From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <lersek@redhat.com>
Received-SPF: Pass (sender SPF authorized) identity=mailfrom;
 client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=lersek@redhat.com;
 receiver=edk2-devel@lists.01.org 
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 10C462118C51F
 for <edk2-devel@lists.01.org>; Wed,  7 Nov 2018 05:36:43 -0800 (PST)
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 8BBCCC07015A;
 Wed,  7 Nov 2018 13:36:42 +0000 (UTC)
Received: from lacos-laptop-7.usersys.redhat.com (ovpn-120-90.rdu2.redhat.com
 [10.10.120.90])
 by smtp.corp.redhat.com (Postfix) with ESMTP id 83B7860472;
 Wed,  7 Nov 2018 13:36:41 +0000 (UTC)
To: "Yao, Jiewen" <jiewen.yao@intel.com>
Cc: "Ni, Ruiyu" <ruiyu.ni@intel.com>,
 "edk2-devel@lists.01.org" <edk2-devel@lists.01.org>,
 "Dong, Eric" <eric.dong@intel.com>
References: <20181106025935.102620-1-ruiyu.ni@intel.com>
 <de5d784b-ce40-6f18-8797-96a36041aadb@redhat.com>
 <4F047944-D550-432F-9A60-451D9772FE43@intel.com>
 <74D8A39837DF1E4DA445A8C0B3885C503F3D8305@shsmsx102.ccr.corp.intel.com>
From: Laszlo Ersek <lersek@redhat.com>
Message-ID: <ab1ad449-1a03-2901-93d7-bf01af24901e@redhat.com>
Date: Wed, 7 Nov 2018 14:36:40 +0100
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: <74D8A39837DF1E4DA445A8C0B3885C503F3D8305@shsmsx102.ccr.corp.intel.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 [10.5.110.31]); Wed, 07 Nov 2018 13:36:42 +0000 (UTC)
Subject: Re: [PATCH] UefiCpuPkg/SmmCpu: Block SMM read-out only when static paging is used
X-BeenThere: edk2-devel@lists.01.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: EDK II Development  <edk2-devel.lists.01.org>
List-Unsubscribe: <https://lists.01.org/mailman/options/edk2-devel>,
 <mailto:edk2-devel-request@lists.01.org?subject=unsubscribe>
List-Archive: <http://lists.01.org/pipermail/edk2-devel/>
List-Post: <mailto:edk2-devel@lists.01.org>
List-Help: <mailto:edk2-devel-request@lists.01.org?subject=help>
List-Subscribe: <https://lists.01.org/mailman/listinfo/edk2-devel>,
 <mailto:edk2-devel-request@lists.01.org?subject=subscribe>
X-List-Received-Date: Wed, 07 Nov 2018 13:36:44 -0000
Content-Type: text/plain; charset=windows-1252
Content-Language: en-US
Content-Transfer-Encoding: 7bit

On 11/07/18 09:27, Yao, Jiewen wrote:
> If Static paging is not used, then the SMM uses dynamic paging.
> 
> Here dynamic paging means the page fault request on-demand.
> 
> 2 special examples here:
> 1) above 4G MMIO. By default, SMM only setup paging table for 4G memory. If MMIO above 4G, then SMM need use #PF handler to grant MMIO access.
> 2) server RAS. By default, SMM only setup paging table for SMM communication buffer. For server RAS, memory hotplug may request direct OS memory access. If so, we also rely on #PF handler to grant OS access.
> 
> This patch fixed the second issue in the second case.

This is very interesting -- if you have a bit of time, can you please
describe in more detail what "For server RAS, memory hotplug may request
direct OS memory access" means? What agents take what steps?

(I don't mean to hold this patch -- I've given my A-b, so this is for my
own education only. Although, adding this very useful info to the commit
message, or at least to the associated BZ, would be extremely useful.)

Thanks!
Laszlo