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=-2.3 required=3.0 tests=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 7CA97C3A5A1 for ; Thu, 22 Aug 2019 18:03:09 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4DB0A2173E for ; Thu, 22 Aug 2019 18:03:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DB0A2173E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:46932 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0rQS-0000LD-Gx for qemu-devel@archiver.kernel.org; Thu, 22 Aug 2019 14:03:08 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:48152) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i0rNT-0006JZ-6q for qemu-devel@nongnu.org; Thu, 22 Aug 2019 14:00:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i0rNQ-0004uK-RX for qemu-devel@nongnu.org; Thu, 22 Aug 2019 14:00:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1643) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i0rNQ-0004tx-ID for qemu-devel@nongnu.org; Thu, 22 Aug 2019 14:00:00 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A68EC18C8907; Thu, 22 Aug 2019 17:59:59 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (unknown [10.36.118.90]) by smtp.corp.redhat.com (Postfix) with ESMTP id 15ECD5D6A7; Thu, 22 Aug 2019 17:59:30 +0000 (UTC) To: Paolo Bonzini , "Kinney, Michael D" , "rfc@edk2.groups.io" , "Yao, Jiewen" References: <8091f6e8-b1ec-f017-1430-00b0255729f4@redhat.com> <74D8A39837DF1E4DA445A8C0B3885C503F75B680@shsmsx102.ccr.corp.intel.com> <047801f8-624a-2300-3cf7-1daa1395ce59@redhat.com> <99219f81-33a3-f447-95f8-f10341d70084@redhat.com> <6f8b9507-58d0-5fbd-b827-c7194b3b2948@redhat.com> <74D8A39837DF1E4DA445A8C0B3885C503F75FAD3@shsmsx102.ccr.corp.intel.com> <7cb458ea-956e-c1df-33f7-025e4f0f22df@redhat.com> <74D8A39837DF1E4DA445A8C0B3885C503F7600B9@shsmsx102.ccr.corp.intel.com> <20190816161933.7d30a881@x1.home> <74D8A39837DF1E4DA445A8C0B3885C503F761B96@shsmsx102.ccr.corp.intel.com> <35396800-32d2-c25f-b0d0-2d7cd8438687@redhat.com> From: Laszlo Ersek Message-ID: Date: Thu, 22 Aug 2019 19:59:23 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=iso-2022-jp Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.70]); Thu, 22 Aug 2019 17:59:59 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [edk2-rfc] [edk2-devel] CPU hotplug using SMM with QEMU+OVMF X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Chen, Yingwen" , "devel@edk2.groups.io" , Phillip Goerl , qemu devel list , Alex Williamson , "Nakajima, Jun" , Igor Mammedov , Boris Ostrovsky , Joao Marcal Lemos Martins Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 08/21/19 19:05, Paolo Bonzini wrote: > On 21/08/19 17:48, Kinney, Michael D wrote: >> Perhaps there is a way to avoid the 3000:8000 startup >> vector. >> >> If a CPU is added after a cold reset, it is already in a >> different state because one of the active CPUs needs to >> release it by interacting with the hot plug controller. >> >> Can the SMRR for CPUs in that state be pre-programmed to >> match the SMRR in the rest of the active CPUs? >> >> For OVMF we expect all the active CPUs to use the same >> SMRR value, so a check can be made to verify that all >> the active CPUs have the same SMRR value. If they do, >> then any CPU released through the hot plug controller >> can have its SMRR pre-programmed and the initial SMI >> will start within TSEG. >> >> We just need to decide what to do in the unexpected >> case where all the active CPUs do not have the same >> SMRR value. >> >> This should also reduce the total number of steps. > > The problem is not the SMRR but the SMBASE. If the SMBASE area is > outside TSEG, it is vulnerable to DMA attacks independent of the SMRR. > SMBASE is also different for all CPUs, so it cannot be preprogrammed. The firmware and QEMU could agree on a formula, which would compute the CPU-specific SMBASE from a value pre-programmed by the firmware, and the initial APIC ID of the hot-added CPU. Yes, it would duplicate code -- the calculation -- between QEMU and edk2. While that's not optimal, it wouldn't be a first. Thanks Laszlo