From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124])
 by mx.groups.io with SMTP id smtpd.web11.11253.1674032735794925710
 for <devel@edk2.groups.io>;
 Wed, 18 Jan 2023 01:05:35 -0800
Authentication-Results: mx.groups.io;
 dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=caDybc6a;
 spf=pass (domain: redhat.com, ip: 170.10.133.124, mailfrom: kraxel@redhat.com)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com;
	s=mimecast20190719; t=1674032734;
	h=from:from:reply-to:subject:subject:date:date:message-id:message-id:
	 to:to:cc:cc:mime-version:mime-version:content-type:content-type:
	 in-reply-to:in-reply-to:references:references;
	bh=TwHecZhMIWZcZ05zyDMoBs+yv6byEdlpXrDu/ZxTxFc=;
	b=caDybc6aNtg0AWcZXQaicqmpDwEdSeWdZByCef+ZFEtCe5gMFygXZqdgvvq3i2vYkO0X/n
	FodrJQmBoyHdIZkwW0FKKwL64IisZfWO1TLoBf9avniXRPkbODiV05HYhlSc9XC0SLntmn
	mNfaxZXxMhD+OMgr7rIACB97vaZBSwQ=
Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com
 [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS
 (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
 us-mta-346-wzrO0kP5NAmC8S-v909sOg-1; Wed, 18 Jan 2023 04:05:31 -0500
X-MC-Unique: wzrO0kP5NAmC8S-v909sOg-1
Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5])
	(using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
	(No client certificate requested)
	by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F32B43C02545;
	Wed, 18 Jan 2023 09:05:30 +0000 (UTC)
Received: from sirius.home.kraxel.org (unknown [10.39.192.186])
	by smtp.corp.redhat.com (Postfix) with ESMTPS id BEAF153A0;
	Wed, 18 Jan 2023 09:05:30 +0000 (UTC)
Received: by sirius.home.kraxel.org (Postfix, from userid 1000)
	id 1FB4E1800091; Wed, 18 Jan 2023 10:05:29 +0100 (CET)
Date: Wed, 18 Jan 2023 10:05:29 +0100
From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Zhiguang Liu <zhiguang.liu@intel.com>
Cc: devel@edk2.groups.io, Rahul Kumar <rahul1.kumar@intel.com>,
	Star Zeng <star.zeng@intel.com>, Wu@sirius.home.kraxel.org,
	Jiaxin <jiaxin.wu@intel.com>, Ray Ni <ray.ni@intel.com>,
	Eric Dong <eric.dong@intel.com>
Subject: Re: [PATCH v2] UefiCpuPkg: Fix SMM code hangs when InitPaging
Message-ID: <20230118090529.bwp4qpluagrpk53x@sirius.home.kraxel.org>
References: <20230118012348.1195-1-zhiguang.liu@intel.com>
MIME-Version: 1.0
In-Reply-To: <20230118012348.1195-1-zhiguang.liu@intel.com>
X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5
X-Mimecast-Spam-Score: 0
X-Mimecast-Originator: redhat.com
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

On Wed, Jan 18, 2023 at 09:23:48AM +0800, Zhiguang Liu wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4246
> 
> In function InitPaging, NumberOfPml5Entries is calculated by below code
> NumberOfPml5Entries = (UINTN)LShiftU64 (1, SizeOfMemorySpace - 48);
> If the SizeOfMemorySpace is larger than 48, NumberOfPml5Entries will be
> larger than 1. However, this doesn't make sense if the hardware doesn't
> support 5 level page table.

... if 5-level paging is not used.

Hardware which does not support 5-level paging is limited to 48 anyway.

This still does not explain why this fixes code hangs.

take care,
  Gerd