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=-6.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 CED45C433E9 for ; Wed, 3 Feb 2021 09:17:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9049C64F6C for ; Wed, 3 Feb 2021 09:17:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233235AbhBCJRh (ORCPT ); Wed, 3 Feb 2021 04:17:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:26548 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233342AbhBCJRV (ORCPT ); Wed, 3 Feb 2021 04:17:21 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612343755; 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=cJJK3qNERG1luckatuh8Y6BGWPbFjbZumZ5BkOC5HpU=; b=QQmaw9b7fHhaoHBGuEVIGM4feU2P0NS6PYeZh5MDRiY472MEZRE1yt7kMlZkErnSwqjITQ KBUXygJ8L5z+vCQUT+nucAxs3tneL/I8H/5IKSCND8LYhMc+rktjZlXnT/C8uO41Qo1Pmd yc6Ve4wsMZUbe25CeatdpgW6G6z6Dvg= Received: from mail-ej1-f72.google.com (mail-ej1-f72.google.com [209.85.218.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-285-6NkwhtQcND-_rQvMsA5U3A-1; Wed, 03 Feb 2021 04:15:53 -0500 X-MC-Unique: 6NkwhtQcND-_rQvMsA5U3A-1 Received: by mail-ej1-f72.google.com with SMTP id bx12so4334286ejc.15 for ; Wed, 03 Feb 2021 01:15:53 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:in-reply-to:references:date :message-id:mime-version; bh=cJJK3qNERG1luckatuh8Y6BGWPbFjbZumZ5BkOC5HpU=; b=dWYnlwe/XQBlGwdS7f/GMB7I137M46PspBgxsuN/G+bwjum31UnYioUxe2NwybN3gG vvAgwp6iimfD89nlM+OTfhyC/4JbzxAdMVGz5a3si1YEts1VwZibAHjZ5F/rqdBBgc0Y hjeZ5tNvoGQhH1Lf+DPGfPpi7Lu89I84eiphV4IX0TGrPI4PT4S/HEEPLvyZKool98SK oCe/4hFByIwC3w/teuS5tOUKEcNeRS7CfirVgz3INxHi1fyMTuF/79NLCa2I1+beJBdP i23kpEAzwKmmKDb+Cj4U940cKt+NwyobbrtpI0FdTePIqvXH6/X0wmLSQZj3tVDADYi9 tLgQ== X-Gm-Message-State: AOAM530mBc7lXJ2U7np9YwcWukSBXOM+j54fHFR61rZ4UYWrI6KG4m7E hfF1B3L3eo2kkdgu4NdIjmdM/J1iNcRdgFfvqaBr2X7l70mgxc7IYH4pvqKezxBAALpMmdt5wRs 9eBSerFIXuxbE X-Received: by 2002:a05:6402:2029:: with SMTP id ay9mr1938186edb.373.1612343752599; Wed, 03 Feb 2021 01:15:52 -0800 (PST) X-Google-Smtp-Source: ABdhPJzvLXv30MwxASwvybAz0WSIbo63Sp9neFadSuty3raoAfNRSnRLfoYp7EvFM06U1Ux0uQvinw== X-Received: by 2002:a05:6402:2029:: with SMTP id ay9mr1938174edb.373.1612343752464; Wed, 03 Feb 2021 01:15:52 -0800 (PST) Received: from vitty.brq.redhat.com (g-server-2.ign.cz. [91.219.240.2]) by smtp.gmail.com with ESMTPSA id w3sm713171eja.52.2021.02.03.01.15.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 03 Feb 2021 01:15:51 -0800 (PST) From: Vitaly Kuznetsov To: Paolo Bonzini , Kechen Lu Cc: "suravee.suthikulpanit@amd.com" , Somdutta Roy , "kvm@vger.kernel.org" , "qemu-discuss@nongnu.org" Subject: Re: Optimized clocksource with AMD AVIC enabled for Windows guest In-Reply-To: <5688445c-b9c8-dbd6-e9ee-ed40df84f8ca@redhat.com> References: <5688445c-b9c8-dbd6-e9ee-ed40df84f8ca@redhat.com> Date: Wed, 03 Feb 2021 10:15:51 +0100 Message-ID: <878s85pl4o.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Paolo Bonzini writes: > On 03/02/21 07:40, Kechen Lu wrote: >> From the above observations, trying to see if there's a way for >> enabling AVIC while also having the most optimized clock source for >> windows guest. >> > > You would have to change KVM, so that AVIC is only disabled if Auto-EOI > interrupts are used. > (I vaguely recall having this was discussed already but apparently no changes were made since) Hyper-V TLFS defines the following bit: CPUID 0x40000004.EAX Bit 9: Recommend deprecating AutoEOI. But this is merely a recommendation and older Windows versions may not know about the bit and still use it. We need to make sure the bit is set/exposed to Windows guests but we also must track AutoEOI usage and inhibit AVIC when detected. -- Vitaly