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=-9.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 1253AC2D0DB for ; Wed, 22 Jan 2020 14:22:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CDFFF24676 for ; Wed, 22 Jan 2020 14:22:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="iqwV8vsx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728855AbgAVOWn (ORCPT ); Wed, 22 Jan 2020 09:22:43 -0500 Received: from mail-wr1-f66.google.com ([209.85.221.66]:37110 "EHLO mail-wr1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725871AbgAVOWk (ORCPT ); Wed, 22 Jan 2020 09:22:40 -0500 Received: by mail-wr1-f66.google.com with SMTP id w15so7497966wru.4; Wed, 22 Jan 2020 06:22:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:from:to:cc:subject:date:message-id:in-reply-to:references; bh=D5B46rZepvfhCMrrMr36ldZgrri9BFFr8qCNZvIQpqA=; b=iqwV8vsxeNzwCGX7OOX2fVojc/gPAD7PJLTPV7YPvaX8B4dF9Y11pp4Trrg2hDZ/Ob zDCOp/ueCsg+14zCzGf0o9jsNE7AeArgAVJuuJ22CrjPFFftJYp0ZTcLPwQMZPGJiH5p Nt2rZ0Xjf7aQjzn1g8lS/J+tNjG1hi5ULHF7NocH90YYYHe5rh+/1ZV73jXQa9eRoMCO 8p+SAU4DV+um1JT5ATbQIqPS6Cl9HnFFqNe0AT7Lr0kVsSP0WtguAcja9/g0slXgbxM+ Bzzezvm0NmKwH2Dq4vgATni/bTId8GIFgnVpgejw/QUe/Yf+55wwnkrRXLedP3yn2i9z QJLg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:from:to:cc:subject:date:message-id :in-reply-to:references; bh=D5B46rZepvfhCMrrMr36ldZgrri9BFFr8qCNZvIQpqA=; b=VNBKOik/ix/Eam/BqP/pFmhXZza5s65yDZKjQFs1rqIrUY2RJfRCiNbX2ozgnuLDUK rqOB/p6Q0MuHF1VVegaYOoJ4HfaOZZpxclVCqMm6hu3qOLjvzEOl9iSVAOhvD++666st aFJEOCTzlyHFvhy3ocsQkHc3ZRotCupPgPBUUtQT6Ag2ninfBq7BAOFWFJWDINw9kEaH vPqHeE3Y4+Yve6oW9PwZEul+APrBpfSotXnCZDgvIQOir+gWeTOSSBUGncI15rTcV2bG X9IOLQkvsjwNmQAQYTpuphTO5QCLO5uAaUbtfdA15pRm0+niiOH5NT2J9WZhIrBVWOwJ TPTA== X-Gm-Message-State: APjAAAXkHuTQ1av9lmrjZv3q6xAVQ3pi3ikj1NqpMz8OYxelwGsOn59q n3G72gEGsPBm+qwCdJLe88XEeM+j X-Google-Smtp-Source: APXvYqyNXneQfo1LkZwEKxeux40MUIkj5Kl2DuPRtMcKpilA28SeD40zEziGJOllIoCkMOEkN021Pw== X-Received: by 2002:adf:ce87:: with SMTP id r7mr11384684wrn.245.1579702958228; Wed, 22 Jan 2020 06:22:38 -0800 (PST) Received: from 640k.localdomain ([93.56.166.5]) by smtp.gmail.com with ESMTPSA id x11sm4172282wmg.46.2020.01.22.06.22.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 22 Jan 2020 06:22:37 -0800 (PST) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: mtosatti@redhat.com, stable@vger.kernel.org Subject: [PATCH 2/2] KVM: x86: use raw clock values consistently Date: Wed, 22 Jan 2020 15:22:33 +0100 Message-Id: <1579702953-24184-3-git-send-email-pbonzini@redhat.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1579702953-24184-1-git-send-email-pbonzini@redhat.com> References: <1579702953-24184-1-git-send-email-pbonzini@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 in tkr_mono units, and subtracting tkr_raw units 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 Signed-off-by: Paolo Bonzini --- arch/x86/kvm/x86.c | 38 +++++++++++++++++++++++--------------- 1 file changed, 23 insertions(+), 15 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1b4273cce63c..b5e0648580e1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1577,6 +1577,18 @@ static void update_pvclock_gtod(struct timekeeper *tk) 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) @@ -1590,7 +1602,7 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) int version; int r; struct pvclock_wall_clock wc; - struct timespec64 boot; + u64 wall_nsec; if (!wall_clock) return; @@ -1610,17 +1622,12 @@ static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock) /* * 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)); @@ -1868,7 +1875,7 @@ void kvm_write_tsc(struct kvm_vcpu *vcpu, struct msr_data *msr) 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) { @@ -2206,7 +2213,7 @@ 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; @@ -2222,7 +2229,7 @@ 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(); @@ -2321,7 +2328,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) } 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); @@ -2361,6 +2368,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) 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; @@ -9473,7 +9481,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) 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; -- 1.8.3.1