From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 2418F21A13487 for ; Thu, 4 May 2017 08:21:09 -0700 (PDT) Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8B9A415561; Thu, 4 May 2017 15:21:08 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 8B9A415561 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=lersek@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 8B9A415561 Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-98.phx2.redhat.com [10.3.116.98]) by smtp.corp.redhat.com (Postfix) with ESMTP id 328A57D95C; Thu, 4 May 2017 15:21:06 +0000 (UTC) To: Gerd Hoffmann References: <1382eb04-9646-133b-9ce5-8293cb54745f@redhat.com> <1493794647.8581.144.camel@redhat.com> <159c4eae-4e13-7958-59f4-dfab4c1bf16e@redhat.com> <1493819062.8581.177.camel@redhat.com> <64591d6f-b5d9-d73d-26a5-4c157b9bd541@redhat.com> <1493909522.371.42.camel@redhat.com> Cc: "Kinney, Michael D" , "Fan, Jeff" , "Yao, Jiewen" , edk2-devel-01 , Paolo Bonzini From: Laszlo Ersek Message-ID: Date: Thu, 4 May 2017 17:21:06 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <1493909522.371.42.camel@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 04 May 2017 15:21:08 +0000 (UTC) Subject: Re: SMRAM sizes on large hosts X-BeenThere: edk2-devel@lists.01.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: EDK II Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 May 2017 15:21:09 -0000 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit On 05/04/17 16:52, Gerd Hoffmann wrote: > Hi, > >> If we invent such a new register, it should be in a location that is >> either read-only, or zeroed-on-reset, in current QEMU. Otherwise, new >> firmware running on old QEMU could be misled by a guest OS that writes >> to this register, and then either reboots or enters S3. > > Good point, we need to be quite careful here to not open security holes. > Current state is that pretty much all pci config space is writable and > not cleared on reset. So no easy way out. > >> ... With this in mind, I don't oppose "having to write somewhere to read >> back the result", but then let's please make that write access as well >> to the same new qemu-specific register, and not to MCH_ESMRAMC. > > That should work, yes. Write '1' to the register, then read back. If > it is still '1' -> no big tseg support. Otherwise it returns the tseg > size in some form, and "11b" in ESMRAMC can be used to pick that. My thoughts exactly! Thank you, Laszlo