From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B5041C43334 for ; Fri, 24 Jun 2022 18:05:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3C0E48E025C; Fri, 24 Jun 2022 14:05:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 370C38E0244; Fri, 24 Jun 2022 14:05:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23A158E025C; Fri, 24 Jun 2022 14:05:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 15C9C8E0244 for ; Fri, 24 Jun 2022 14:05:51 -0400 (EDT) Received: from smtpin11.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id E5F1E6097A for ; Fri, 24 Jun 2022 18:05:50 +0000 (UTC) X-FDA: 79613907660.11.0B8A4AC Received: from mail-lf1-f54.google.com (mail-lf1-f54.google.com [209.85.167.54]) by imf20.hostedemail.com (Postfix) with ESMTP id 79E501C0030 for ; Fri, 24 Jun 2022 18:05:50 +0000 (UTC) Received: by mail-lf1-f54.google.com with SMTP id z21so5721967lfb.12 for ; Fri, 24 Jun 2022 11:05:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=amHl1LwfBMa5KDjXqZHtC9+AbtdwaHnaESVYa8U2byA=; b=H3sKSrgk4dk9/Hswlf5QYJecr2rGepFCacSgMNlU5bXC/icuTUS4zFuhsYf8UFjjCl 7/uIbmhnQiOjSjUOFuIuBSts3AMRMzgWX3yVxFfx3qaF3if0Z9wLFrEPzXxT6ROgcn0l gaMeTc9x99Xx1Wx+cZ9YaO54F8L5PBMeuY0cPogpowiUHI3o8nS6Q72kFDv3YskTyoW6 ei3dsCuqyqMjnfD+uwcmzgj2yWMVDCsAxOUG/UsCydZsHdLxr7Pr0cfTobtEFm6CV0JK gWUVtOIWoX1tS164asj2tha1HSnVTDEw1BECD2k7dNu62R2ysxNEmQ41MUY+c/3LHM49 C0eQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=amHl1LwfBMa5KDjXqZHtC9+AbtdwaHnaESVYa8U2byA=; b=E/0JRWtUpf1pJaVyTLXT5bqVzOCHO5BFbUnBI2TR6f8yI2SBcJhvLS12FcGjrInBFw BqaEth6GeWoyU5aKZ1i0rRdZzBRZP9ETica2djrrP3NikDYLKJc+dtKUJTuOEUdCNhTu B12GozHIBuRUV2oAEn2gh2OcUQUa8gbBLtgmMCjN60awS7b9DnCmjYQCcKyFAauttWYs ziLRIB5xNq1DOGIp3UwlbK5c32uM39Bs4pQQFgtxXr8op7u7EzCo9qedmdXKFD+bNW4a yHitkeYPBcPelczLSwnAR61u8bdlxck2pF+71+Ib2CP3a2cB1D7vRZ6VJeq5JaNNzYLo wCHw== X-Gm-Message-State: AJIora83rYH3D313edt6A9rcVRRtExSGe610QSK/pPNuTws/iJCPHQ+I 7lYAr9FElxyu4jnh4nlkCqtJqN1r2ksVw+Iz4xgSfA== X-Google-Smtp-Source: AGRyM1tQtvJ18kWM/znxc03I5G944GYbAvbUIXDCbDeZWIxGFl9h3QrIwEsXgHtgvQ25f40ZDrIp4mN4pcgMt5IV8i0= X-Received: by 2002:a05:6512:a94:b0:47f:6621:cf2a with SMTP id m20-20020a0565120a9400b0047f6621cf2amr73823lfu.193.1656093948467; Fri, 24 Jun 2022 11:05:48 -0700 (PDT) MIME-Version: 1.0 References: <20220614120231.48165-1-kirill.shutemov@linux.intel.com> <20220624174057.72dwo7v36lokmoub@amd.com> In-Reply-To: <20220624174057.72dwo7v36lokmoub@amd.com> From: Peter Gonda Date: Fri, 24 Jun 2022 12:05:36 -0600 Message-ID: Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory To: Michael Roth Cc: "Kirill A. Shutemov" , Borislav Petkov , Andy Lutomirski , Sean Christopherson , Andrew Morton , Joerg Roedel , Ard Biesheuvel , Andi Kleen , Kuppuswamy Sathyanarayanan , David Rientjes , Vlastimil Babka , Tom Lendacky , Thomas Gleixner , Peter Zijlstra , Paolo Bonzini , Ingo Molnar , Varad Gautam , Dario Faggioli , Dave Hansen , Mike Rapoport , David Hildenbrand , Marcelo , tim.gardner@canonical.com, Khalid ElMously , philip.cox@canonical.com, "the arch/x86 maintainers" , linux-mm@kvack.org, linux-coco@lists.linux.dev, linux-efi@vger.kernel.org, LKML Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=H3sKSrgk; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf20.hostedemail.com: domain of pgonda@google.com designates 209.85.167.54 as permitted sender) smtp.mailfrom=pgonda@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1656093950; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=amHl1LwfBMa5KDjXqZHtC9+AbtdwaHnaESVYa8U2byA=; b=RTwb4xLbbrGM5Q2Qu4IPaTETFLF7VAa6fYX0IHzJqdjfo7A97XtmSIeYrM0WT40VuAsn43 4lNu8sj7DleRFBV2KPzq9KBxTHUGTFYPFgQwXabxNashWUzj21kKnVOY3x9rx07Z0OkdHh 3c5yt63rSYUIk6iv0Zd3A/h6Rp77aFU= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1656093950; a=rsa-sha256; cv=none; b=zrmAwKQMobZlE2v68MafpJHMwg7SmRNL9W2ywIk4OWdjEHruI74x0kJValPdki2WTPre0A xKUcwi5PFpcUM2xwFeg65H3jd6HeaJDfXfd7k0YhKWB2ot0SLvzIS6toWSMltloM7c/iur LMudg2YGNholFmzSS4yRjQ7VG1CevS8= X-Stat-Signature: kjxkoopwemw3sd73tfs3ytzist35mgn7 X-Rspamd-Queue-Id: 79E501C0030 X-Rspam-User: Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=H3sKSrgk; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf20.hostedemail.com: domain of pgonda@google.com designates 209.85.167.54 as permitted sender) smtp.mailfrom=pgonda@google.com X-Rspamd-Server: rspam12 X-HE-Tag: 1656093950-997074 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Jun 24, 2022 at 11:41 AM Michael Roth wrote: > > On Fri, Jun 24, 2022 at 10:37:10AM -0600, Peter Gonda wrote: > > On Tue, Jun 14, 2022 at 6:03 AM Kirill A. Shutemov > > wrote: > > > > > > UEFI Specification version 2.9 introduces the concept of memory > > > acceptance: some Virtual Machine platforms, such as Intel TDX or AMD > > > SEV-SNP, requiring memory to be accepted before it can be used by the > > > guest. Accepting happens via a protocol specific for the Virtual > > > Machine platform. > > > > > > Accepting memory is costly and it makes VMM allocate memory for the > > > accepted guest physical address range. It's better to postpone memory > > > acceptance until memory is needed. It lowers boot time and reduces > > > memory overhead. > > > > > > The kernel needs to know what memory has been accepted. Firmware > > > communicates this information via memory map: a new memory type -- > > > EFI_UNACCEPTED_MEMORY -- indicates such memory. > > > > > > Range-based tracking works fine for firmware, but it gets bulky for > > > the kernel: e820 has to be modified on every page acceptance. It lead= s > > > to table fragmentation, but there's a limited number of entries in th= e > > > e820 table > > > > > > Another option is to mark such memory as usable in e820 and track if = the > > > range has been accepted in a bitmap. One bit in the bitmap represents > > > 2MiB in the address space: one 4k page is enough to track 64GiB or > > > physical address space. > > > > > > In the worst-case scenario -- a huge hole in the middle of the > > > address space -- It needs 256MiB to handle 4PiB of the address > > > space. > > > > > > Any unaccepted memory that is not aligned to 2M gets accepted upfront= . > > > > > > The approach lowers boot time substantially. Boot to shell is ~2.5x > > > faster for 4G TDX VM and ~4x faster for 64G. > > > > > > TDX-specific code isolated from the core of unaccepted memory support= . It > > > supposed to help to plug-in different implementation of unaccepted me= mory > > > such as SEV-SNP. > > > > > > The tree can be found here: > > > > > > https://nam11.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Fg= ithub.com%2Fintel%2Ftdx.git&data=3D05%7C01%7Cmichael.roth%40amd.com%7C7= 3bacba017c84291482a08da55ffd481%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%= 7C637916854542432349%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2= luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=3DP%2FUJOL30= 5xo85NLXGxGouQVGHgzLJpmBdNyZ7Re5%2FB0%3D&reserved=3D0 guest-unaccepted-= memory > > > > Hi Kirill, > > > > I have a couple questions about this feature mainly about how cloud > > customers can use this, I assume since this is a confidential compute > > feature a large number of the users of these patches will be cloud > > customers using TDX and SNP. One issue I see with these patches is how > > do we as a cloud provider know whether a customer's linux image > > supports this feature, if the image doesn't have these patches UEFI > > needs to fully validate the memory, if the image does we can use this > > new protocol. In GCE we supply our VMs with a version of the EDK2 FW > > and the customer doesn't input into which UEFI we run, as far as I can > > tell from the Azure SNP VM documentation it seems very similar. We > > need to somehow tell our UEFI in the VM what to do based on the image. > > The current way I can see to solve this issue would be to have our > > customers give us metadata about their VM's image but this seems kinda > > burdensome on our customers (I assume we'll have more features which > > both UEFI and kernel need to both support inorder to be turned on like > > this one) and error-prone, if a customer incorrectly labels their > > > image it may fail to boot.. Has there been any discussion about how to > > solve this? My naive thoughts were what if UEFI and Kernel had some > > sort of feature negotiation. Maybe that could happen via an extension > > to exit boot services or a UEFI runtime driver, I'm not sure what's > > best here just some ideas. > > Not sure if you've seen this thread or not, but there's also been some > discussion around this in the context of the UEFI support: > > https://patchew.org/EDK2/cover.1654420875.git.min.m.xu@intel.com/cce5ea= 2aaaeddd9ce9df6fa7ac1ef52976c5c7e6.1654420876.git.min.m.xu@intel.com/#20220= 608061805.vvsjiqt55rqnl3fw@sirius.home.kraxel.org > > 2 things being discussed there really, which I think roughly boil down > to: > > 1) how to configure OVMF to enable/disable lazy acceptance > - compile time option most likely: accept-all/accept-minimum/accept-1= GB > > 2) how to introduce an automatic mode in the future where OVMF does the > right thing based on what the guest supports. Gerd floated the idea o= f > tying it to ExitBootServices as well, but not sure there's a solid > plan on what to do here yet. > > If that's accurate, it seems like the only 'safe' option is to disable it= via > #1 (accept-all), and then when #2 comes along, compile OVMF to just Do Th= e > Right Thing. > > Users who know their VMs implement lazy acceptance can force it on via > accept-all OVMF compile option. Thanks for this Mike! I will bring this to the EDK2 community. The issue for us is our users use a GCE built EDK2 not their own compiled version so they don't have the choice. Reading the Azure docs it seems the same for them, and for AWS so I don't know how often customers actually get to bring their own firmware. > > -Mike