From patchwork Wed Aug 4 08:58:00 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Oliver Upton X-Patchwork-Id: 12418159 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=-17.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_ADSP_CUSTOM_MED,DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 D0571C4338F for ; Wed, 4 Aug 2021 09:01:01 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9554360E52 for ; Wed, 4 Aug 2021 09:01:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9554360E52 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:Cc:To:From:Subject:References: Mime-Version:Message-Id:In-Reply-To:Date:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=jasS9M8ko8dq/GIpgRyP8MAwH0uCYg1IiYb6Nao5E50=; b=fON0HFUAQqH+yKjbZLFP9z9hiG LDaxCX+iq11b3IcU83yIRLsqs33824yvsxRIyhl78DEIUoZEztdzeLsZLrCRKQ2sSs2QLaUcx+qyP 5x0YuXVxlNXy+PbEXVUxp7I2y/vKnfmi+9e5LcIBpt4qVQJberMSeCeTvF9ggUxbNcIl5Z+29EhRc WSE29Pa0u+3BpLAd3Ivq3iZ4KpxcAxpVw5gkL/nYNEdkf9kH9N2yc7pbne7W4WAaZH8io2q7xSFk3 IbjMxIcXXbRb/mp8pJfuu5flyY4p4P7BL9iWzHjoRUp+NRV2bujVreBw8CdAY0tFvLmaoJBYthZLQ cTEn4Tdw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBCk6-005FiA-O0; Wed, 04 Aug 2021 08:59:14 +0000 Received: from mail-il1-x14a.google.com ([2607:f8b0:4864:20::14a]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBCjY-005FXd-10 for linux-arm-kernel@lists.infradead.org; Wed, 04 Aug 2021 08:58:41 +0000 Received: by mail-il1-x14a.google.com with SMTP id v18-20020a056e020f92b02901ff388acf98so627211ilo.2 for ; Wed, 04 Aug 2021 01:58:37 -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=K7pLZDgIPuV12HPJ9thky4TOXLt6Z7al5u7GtuvUBZA=; b=by4LiJhYPpMwogtLXJ7fjEm8BONAI58MOYgbyTmmvv9mv9oTtLGatcNERorAuv0dmW UC3XjcBEb+sx3noaVxjS+QVNRj+biM3Lo1eV/RlruKJ50GC+iadfF6aaHguozUNiI3b8 YVhEsnwcNXmmJJqaEt39Vf/k1B6m654tV9mllpPUiOfRIYnAY37fY/gsmCSkNxueDDY4 CHN0wKT96CZGFhb8xqQkHDHbLL8+lrMg5+vDb+3rcZNwb2534M5p+W2BHQjONV2mDibP t5YC7m8i/+Un2HWG0r/tiICiXyhzpxJRCRei0WxRWZFxrCaI8v+wY5+1CvTYu5q7gqWn QVGw== 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=K7pLZDgIPuV12HPJ9thky4TOXLt6Z7al5u7GtuvUBZA=; b=DQxwvocJU71AAA78BVis6gBLmYT60Fj56hqk6n5EiANcj8GkT7s6sDl1zzEklvT0HQ sM4c99Y8dttN/zKGQwS9dIpz2h6iYfqzYAFSfzrWW4hVJGqbAkCNwqIbK1N8o9mliJHb sXBL3m4b8NgFZ42RV2wP8HBC3PwnhqwUrW7Cfd3VTOG2WE6224boVwIcdw/HTSyMrBtP OP640cxGUxn/I3ypxI6bVfvM6uOFVzF+SVRst+vnKwk98lmeCEe8LgNGF8quiYgp5wDG GJwuIHwqHDVU5fQ0Iptj6SdF/hT4mie14hKqyUSks8o/Xe/w/7/6CJ58zoFFO2vHLQ2q HDWg== X-Gm-Message-State: AOAM5320bSxfb+NUz5Pii+t8DEwG99iGH6OzC1F9Yt5gLnAmADgpp8DS SZUz+VD9wylyaBjIHPAmFkS8Snpx8og= X-Google-Smtp-Source: ABdhPJz2W1LC0u615gdgeVlOBMaE1ErBs2fgBK7IpnYekTHQRjIlezwcsg27qu68TXmnKqnX9nsOS4p49MQ= X-Received: from oupton.c.googlers.com ([fda3:e722:ac3:cc00:2b:ff92:c0a8:404]) (user=oupton job=sendgmr) by 2002:a5d:824e:: with SMTP id n14mr394806ioo.134.1628067517220; Wed, 04 Aug 2021 01:58:37 -0700 (PDT) Date: Wed, 4 Aug 2021 08:58:00 +0000 In-Reply-To: <20210804085819.846610-1-oupton@google.com> Message-Id: <20210804085819.846610-3-oupton@google.com> Mime-Version: 1.0 References: <20210804085819.846610-1-oupton@google.com> X-Mailer: git-send-email 2.32.0.605.g8dce9f2422-goog Subject: [PATCH v6 02/21] 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, Andrew Jones , Will Deacon , Catalin Marinas , Oliver Upton X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210804_015840_156898_A7B556DA X-CRM114-Status: GOOD ( 26.60 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 --- Documentation/virt/kvm/api.rst | 42 ++++++++--- arch/x86/include/asm/kvm_host.h | 3 + arch/x86/kvm/x86.c | 127 ++++++++++++++++++-------------- include/uapi/linux/kvm.h | 7 +- 4 files changed, 112 insertions(+), 67 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index dae68e68ca23..8d4a3471ad9e 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_REALTIME. 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_REALTIME. 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 6818095dd157..d6376ca8efce 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1926,4 +1926,7 @@ 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_REALTIME | 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 34287c522f4e..26f1fa263192 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2804,10 +2804,20 @@ static void get_kvmclock(struct kvm *kvm, struct kvm_clock_data *data) get_cpu(); if (__this_cpu_read(cpu_tsc_khz)) { +#ifdef CONFIG_X86_64 + struct timespec64 ts; + + if (kvm_get_walltime_and_clockread(&ts, &data->host_tsc)) { + data->realtime = ts.tv_nsec + NSEC_PER_SEC * ts.tv_sec; + data->flags |= KVM_CLOCK_REALTIME | KVM_CLOCK_HOST_TSC; + } else +#endif + data->host_tsc = rdtsc(); + kvm_get_time_scale(NSEC_PER_SEC, __this_cpu_read(cpu_tsc_khz) * 1000LL, &hv_clock.tsc_shift, &hv_clock.tsc_to_system_mul); - data->clock = __pvclock_read_cycles(&hv_clock, rdtsc()); + data->clock = __pvclock_read_cycles(&hv_clock, data->host_tsc); } else { data->clock = get_kvmclock_base_ns() + ka->kvmclock_offset; } @@ -4047,7 +4057,7 @@ 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 | @@ -5834,6 +5844,60 @@ 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)); + get_kvmclock(kvm, &data); + + 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_REALTIME) + 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_REALTIME) { + 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) { @@ -6077,63 +6141,12 @@ long kvm_arch_vm_ioctl(struct file *filp, break; } #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); + case KVM_SET_CLOCK: + r = kvm_vm_ioctl_set_clock(kvm, argp); break; - } - case KVM_GET_CLOCK: { - struct kvm_clock_data user_ns; - - /* - * Zero flags as it is accessed RMW, leave everything else - * uninitialized as clock is always written and no other fields - * are consumed. - */ - user_ns.flags = 0; - get_kvmclock(kvm, &user_ns); - 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; + case KVM_GET_CLOCK: + r = kvm_vm_ioctl_get_clock(kvm, argp); break; - } case KVM_MEMORY_ENCRYPT_OP: { r = -ENOTTY; if (kvm_x86_ops.mem_enc_op) diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index d9e4aabcb31a..53a49cb8616a 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_REALTIME (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 */