From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: mx.groups.io; dkim=missing; spf=pass (domain: citrix.com, ip: 216.71.155.175, mailfrom: anthony.perard@citrix.com) Received: from esa6.hc3370-68.iphmx.com (esa6.hc3370-68.iphmx.com [216.71.155.175]) by groups.io with SMTP; Fri, 19 Jul 2019 08:51:07 -0700 Authentication-Results: esa6.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=anthony.perard@citrix.com; spf=Pass smtp.mailfrom=anthony.perard@citrix.com; spf=None smtp.helo=postmaster@mail.citrix.com Received-SPF: None (esa6.hc3370-68.iphmx.com: no sender authenticity information available from domain of anthony.perard@citrix.com) identity=pra; client-ip=162.221.158.21; receiver=esa6.hc3370-68.iphmx.com; envelope-from="anthony.perard@citrix.com"; x-sender="anthony.perard@citrix.com"; x-conformance=sidf_compatible Received-SPF: Pass (esa6.hc3370-68.iphmx.com: domain of anthony.perard@citrix.com designates 162.221.158.21 as permitted sender) identity=mailfrom; client-ip=162.221.158.21; receiver=esa6.hc3370-68.iphmx.com; envelope-from="anthony.perard@citrix.com"; x-sender="anthony.perard@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 (esa6.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=esa6.hc3370-68.iphmx.com; envelope-from="anthony.perard@citrix.com"; x-sender="postmaster@mail.citrix.com"; x-conformance=sidf_compatible IronPort-SDR: ZH0/skXZOYFpc1O54m1nnR95vnRkUwSd3KLwkgt8gePTgKAm4XiM5aBHCZAeoyPub+QYA4ccpe a4NmXv9WIK4uB8jzouoTNsfG+JhmazyGCbBDMgJnQc05PIf6OKDqLV2ao/Du9K6r284LM6WQ6m UG2Y/uJjh9aTqCyVZBYbjGJunR7D6mLIJoS3E0IT+85GmOR8CABBC+URC4UkbpFR9hY+QgU/st HGTfA5csX4F0vD7KPHPVxMHMRaN007T2mOcMcXsg8vBPFzpvBonWGi63ZiqkIPPzvuBLUFyFOy Qi0= X-SBRS: 2.7 X-MesageID: 3281444 X-Ironport-Server: esa6.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.64,283,1559534400"; d="scan'208";a="3281444" Date: Fri, 19 Jul 2019 16:51:04 +0100 From: "Anthony PERARD" To: Andrew Cooper CC: Laszlo Ersek , , , Ard Biesheuvel , Jordan Justen , Julien Grall , Roger Pau =?iso-8859-1?Q?Monn=E9?= Subject: Re: [PATCH v3 06/35] OvmfPkg/XenResetVector: Add new entry point for Xen PVH Message-ID: <20190719155104.GD1208@perard.uk.xensource.com> References: <20190704144233.27968-1-anthony.perard@citrix.com> <20190704144233.27968-7-anthony.perard@citrix.com> <20190719102008.GB1208@perard.uk.xensource.com> <03cc01a5-d6a8-84b7-d382-d83fadea486b@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Return-Path: anthony.perard@citrix.com Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit On Fri, Jul 19, 2019 at 03:41:52PM +0100, Andrew Cooper wrote: > On 19/07/2019 15:33, Laszlo Ersek wrote: > > On 07/19/19 12:20, Anthony PERARD wrote: > >> On Fri, Jul 05, 2019 at 02:57:06PM +0100, Andrew Cooper wrote: > >>> On 04/07/2019 15:42, Anthony PERARD wrote: > >>>> diff --git a/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm > >>>> new file mode 100644 > >>>> index 0000000000..958195bc5e > >>>> --- /dev/null > >>>> +++ b/OvmfPkg/XenResetVector/Ia16/ResetVectorVtf0.asm > >>>> +vtfSignature: > >>>> + DB 'V', 'T', 'F', 0 > >>>> + > >>>> +ALIGN 16 > >>>> + > >>>> +resetVector: > >>>> +; > >>>> +; Reset Vector > >>>> +; > >>>> +; This is where the processor will begin execution > >>>> +; > >>>> + nop > >>>> + nop > >>> Why two nops? > >> I don't know, this is existing code that I duplicated to allow adding a > >> new entry point. (I wanted to use --find-copies-harder when sending the > >> patch, but forgot this time. > > Not a big problem; while reviewing v3, I did such comparisons myself, in > > my local clone. Feel free to skip "--find-copies-harder" when posting v4 > > too; I think there isn't much churn going on in parallel right now. > > > > However, a new request for v4: please make sure that the new modules / > > paths introduced by this patch set are covered in Maintainers.txt. Will do. > >> This part of the chunk would not be there.) > > Regarding the NOPs: all I can tell you is that they originate from > > commit 8332983e2e33 ("UefiCpuPkg: Replace the un-necessary WBINVD > > instruction at the reset vector with two NOPs in VTF0.", 2011-08-04). > > > > Whether that change made sense back then, let alone if it makes sense > > now: no clue. > > Dropping wbinvd makes sense, because when virtualised, the caches (and > paging for that matter) are always up and running correctly.  Its an > unnecessary vmexit for something which the hypervisor will nop out anyway. > > Leaving two nops behind makes no sense at all. I'll remove the nops. Thanks, -- Anthony PERARD