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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 C18DBC4332D for ; Thu, 19 Mar 2020 17:44:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 978452072D for ; Thu, 19 Mar 2020 17:44:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Huno5fMh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728102AbgCSRoe (ORCPT ); Thu, 19 Mar 2020 13:44:34 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:52513 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727310AbgCSRoe (ORCPT ); Thu, 19 Mar 2020 13:44:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1584639872; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nEJ/BlKieSWG5w9g4ZAooVBvmg0v+6w1VOLQ6ao4BaI=; b=Huno5fMh+DeJ3CXA/JCN264dYymJwZyGSi2z9Fztm++DFHhpsi3LuKnhAOWsBsURPDyxlN jfFtVfH2QlPeRTzax0BG00TuI+d2vZN8VkVN4Bn9SYHCc1MZ63CMP8vTdhZbGkEiJZl19H dNesjRzauaz6si0y3zdUSC4AN3dRERU= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-369-5zzJl_7AMI2JXLUlnsrpaQ-1; Thu, 19 Mar 2020 13:44:30 -0400 X-MC-Unique: 5zzJl_7AMI2JXLUlnsrpaQ-1 Received: by mail-wm1-f70.google.com with SMTP id z16so1308798wmi.2 for ; Thu, 19 Mar 2020 10:44:30 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=nEJ/BlKieSWG5w9g4ZAooVBvmg0v+6w1VOLQ6ao4BaI=; b=Fhg6AioSV+FQ9t7kmtdVSdxaQhdN98GsRFx8pprGtbwHICKc8USdw3x04mnxkjPnKu q2Zn6SJ2jdhAmz1GOWjDC4XvWI8rQkcgeSKSbrGWrR3Jy3WbObRQXS41Qo7bFXmFQbwS vMl9kMJq9l5IceSdlBWhQT8qyIdPCkyRwb4nq/sKK9opLVeMtu6DFlZq0y55DRR2Aoah vV4+L5b3C0Qxs3orIt7gq9OLSG7ClXGA/n0l9XF0NUg4fztKgMAdx39qwiJw0ZKXl+kt ZvoOkn5s60fdE9pV2zhzFmBH7s0O0qOPqHIL4V8yNyXoKE87pWsN4ParL3M3PbnfyBeW Vycg== X-Gm-Message-State: ANhLgQ0NF2pF4V8MvVJ4/qJohQVlH4mSwCtpTR4znkdJpQbk04wsHHZh xmLR1WdO8ciFthTN3Nsbn44UtW9M83ez1gKNOrwkh1yucgQ7SWW9iXH+ev29QOqlGx2SwiPALCa INpDqsfYxDv0w1CqJKmJSjR4j X-Received: by 2002:adf:bb06:: with SMTP id r6mr5766081wrg.324.1584639869829; Thu, 19 Mar 2020 10:44:29 -0700 (PDT) X-Google-Smtp-Source: ADFU+vvfLnSZwvyZi0DTLzdUGLabMXyW1faCjMXt0UNAVL0JLf4pVGRQsNCLqsXOTxe3p+rOH+Qizw== X-Received: by 2002:adf:bb06:: with SMTP id r6mr5766051wrg.324.1584639869593; Thu, 19 Mar 2020 10:44:29 -0700 (PDT) Received: from [192.168.178.58] ([151.21.15.43]) by smtp.gmail.com with ESMTPSA id h26sm1623923wmb.19.2020.03.19.10.44.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 19 Mar 2020 10:44:28 -0700 (PDT) Subject: Re: WARNING in vcpu_enter_guest To: Sean Christopherson Cc: syzbot , bp@alien8.de, hpa@zytor.com, jmattson@google.com, joro@8bytes.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, rkrcmar@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, vkuznets@redhat.com, wanpengli@tencent.com, x86@kernel.org References: <000000000000f965b8059877e5e6@google.com> <00000000000081861f05a132b9cd@google.com> <20200319144952.GB11305@linux.intel.com> <20be9560-fce7-1495-3a83-e2b56dbc2389@redhat.com> <20200319173549.GC11305@linux.intel.com> <20200319173927.GD11305@linux.intel.com> From: Paolo Bonzini Message-ID: Date: Thu, 19 Mar 2020 18:44:26 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200319173927.GD11305@linux.intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19/03/20 18:39, Sean Christopherson wrote: >> Yep. I worked through logic/math, mostly to gain a wee bit of knowledge >> about the clock stuff, and it's sound. The KVM_SET_CLOCK from syzkaller >> is simply making time go backwards. > Actually, would it make sense to return -EINVAL for KVM_SET_CLOCK if the > user tries to make kvmclock_offset go backwards? No, it is possible to do that depending on the clock setup on the live migration source. You could cause the warning anyway by setting the clock to a very high (signed) value so that kernel_ns + kvmclock_offset overflows. Paolo