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 75C6D9413FC for ; Mon, 5 Feb 2024 08:14:33 +0000 (UTC) DKIM-Signature: a=rsa-sha256; bh=dWkSSmel8IqkwDZdHAnb3gfS5d3bIdpP4XeyIsERbBw=; c=relaxed/simple; d=groups.io; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: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=1707120871; v=1; b=X7m+QgVAmjCy5B0XD8B7MAfhjKGyT5+kjN6VG2l9HjvRASqXON5bpYjELQkD5b/5wJwOW48X Mjb8x+02+mywYYkCaz1GxN6vrb9nyJKHEQm2NF61b/Hw3LyNqjuU4zmZmNxoiPJ18KBIg2jT+yI sB1pGOWLL1KnLtbI0UYoLLR4= X-Received: by 127.0.0.2 with SMTP id YJuPYY7687511x2oeUD3AzN4; Mon, 05 Feb 2024 00:14:31 -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.web11.58310.1707120870747325284 for ; Mon, 05 Feb 2024 00:14:31 -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-564-cIsD5jtmPFumhNObcM_Wtw-1; Mon, 05 Feb 2024 03:14:26 -0500 X-MC-Unique: cIsD5jtmPFumhNObcM_Wtw-1 X-Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (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 5A2233C000B5; Mon, 5 Feb 2024 08:14:26 +0000 (UTC) X-Received: from [10.39.192.216] (unknown [10.39.192.216]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 66086492BC6; Mon, 5 Feb 2024 08:14:25 +0000 (UTC) Message-ID: <6a5ece37-2164-e207-7779-6a1258c7445e@redhat.com> Date: Mon, 5 Feb 2024 09:14:24 +0100 MIME-Version: 1.0 Subject: Re: [edk2-devel] [PATCH v2 3/4] OvmfPkg/PlatformPei: rewrite page table calculation To: devel@edk2.groups.io, kraxel@redhat.com Cc: Jiewen Yao , Oliver Steffen , Ard Biesheuvel References: <20240202104720.1275308-1-kraxel@redhat.com> <20240202104720.1275308-4-kraxel@redhat.com> From: "Laszlo Ersek" In-Reply-To: <20240202104720.1275308-4-kraxel@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 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: V3XPPd0gtpkW9FORMgBAAUPex7686176AA= Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-GND-Status: LEGIT Authentication-Results: spool.mail.gandi.net; dkim=pass header.d=groups.io header.s=20140610 header.b=X7m+QgVA; 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 2/2/24 11:47, Gerd Hoffmann wrote: > Consider 5-level paging. Simplify calculation to make it easier > to understand. Add some comments, improve ASSERTs. >=20 > Signed-off-by: Gerd Hoffmann > --- > OvmfPkg/PlatformPei/MemDetect.c | 56 ++++++++++++++++++++------------- > 1 file changed, 35 insertions(+), 21 deletions(-) >=20 > diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDet= ect.c > index 83f1c1d02a26..48ad0b83a55e 100644 > --- a/OvmfPkg/PlatformPei/MemDetect.c > +++ b/OvmfPkg/PlatformPei/MemDetect.c > @@ -184,9 +184,12 @@ GetPeiMemoryCap ( > BOOLEAN Page1GSupport; > UINT32 RegEax; > UINT32 RegEdx; > - UINT32 Pml4Entries; > - UINT32 PdpEntries; > - UINTN TotalPages; > + UINT64 MaxAddr; > + UINT32 Level5Pages; > + UINT32 Level4Pages; > + UINT32 Level3Pages; > + UINT32 Level2Pages; > + UINT32 TotalPages; > UINT64 ApStacks; > UINT64 MemoryCap; > =20 > @@ -203,8 +206,7 @@ GetPeiMemoryCap ( > // > // Dependent on physical address width, PEI memory allocations can be > // dominated by the page tables built for 64-bit DXE. So we key the ca= p off > - // of those. The code below is based on CreateIdentityMappingPageTable= s() in > - // "MdeModulePkg/Core/DxeIplPeim/X64/VirtualMemory.c". > + // of those. > // > Page1GSupport =3D FALSE; > if (PcdGetBool (PcdUse1GPageTable)) { > @@ -217,25 +219,37 @@ GetPeiMemoryCap ( > } > } > =20 > - if (PlatformInfoHob->PhysMemAddressWidth <=3D 39) { > - Pml4Entries =3D 1; > - PdpEntries =3D 1 << (PlatformInfoHob->PhysMemAddressWidth - 30); > - ASSERT (PdpEntries <=3D 0x200); > + // > + // - A 4KB page accommodates the least significant 12 bits of the > + // virtual address. > + // - A page table entry at any level consumes 8 bytes, so a 4KB page > + // table page (at any level) contains 512 entries, and > + // accommodates 9 bits of the virtual address. > + // - we minimally cover the phys address space with 2MB pages, so > + // level 1 never exists. > + // - If 1G paging is available, then level 2 doesn't exist either. > + // - Start with level 2, where a page table page accommodates > + // 9 + 9 + 12 =3D 30 bits of the virtual address (and covers 1GB of > + // physical address space). > + // > + > + MaxAddr =3D LShiftU64 (1, PlatformInfoHob->PhysMemAddressWidth); > + Level2Pages =3D (UINT32)RShiftU64 (MaxAddr, 30); > + Level3Pages =3D MAX (Level2Pages >> 9, 1); (1) The MAX() macro in "MdePkg/Include/Base.h" is documented like this: /** Return the maximum of two operands. This macro returns the maximum of two operand specified by a and b. Both a and b must be the same numerical types, signed or unsigned. @param a The first operand with any numerical type. @param b The second operand. Can be any numerical type as long a= s is the same type as a. @return Maximum of two operands. **/ This does not hold to the above expression. (Level2Pages >> 9) is a UINT32,= but "1" is an INT32. Please use "1u". (Note that the replacement text of the macro, namely (((a) > (b)) ? (a) : (= b)), would work fine as-is, but we still should not break the documented in= terface.) > + Level4Pages =3D MAX (Level3Pages >> 9, 1); (2) Same comment as above, plus another one: (3) I'm slightly disturbed by the fact that here we don't shift the origina= l MaxAddr by 48 bits, but Level3Pages by 9 bits. Namely, if Level3Pages was= set to 1 by the MAX (i.e., because the >> 39 resulted in zero), then the i= nput of *this* bit shift is nonsensical. It's a happenstance that 1 >> 9 is= zero too, for Level4Pages, and we're just exploiting that practical result= here. I think this is semantically unclean, especially without a comment, but I d= on't want to insist anymore. > + Level5Pages =3D 1; > + > + if (Page1GSupport) { > + Level2Pages =3D 0; > + TotalPages =3D Level5Pages + Level4Pages + Level3Pages; > + ASSERT (TotalPages <=3D 0x40201); > } else { > - if (PlatformInfoHob->PhysMemAddressWidth > 48) { > - Pml4Entries =3D 0x200; > - } else { > - Pml4Entries =3D 1 << (PlatformInfoHob->PhysMemAddressWidth - 39); > - } > - > - ASSERT (Pml4Entries <=3D 0x200); > - PdpEntries =3D 512; > + TotalPages =3D Level5Pages + Level4Pages + Level3Pages + Level2Pages= ; > + // PlatformAddressWidthFromCpuid() caps at 40 phys bits without 1G p= ages. > + ASSERT (PlatformInfoHob->PhysMemAddressWidth <=3D 40); > + ASSERT (TotalPages <=3D 0x404); > } > =20 > - TotalPages =3D Page1GSupport ? Pml4Entries + 1 : > - (PdpEntries + 1) * Pml4Entries + 1; > - ASSERT (TotalPages <=3D 0x40201); > - > // > // With 32k stacks and 4096 vcpus this lands at 128 MB (far away > // from MAX_UINT32). With (1) and (2) updated (feel free to ignore (3)): Reviewed-by: Laszlo Ersek -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#115104): https://edk2.groups.io/g/devel/message/115104 Mute This Topic: https://groups.io/mt/104117101/7686176 Group Owner: devel+owner@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [rebecca@openfw.io] -=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-=3D-