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 364B8C64E7B for ; Tue, 1 Dec 2020 13:48:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C209E206F9 for ; Tue, 1 Dec 2020 13:48:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="sCogktfu"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="EQWFj7/b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2391159AbgLANsy (ORCPT ); Tue, 1 Dec 2020 08:48:54 -0500 Received: from Galois.linutronix.de ([193.142.43.55]:55624 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728848AbgLANsx (ORCPT ); Tue, 1 Dec 2020 08:48:53 -0500 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1606830491; 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=X7vkYB0d4Lflu7QTfntzoP7JhOSDHcXUHS8Skey04w0=; b=sCogktfuvGAYAqsR3wllup0MEisJleDTOz/veQFQ3+WxnJh5ZX4IqvTJZsfquxZa8UR+MM eYR4msMoIhJ6BWlKArOBvYfKoEfwq6Dn8oIkTGUUD3jMoFSyDQjwpwbBQYK2ivTaO9DEKi 1eOZm66IhjN8Ln9B8go38cS/815fWJWhQoNlcTJkhadIxm5UYdD7vJUIRXMwtk5JMp4Q8r q9bfjeYpEkyF3N0ptO56wG2lP0g3AP9jUEBkXqVRhvFK1LImRah4VnPO45m89qRBtL57zd 8pRIcB7DAkt5TrjS0YTLIeMX/6qL1RnWJMceKuxFBiFjvu/NOyND+afGhBLK2w== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1606830491; 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=X7vkYB0d4Lflu7QTfntzoP7JhOSDHcXUHS8Skey04w0=; b=EQWFj7/bPK5TaeIVY8G/Qhg8oqXSWyRsTQvYSSfJXMQBySV1McRYlug/Ci1/nRoJkVIorr 3/1MwZ3VqoqmacBA== To: Marcelo Tosatti , Maxim Levitsky Cc: kvm@vger.kernel.org, Paolo Bonzini , Oliver Upton , Ingo Molnar , Sean Christopherson , open list , Jonathan Corbet , Wanpeng Li , Borislav Petkov , Jim Mattson , "H. Peter Anvin" , "open list\:DOCUMENTATION" , Joerg Roedel , "maintainer\:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)" , Vitaly Kuznetsov Subject: Re: [PATCH 0/2] RFC: Precise TSC migration In-Reply-To: <20201130191643.GA18861@fuller.cnet> References: <20201130133559.233242-1-mlevitsk@redhat.com> <20201130191643.GA18861@fuller.cnet> Date: Tue, 01 Dec 2020 14:48:11 +0100 Message-ID: <877dq1hc2s.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 Mon, Nov 30 2020 at 16:16, Marcelo Tosatti wrote: >> Besides, Linux guests don't sync the TSC via IA32_TSC write, >> but rather use IA32_TSC_ADJUST which currently doesn't participate >> in the tsc sync heruistics. > > Linux should not try to sync the TSC with IA32_TSC_ADJUST. It expects > the BIOS to boot with synced TSCs. That's wishful thinking. Reality is that BIOS tinkerers fail to get it right. TSC_ADJUST allows us to undo the wreckage they create. Thanks, tglx