From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail02.groups.io (mail02.groups.io [66.175.222.108]) by spool.mail.gandi.net (Postfix) with ESMTPS id 5A9DC940E78 for ; Thu, 22 Feb 2024 02:17:11 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=3MgsyDwp3a7IyJcEDC7EHlm5QqLzA9kY8s9QsmslOFc=; c=relaxed/simple; d=groups.io; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References:In-Reply-To:Precedence:List-Subscribe:List-Help:Sender:List-Id:Mailing-List:Delivered-To:Reply-To:List-Unsubscribe-Post:List-Unsubscribe:Content-Language:Content-Type:Content-Transfer-Encoding; s=20140610; t=1708568229; v=1; b=M+2HLgNtm7OFfddOKEgAbxbnZYfBjH14UvZapvH5z/ASfpNfiNN6IH46AzMEGVZzXeQgYDf3 cosut3oaOlP69KXwZkr0f/nAPvyU/6RAF7xjmLb/RtCi78gThan2JXwgFYSxN9Mx3gw9Z9Tp4zT Y7n9iEA7sBNZANmea2VYRRKs= X-Received: by 127.0.0.2 with SMTP id BXaaYY7687511xvpsS3YtbeR; Wed, 21 Feb 2024 18:17:09 -0800 X-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.web10.4305.1708568229298379474 for ; Wed, 21 Feb 2024 18:17:09 -0800 X-Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-638-iyRZl8auP_OqSHsO9fy9sA-1; Wed, 21 Feb 2024 21:17:05 -0500 X-MC-Unique: iyRZl8auP_OqSHsO9fy9sA-1 X-Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0BF691C05AEE; Thu, 22 Feb 2024 02:17:05 +0000 (UTC) X-Received: from [10.39.192.46] (unknown [10.39.192.46]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 0C8DB200B436; Thu, 22 Feb 2024 02:17:03 +0000 (UTC) Message-ID: Date: Thu, 22 Feb 2024 03:17:02 +0100 MIME-Version: 1.0 Subject: Re: [edk2-devel] [PATCH v2 5/5] UefiCpuPkg/MpInitLib: Add support for multiple HOBs to SaveCpuMpData() From: "Laszlo Ersek" To: devel@edk2.groups.io, kraxel@redhat.com, ray.ni@intel.com Cc: Oliver Steffen , "Kumar, Rahul R" References: <20240220174939.1288689-1-kraxel@redhat.com> <20240220174939.1288689-6-kraxel@redhat.com> <18d3de31-c7d9-f1d6-77f7-e147679349b1@redhat.com> In-Reply-To: <18d3de31-c7d9-f1d6-77f7-e147679349b1@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.4 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Precedence: Bulk List-Subscribe: List-Help: Sender: devel@edk2.groups.io List-Id: Mailing-List: list devel@edk2.groups.io; contact devel+owner@edk2.groups.io Reply-To: devel@edk2.groups.io,lersek@redhat.com List-Unsubscribe-Post: List-Unsubscribe=One-Click List-Unsubscribe: X-Gm-Message-State: 14V733nWVivnoUAUuckUtDurx7686176AA= Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=M+2HLgNt; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=redhat.com (policy=none); spf=pass (spool.mail.gandi.net: domain of bounce@groups.io designates 66.175.222.108 as permitted sender) smtp.mailfrom=bounce@groups.io On 2/22/24 02:49, Laszlo Ersek wrote: > (commenting once more, to explain the actual reason:) > > On 2/21/24 11:24, Gerd Hoffmann wrote: >> On Wed, Feb 21, 2024 at 03:48:25AM +0000, Ni, Ray wrote: >>>> >>>> + MaxCpusPerHob = (MAX_UINT16 - sizeof (EFI_HOB_GUID_TYPE) - sizeof >>>> (MP_HAND_OFF)) / sizeof (PROCESSOR_HAND_OFF); >>> >>> Above formula assumes the maximum HOB length could be 0xFFFF. >> >> Which is IMHO correct. > > It is not correct: > >> >>> But actually the maximum HOB length could be only 0xFFF8 because >>> PeiCore::PeiCreateHob() contains following logic: >>> >>> if (0x10000 - Length <= 0x7) { >>> return EFI_INVALID_PARAMETER; >>> } >> >> That Length is the *data* size, the HOB header is not included. sorry, I meant to insert here: no; "Length" at this location does include everything, except the padding. The BuildGuidHob() library function takes a data length, and calculates the total HOB length, by adding 24 bytes, for the EFI_HOB_GUID_TYPE header. InternalPeiCreateHob() (also in "MdePkg/Library/PeiHobLib/HobLib.c") already takes the total HOB length, and passes it on to the CreateHob() PEI service -- which Ray quotes above. The total HOB length cannot exceed 0xFFF8 (due to the rounding up, for Itanium's sake), so the GUID HOB data length cannot exceed (0xFFF8-sizeof(EFI_HOB_GUID_TYPE)). Laszlo >> >> The "- sizeof (EFI_HOB_GUID_TYPE)" in the formula above accounts the >> space needed for HOB header and GUID. > > Yes, but the problem is not that we need the extra space for > EFI_HOB_GUID_TYPE (24 bytes) -- we need the extra space for padding / > alignment. > > This is what the PI spec says (v1.8, section "III-4.5.2 HOB Construction > Rules"): > > HOB construction must obey the following rules: > > [...] > > 4. All HOBs must be multiples of 8 bytes in length. This requirement > meets the alignment restrictions of the Itanium® processor family. > > [...] > > And if your total *desired* HOB length exceeds 0xFFF8 (i.e., it falls in > [0xFFF9..0xFFFF]), then the required upwards rounding produces 0x1_0000. > But that rounded-up value cannot be expressed in > "EFI_HOB_GENERIC_HEADER.HobLength" -- a UINT16 field. > > In short, you've got Itanium to thank for this. :) > > Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#115772): https://edk2.groups.io/g/devel/message/115772 Mute This Topic: https://groups.io/mt/104472313/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=-=-=-=-=-=-=-=-=-=-=-