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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 54A0013F6DFF for ; Mon, 30 Jul 2018 09:15:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B9B6620873 for ; Mon, 30 Jul 2018 09:14:59 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B9B6620873 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726692AbeG3KtA (ORCPT ); Mon, 30 Jul 2018 06:49:00 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:57700 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726561AbeG3Ks7 (ORCPT ); Mon, 30 Jul 2018 06:48:59 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 17B497C6A9; Mon, 30 Jul 2018 09:14:57 +0000 (UTC) Received: from vitty.brq.redhat.com.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CB3662026D68; Mon, 30 Jul 2018 09:14:55 +0000 (UTC) From: Vitaly Kuznetsov To: Paolo Bonzini Cc: Jim Mattson , kvm list , Radim =?utf-8?B?S3LEjW3DocWZ?= , the arch/x86 maintainers , LKML Subject: Re: [PATCH RFC] x86/kvm/lapic: always disable MMIO interface in x2APIC mode References: <20180727144448.9606-1-vkuznets@redhat.com> Date: Mon, 30 Jul 2018 11:14:54 +0200 In-Reply-To: (Paolo Bonzini's message of "Fri, 27 Jul 2018 19:00:38 +0200") Message-ID: <87sh41nkz5.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.78 on 10.11.54.4 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 30 Jul 2018 09:14:57 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.2]); Mon, 30 Jul 2018 09:14:57 +0000 (UTC) for IP:'10.11.54.4' DOMAIN:'int-mx04.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'vkuznets@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Paolo Bonzini writes: > On 27/07/2018 18:48, Jim Mattson wrote: >> On a physical machine, I would expect the default local APIC page to >> fall in the PCI hole, so it would be correct to sink writes and to >> return all ones for reads. Does qemu implement a PCI hole, and does >> this address fall into it? > > It does implement a PCI hole, but when using the kernel LAPIC it expects > that only devices write to that range; therefore that address doesn't > fall into the PCI hole, and instead it generates an MSIs. Yes, and that's why I believe it's correct to never forward lapic reads/writes from KVM to userspace when lapic is in kernel. "RFC" was mostly about the inconsistency with the case when APIC access page is in use. To be 100% correct I would suggest to somehow make it behave like MMIO hole in case we're in x2APIC/disabled mode too. -- Vitaly