715ae9f9108..4e803632cdca 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2780,17 +2780,24 @@ static void kvm_gen_update_masterclock(struct kvm *kvm) #endif } -u64 get_kvmclock_ns(struct kvm *kvm) +/** + * Returns true if realtime and TSC values were written back to the caller. + * Returns false if a clock triplet cannot be obtained, such as if the host's + * realtime clock is not based on the TSC. + */ +static bool get_kvmclock_and_realtime(struct kvm *kvm, u64 *kvmclock_ns, + u64 *realtime_ns, u64 *tsc) { struct kvm_arch *ka = &kvm->arch; struct pvclock_vcpu_time_info hv_clock; unsigned long flags; - u64 ret; + bool ret = false; spin_lock_irqsave(&ka->pvclock_gtod_sync_lock, flags); if (!ka->use_master_clock) { spin_unlock_irqrestore(&ka->pvclock_gtod_sync_lock, flags); - return get_kvmclock_base_ns() + ka->kvmclock_offset; + *kvmclock_ns = get_kvmclock_base_ns() + ka->kvmclock_offset; + return false; } hv_clock.tsc_timestamp = ka->master_cycle_now; @@ -2801,18 +2808,36 @@ u64 get_kvmclock_ns(struct kvm *kvm) get_cpu(); if (__this_cpu_read(cpu_tsc_khz)) { + struct timespec64 ts; + u64 tsc_val; + kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL, &hv_clock.tsc_shift, &hv_clock.tsc_to_system_mul); - ret = __pvclock_read_cycles(&hv_clock, rdtsc()); + + if (kvm_get_walltime_and_clockread(&ts, &tsc_val)) { + *realtime_ns = ts.tv_nsec + NSEC_PER_SEC * ts.tv_sec; + *tsc = tsc_val; + ret = true; + } + + *kvmclock_ns = __pvclock_read_cycles(&hv_clock, tsc_val); } else - ret = get_kvmclock_base_ns() + ka->kvmclock_offset; + *kvmclock_ns = get_kvmclock_base_ns() + ka->kvmclock_offset; put_cpu(); return ret; } +u64 get_kvmclock_ns(struct kvm *kvm) +{ + u64 kvmclock_ns, realtime_ns, tsc; + + get_kvmclock_and_realtime(kvm, &kvmclock_ns, &realtime_ns, &tsc); + return kvmclock_ns; +} + static void kvm_setup_pvclock_page(struct kvm_vcpu *v, struct gfn_to_hva_cache *cache, unsigned int offset) @@ -4031,7 +4056,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_SYNC_X86_VALID_FIELDS; break; case KVM_CAP_ADJUST_CLOCK: - r = KVM_CLOCK_TSC_STABLE; + r = KVM_CLOCK_VALID_FLAGS; break; case KVM_CAP_X86_DISABLE_EXITS: r |= KVM_X86_DISABLE_EXITS_HLT | KVM_X86_DISABLE_EXITS_PAUSE | @@ -5806,6 +5831,68 @@ int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state) } #endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */ +static int kvm_vm_ioctl_get_clock(struct kvm *kvm, + void __user *argp) +{ + struct kvm_clock_data data; + + memset(&data, 0, sizeof(data)); + + if (get_kvmclock_and_realtime(kvm, &data.clock, &data.realtime, + &data.host_tsc)) + data.flags |= KVM_CLOCK_REAL_TIME | KVM_CLOCK_HOST_TSC; + + if (kvm->arch.use_master_clock) + data.flags |= KVM_CLOCK_TSC_STABLE; + + if (copy_to_user(argp, &data, sizeof(data))) + return -EFAULT; + + return 0; +} + +static int kvm_vm_ioctl_set_clock(struct kvm *kvm, + void __user *argp) +{ + struct kvm_arch *ka = &kvm->arch; + struct kvm_clock_data data; + u64 now_raw_ns; + + if (copy_from_user(&data, argp, sizeof(data))) + return -EFAULT; + + if (data.flags & ~KVM_CLOCK_REAL_TIME) + return -EINVAL; + + /* + * TODO: userspace has to take care of races with VCPU_RUN, so + * kvm_gen_update_masterclock() can be cut down to locked + * pvclock_update_vm_gtod_copy(). + */ + kvm_gen_update_masterclock(kvm); + + spin_lock_irq(&ka->pvclock_gtod_sync_lock); + if (data.flags & KVM_CLOCK_REAL_TIME) { + u64 now_real_ns = ktime_get_real_ns(); + + /* + * Avoid stepping the kvmclock backwards. + */ + if (now_real_ns > data.realtime) + data.clock += now_real_ns - data.realtime; + } + + if (ka->use_master_clock) + now_raw_ns = ka->master_kernel_ns; + else + now_raw_ns = get_kvmclock_base_ns(); + ka->kvmclock_offset = data.clock - now_raw_ns; + spin_unlock_irq(&ka->pvclock_gtod_sync_lock); + + kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE); + return 0; +} + long kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg) { @@ -6050,57 +6137,11 @@ long kvm_arch_vm_ioctl(struct file *filp, } #endif case KVM_SET_CLOCK: { - struct kvm_arch *ka = &kvm->arch; - struct kvm_clock_data user_ns; - u64 now_ns; - - r = -EFAULT; - if (copy_from_user(&user_ns, argp, sizeof(user_ns))) - goto out; - - r = -EINVAL; - if (user_ns.flags) - goto out; - - r = 0; - /* - * TODO: userspace has to take care of races with VCPU_RUN, so - * kvm_gen_update_masterclock() can be cut down to locked - * pvclock_update_vm_gtod_copy(). - */ - kvm_gen_update_masterclock(kvm); - - /* - * This pairs with kvm_guest_time_update(): when masterclock is - * in use, we use master_kernel_ns + kvmclock_offset to set - * unsigned 'system_time' so if we use get_kvmclock_ns() (which - * is slightly ahead) here we risk going negative on unsigned - * 'system_time' when 'user_ns.clock' is very small. - */ - spin_lock_irq(&ka->pvclock_gtod_sync_lock); - if (kvm->arch.use_master_clock) - now_ns = ka->master_kernel_ns; - else - now_ns = get_kvmclock_base_ns(); - ka->kvmclock_offset = user_ns.clock - now_ns; - spin_unlock_irq(&ka->pvclock_gtod_sync_lock); - - kvm_make_all_cpus_request(kvm, KVM_REQ_CLOCK_UPDATE); + r = kvm_vm_ioctl_set_clock(kvm, argp); break; } case KVM_GET_CLOCK: { - struct kvm_clock_data user_ns; - u64 now_ns; - - now_ns = get_kvmclock_ns(kvm); - user_ns.clock = now_ns; - user_ns.flags = kvm->arch.use_master_clock ? KVM_CLOCK_TSC_STABLE : 0; - memset(&user_ns.pad, 0, sizeof(user_ns.pad)); - - r = -EFAULT; - if (copy_to_user(argp, &user_ns, sizeof(user_ns))) - goto out; - r = 0; + r = kvm_vm_ioctl_get_clock(kvm, argp); break; } case KVM_MEMORY_ENCRYPT_OP: { diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index d9e4aabcb31a..f2da6760b606 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1223,11 +1223,16 @@ struct kvm_irqfd { /* Do not use 1, KVM_CHECK_EXTENSION returned it before we had flags. */ #define KVM_CLOCK_TSC_STABLE 2 +#define KVM_CLOCK_REAL_TIME (1 << 2) +#define KVM_CLOCK_HOST_TSC (1 << 3) struct kvm_clock_data { __u64 clock; __u32 flags; - __u32 pad[9]; + __u32 pad0; + __u64 realtime; + __u64 host_tsc; + __u32 pad[4]; }; /* For KVM_CAP_SW_TLB */