From mboxrd@z Thu Jan 1 00:00:00 1970 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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 DCD94C352A3 for ; Mon, 10 Feb 2020 12:58:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1C4E20714 for ; Mon, 10 Feb 2020 12:58:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581339482; bh=nRKd9XL/nW2DITpoKyhzySLH2ADdGCmEwVeXiXLP8bA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=h6im/FK1rla7p7afSTQ36VAtmn/D0g+b/Qr3NVG+DBcdq357VgzE+9KtkYphw5uqR 5W1KussB9lJWL5eBbztCwL+PtdVzNLXbEbouzxEtlAYgoPIqgFxtq8M3BYZirp5DnH juNW/5ubhQ0dPlVBo73cn15ypu7QquR1BgjUnSxU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730248AbgBJM6C (ORCPT ); Mon, 10 Feb 2020 07:58:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:43130 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729973AbgBJMlW (ORCPT ); Mon, 10 Feb 2020 07:41:22 -0500 Received: from localhost (unknown [209.37.97.194]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7883720838; Mon, 10 Feb 2020 12:41:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581338482; bh=nRKd9XL/nW2DITpoKyhzySLH2ADdGCmEwVeXiXLP8bA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YEya6RCpYktmdcfCHrUA1YVdnsM41F5ruMrbYWOOykpx9Y07n2RAHJZsDEZl/q+PW PbBz6TveiRds4zn9K+OAH902NldZGyovdJ6KeG9VR//C5XPtPt7aIlnRiIuIOPa5hW rAX1ZdawPdlxkLkYKM/t8qXM2E2iJ7xWWoJezaJ0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vitaly Kuznetsov , Paolo Bonzini Subject: [PATCH 5.5 260/367] KVM: x86: use raw clock values consistently Date: Mon, 10 Feb 2020 04:32:53 -0800 Message-Id: <20200210122448.607420692@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200210122423.695146547@linuxfoundation.org> References: <20200210122423.695146547@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Paolo Bonzini commit 8171cd68806bd2fc28ef688e32fb2a3b3deb04e5 upstream. Commit 53fafdbb8b21f ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") changed kvmclock to use tkr_raw instead of tkr_mono. However, the default kvmclock_offset for the VM was still based on the monotonic clock and, if the raw clock drifted enough from the monotonic clock, this could cause a negative system_time to be written to the guest's struct pvclock. RHEL5 does not like it and (if it boots fast enough to observe a negative time value) it hangs. There is another thing to be careful about: getboottime64 returns the host boot time with tkr_mono frequency, and subtracting the tkr_raw-based kvmclock value will cause the wallclock to be off if tkr_raw drifts from tkr_mono. To avoid this, compute the wallclock delta from the current time instead of being clever and using getboottime64. Fixes: 53fafdbb8b21f ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") Cc: stable@vger.kernel.org Reviewed-by: Vitaly Kuznetsov Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/x86.c | 38 +++++++++++++++++++++++--------------- 1 file changed, 23 insertions(+), 15 deletions(-) --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1625,6 +1625,18 @@ static void update_pvclock_gtod(struct t write_seqcount_end(&vdata->seq); } + +static s64 get_kvmclock_base_ns(void) +{ + /* Count up from boot time, but with the frequency of the raw clock. */ + return ktime_to_ns(ktime_add(ktime_get_raw(), pvclock_gtod_data.offs_boot)); +} +#else +static s64 get_kvmclock_base_ns(void) +{ + /* Master clock not used, so we can just use CLOCK_BOOTTIME. */ + return ktime_get_boottime_ns(); +} #endif void kvm_set_pending_timer(struct kvm_vcpu *vcpu) @@ -1638,7 +1650,7 @@ static void kvm_write_wall_clock(struct int version; int r; struct pvclock_wall_clock wc; - struct timespec64 boot; + u64 wall_nsec; if (!wall_clock) return; @@ -1658,17 +1670,12 @@ static void kvm_write_wall_clock(struct /* * The guest calculates current wall clock time by adding * system time (updated by kvm_guest_time_update below) to the - * wall clock specified here. guest system time equals host - * system time for us, thus we must fill in host boot time here. + * wall clock specified here. We do the reverse here. */ - getboottime64(&boot); + wall_nsec = ktime_get_real_ns() - get_kvmclock_ns(kvm); - if (kvm->arch.kvmclock_offset) { - struct timespec64 ts = ns_to_timespec64(kvm->arch.kvmclock_offset); - boot = timespec64_sub(boot, ts); - } - wc.sec = (u32)boot.tv_sec; /* overflow in 2106 guest time */ - wc.nsec = boot.tv_nsec; + wc.nsec = do_div(wall_nsec, 1000000000); + wc.sec = (u32)wall_nsec; /* overflow in 2106 guest time */ wc.version = version; kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc)); @@ -1916,7 +1923,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu raw_spin_lock_irqsave(&kvm->arch.tsc_write_lock, flags); offset = kvm_compute_tsc_offset(vcpu, data); - ns = ktime_get_boottime_ns(); + ns = get_kvmclock_base_ns(); elapsed = ns - kvm->arch.last_tsc_nsec; if (vcpu->arch.virtual_tsc_khz) { @@ -2254,7 +2261,7 @@ u64 get_kvmclock_ns(struct kvm *kvm) spin_lock(&ka->pvclock_gtod_sync_lock); if (!ka->use_master_clock) { spin_unlock(&ka->pvclock_gtod_sync_lock); - return ktime_get_boottime_ns() + ka->kvmclock_offset; + return get_kvmclock_base_ns() + ka->kvmclock_offset; } hv_clock.tsc_timestamp = ka->master_cycle_now; @@ -2270,7 +2277,7 @@ u64 get_kvmclock_ns(struct kvm *kvm) &hv_clock.tsc_to_system_mul); ret = __pvclock_read_cycles(&hv_clock, rdtsc()); } else - ret = ktime_get_boottime_ns() + ka->kvmclock_offset; + ret = get_kvmclock_base_ns() + ka->kvmclock_offset; put_cpu(); @@ -2369,7 +2376,7 @@ static int kvm_guest_time_update(struct } if (!use_master_clock) { host_tsc = rdtsc(); - kernel_ns = ktime_get_boottime_ns(); + kernel_ns = get_kvmclock_base_ns(); } tsc_timestamp = kvm_read_l1_tsc(v, host_tsc); @@ -2409,6 +2416,7 @@ static int kvm_guest_time_update(struct vcpu->hv_clock.tsc_timestamp = tsc_timestamp; vcpu->hv_clock.system_time = kernel_ns + v->kvm->arch.kvmclock_offset; vcpu->last_guest_tsc = tsc_timestamp; + WARN_ON(vcpu->hv_clock.system_time < 0); /* If the host uses TSC clocksource, then it is stable */ pvclock_flags = 0; @@ -9580,7 +9588,7 @@ int kvm_arch_init_vm(struct kvm *kvm, un mutex_init(&kvm->arch.apic_map_lock); spin_lock_init(&kvm->arch.pvclock_gtod_sync_lock); - kvm->arch.kvmclock_offset = -ktime_get_boottime_ns(); + kvm->arch.kvmclock_offset = -get_kvmclock_base_ns(); pvclock_update_vm_gtod_copy(kvm); kvm->arch.guest_can_read_msr_platform_info = true;