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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 A36F9C4361B for ; Tue, 8 Dec 2020 21:36:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AA3523B1F for ; Tue, 8 Dec 2020 21:36:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729924AbgLHVgJ (ORCPT ); Tue, 8 Dec 2020 16:36:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49584 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726104AbgLHVgJ (ORCPT ); Tue, 8 Dec 2020 16:36:09 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CA39EC0613CF; Tue, 8 Dec 2020 13:35:28 -0800 (PST) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1607463327; 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: in-reply-to:in-reply-to:references:references; bh=d8xXDa+xA2WqTiRtB82k0uurlIcN0PDOr9qLhVEuoGw=; b=gV24dbuqb7RWhc6Cs1ie+nYy+k7y5DD4iI0bwsI+ImpsshLl2SYQSx0CfWRK/iwvzzrfu3 66VOoamIeID7TP7zn+DceSrrJkywPK1xjRfjlaibflCt6a0Xidwb+XLR9SShvWYlASvP/H 8Mu+xQszBPPbMruI9xKMvoipcejINjPjVUkqwAPuMLMrihdDxNzXPirzVqhOiSZdyZi+Cx xwPSLMJEBzhmO0Enci9zKWJOwW6FSw+YW5TEAKmu3iZfXL78W99cItlTxlrl7z3BDQhXj+ 9g6f8nAsJt84Utg7P8SvXcf8mbNCBscZpwn13zdNnidpyt7A3IXPN0YTeAL0Uw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1607463327; 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: in-reply-to:in-reply-to:references:references; bh=d8xXDa+xA2WqTiRtB82k0uurlIcN0PDOr9qLhVEuoGw=; b=Dex9IGeygV6lg/lbta/FER8hior4rpg2LfZvtCQMYCSjA8PuPhqou+b4niM2XtQ9b5IJsz sAJoIBR9pH1Sk3Ag== To: Marcelo Tosatti , Maxim Levitsky Cc: kvm@vger.kernel.org, "H. Peter Anvin" , Paolo Bonzini , Jonathan Corbet , Jim Mattson , Wanpeng Li , "open list\:KERNEL SELFTEST FRAMEWORK" , Vitaly Kuznetsov , Sean Christopherson , open list , Ingo Molnar , "maintainer\:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , Joerg Roedel , Borislav Petkov , Shuah Khan , Andrew Jones , Oliver Upton , "open list\:DOCUMENTATION" Subject: Re: [PATCH v2 1/3] KVM: x86: implement KVM_{GET|SET}_TSC_STATE In-Reply-To: <20201208181232.GB31442@fuller.cnet> References: <20201203171118.372391-1-mlevitsk@redhat.com> <20201203171118.372391-2-mlevitsk@redhat.com> <20201207232920.GD27492@fuller.cnet> <05aaabedd4aac7d3bce81d338988108885a19d29.camel@redhat.com> <87sg8g2sn4.fsf@nanos.tec.linutronix.de> <6f64558a029574444da417754786f711c2fec407.camel@redhat.com> <20201208181232.GB31442@fuller.cnet> Date: Tue, 08 Dec 2020 22:35:27 +0100 Message-ID: <87360g2d7k.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Dec 08 2020 at 15:12, Marcelo Tosatti wrote: > On Tue, Dec 08, 2020 at 06:25:13PM +0200, Maxim Levitsky wrote: >> On Tue, 2020-12-08 at 17:02 +0100, Thomas Gleixner wrote: >> The "bug" is that if VMM moves a hardware time counter (tsc or anything else) >> forward by large enough value in one go, >> then the guest kernel will supposingly have an overflow in the time code. >> I don't consider this to be a buggy VMM behavior, but rather a kernel >> bug that should be fixed (if this bug actually exists) > > It exists. In the VMM. >> We are talking about the fact that TSC can jump forward by arbitrary large >> value if the migration took arbitrary amount of time, which >> (assuming that the bug is real) can crash the guest kernel. > > QE reproduced it. Sure, that's what QE is about. Just your conclusion is wrong. Thanks, tglx