From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: mx.groups.io; dkim=missing; spf=pass (domain: citrix.com, ip: 216.71.155.144, mailfrom: roger.pau@citrix.com) Received: from esa4.hc3370-68.iphmx.com (esa4.hc3370-68.iphmx.com [216.71.155.144]) by groups.io with SMTP; Mon, 15 Jul 2019 07:25:41 -0700 Authentication-Results: esa4.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=roger.pau@citrix.com; spf=Pass smtp.mailfrom=roger.pau@citrix.com; spf=None smtp.helo=postmaster@mail.citrix.com Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender authenticity information available from domain of roger.pau@citrix.com) identity=pra; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="roger.pau@citrix.com"; x-sender="roger.pau@citrix.com"; x-conformance=sidf_compatible Received-SPF: Pass (esa4.hc3370-68.iphmx.com: domain of roger.pau@citrix.com designates 162.221.158.21 as permitted sender) identity=mailfrom; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="roger.pau@citrix.com"; x-sender="roger.pau@citrix.com"; x-conformance=sidf_compatible; x-record-type="v=spf1"; x-record-text="v=spf1 ip4:209.167.231.154 ip4:178.63.86.133 ip4:195.66.111.40/30 ip4:85.115.9.32/28 ip4:199.102.83.4 ip4:192.28.146.160 ip4:192.28.146.107 ip4:216.52.6.88 ip4:216.52.6.188 ip4:162.221.158.21 ip4:162.221.156.83 ~all" Received-SPF: None (esa4.hc3370-68.iphmx.com: no sender authenticity information available from domain of postmaster@mail.citrix.com) identity=helo; client-ip=162.221.158.21; receiver=esa4.hc3370-68.iphmx.com; envelope-from="roger.pau@citrix.com"; x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible IronPort-SDR: skl3wzIQ4gGp8kCSHeZh5/ilDVRW0QRpjweRxcp34eJoc+KBT4ODuHl1As2bgO2WC/ISxxOIq6 iAZeDyPf8WM4tgBbTjAuKi1qiJKUTf54Xmhc1Vh4VVKDujRhlErTxDh2hqCXMvnms7vh5YgI84 2aX6OkhhCgiWCgk+fDNoW3Sosp3YW/Ejovke37sf4W0t0MRNpxaOOhBS+DrkIrZjFRVSPXZTyG Kmv2kvnSbeW9wmd9uJAWUWgyVYM6XcFn8TtcBM4RwoZZRycJnfxPhhCVUX6INRGiYILvz2oHyI qPg= X-SBRS: 2.7 X-MesageID: 3050752 X-Ironport-Server: esa4.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.63,493,1557201600"; d="scan'208";a="3050752" Date: Mon, 15 Jul 2019 16:25:29 +0200 From: =?UTF-8?B?Um9nZXIgUGF1IE1vbm7DqQ==?= To: Andrew Cooper CC: Anthony PERARD , , , Ard Biesheuvel , Jordan Justen , Laszlo Ersek , Julien Grall Subject: Re: [PATCH v3 06/35] OvmfPkg/XenResetVector: Add new entry point for Xen PVH Message-ID: <20190715142529.mekz3mkgc45erv5c@MacBook-Air-de-Roger.local> References: <20190704144233.27968-1-anthony.perard@citrix.com> <20190704144233.27968-7-anthony.perard@citrix.com> <20190715114657.kct664fsiupfbftf@MacBook-Air-de-Roger.local> MIME-Version: 1.0 In-Reply-To: User-Agent: NeoMutt/20180716 Return-Path: roger.pau@citrix.com X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit On Mon, Jul 15, 2019 at 12:50:29PM +0100, Andrew Cooper wrote: > On 15/07/2019 12:46, Roger Pau Monné wrote: > >> + ; > >> + ; Jump to the main routine of the pre-SEC code > >> + ; skiping the 16-bit part of the routine and > >> + ; into the 32-bit flat mode part > >> + ; > >> + OneTimeCallRet TransitionFromReal16To32BitFlat > > Since PVH already starts in flat 32bit mode, I'm not sure I see the > > point of this routine, since it seems to be used exclusively to switch > > from 16 to 32b flat mode. The comment mentions skipping that part, but > > I'm not sure I see how that's achieved. > > Its some OVMF local magic.  This means "jmp > end_of_TransitionFromReal16To32BitFlat", which is the correct place to > go, but the code really is misleading to read. Oh right, it's OneTimeCallRet. I guess this is obvious if you are familiar with OVMF code, which I'm not. Expanding the comment to mention that jumping to the end of the routine is achieved by using OneTimeCallRet would have helped me, but this might be too verbose. Thanks, Roger.