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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E8E83C433EF for ; Fri, 24 Jun 2022 18:10:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230227AbiFXSKV (ORCPT ); Fri, 24 Jun 2022 14:10:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229480AbiFXSKU (ORCPT ); Fri, 24 Jun 2022 14:10:20 -0400 Received: from mail-lf1-x12b.google.com (mail-lf1-x12b.google.com [IPv6:2a00:1450:4864:20::12b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 073C349917 for ; Fri, 24 Jun 2022 11:10:19 -0700 (PDT) Received: by mail-lf1-x12b.google.com with SMTP id j21so5847326lfe.1 for ; Fri, 24 Jun 2022 11:10:18 -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; bh=hcN3XwIcZstb9s64xvU12TX0znKfRFFze9XJS0Qbx3c=; b=i388ivDFxBMUiQA7obdzFBcEsHyr2kSx+7nBsDjM07lnEAK/xcdqGFSUgzgUY2x5hz DEXehsWQSvUsV1Imkd8PWGjk00nG59mSuOc1lCrJJBgRYyUpD1jYVMip2WU88Ju3wXQC 9mMUu5erd6kQecAreB6NiXoTvzd9EWpyT6+hFRSjep65bDfex49cbaRobzUMHHHZ0Z84 eXEGdW5cEkmpQdRIfZYO6ikD12SduftZiMeR9H+O6dCGKcrFYtydLGHlB5ozixdcHDZo Sofuo2cji7slhGZ5UqgKB7QK/oxD3m0HAUfdsQDFVoue1IcLToG3jzOqCB83xL9+874H Tl3Q== 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; bh=hcN3XwIcZstb9s64xvU12TX0znKfRFFze9XJS0Qbx3c=; b=iO4Pqr4hS5BHra8UfcqKRuaOl5uWI4hWcBU2GCC44UlVznEDDvP0keHHB823li9pGj knGyN2WXrEv1O+qKG5emfh02wtqEELhmJ7WlzJjjtfuja2dDKWwJ+OreIN3SPxnXiDgD 6r20j3FTdZT9ltijCwBu8FUwemYkcmF1omk9UxGr0FhZe023rPBkOhOfXG97WBZbXH04 WGPPzpKY8lT2aawqYwOM1FuiiovK4Rhz65QGRo9EsgGupOK0lxz5Ray7GEKxPnijSXZN SPeiuDcqbQJybvIb9KbhWpgMeQgTs3ImjDgzYDhYdPR8qX4o5Khl8sE9VOsYlcUhfHCq 4NwQ== X-Gm-Message-State: AJIora8gsRmeuZ3pj++/F2UFHuwYaa8IPpUm4CVusGOunTDupowSgGGj tOu3YnaLz3prJFvIb3qp71sMk/CXVjabc0gh+d1XaQ== X-Google-Smtp-Source: AGRyM1tdkubN4l5CrWuEurB1wstbops6ikfefa6G3OKJ5WraDCy19/A/YOyuGj3Y9SbrsN+Oqd+6FVxlMDlWtFoEghE= X-Received: by 2002:ac2:5974:0:b0:47f:92db:4480 with SMTP id h20-20020ac25974000000b0047f92db4480mr59927lfp.685.1656094217190; Fri, 24 Jun 2022 11:10:17 -0700 (PDT) MIME-Version: 1.0 References: <20220614120231.48165-1-kirill.shutemov@linux.intel.com> <5af19000-4482-7eb9-f158-0a461891f087@intel.com> <1e7ad728-d796-c84d-b7ba-b96d8f9fcd0c@intel.com> In-Reply-To: <1e7ad728-d796-c84d-b7ba-b96d8f9fcd0c@intel.com> From: Peter Gonda Date: Fri, 24 Jun 2022 12:10:05 -0600 Message-ID: Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory To: Dave Hansen Cc: Marc Orr , "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 , 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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 24, 2022 at 11:47 AM Dave Hansen wrote: > > On 6/24/22 10:19, Marc Orr wrote: > >> Is this a matter of > >> > >> can boot from a guest firmware that doesn't pre-validate all the > >> guest memory? > >> > >> or > >> > >> can boot from a guest firmware that doesn't pre-validate all the > >> guest memory ... with access to all of that guest's RAM? > >> > >> In other words, are we talking about "fails to boot" or "can't see all > >> the RAM"? > > Ah... yeah, you're right, Dave -- I guess it's the latter. The guest > > won't have access to all of the memory that the customer is paying > > for. But that's still bad. If the customer buys a 96 GB VM and can > > only see 4GB because they're kernel doesn't have these patches they're > > going to be confused and frustrated. > > They'll at least be a _bit_ less angry and frustrated than if they were > staring at a blank screen. ;) But, yeah, I totally get the point. Ha! Well we do have that issue in some cases. If you try to run an SEV VM with an image that doesn't support SEV you will just get a blank serial screen. If we had something like this back then the FW could have surfaced a nice error to the user but that's history now. > > How big is the window going to be where we have guests that can have > unaccepted memory, but don't have acceptance support? For TDX, it's > looking like it'll probably _just_ be 5.19. Is TDX on 5.19 in shape > that cloud providers can deploy it? Or, is stuff like lack of > attestation a deal breaker? This is complicated because distros don't run upstream linux versions. If I understand correctly (I see some distro emails on here so please correct me) distros normally maintain forks which they backport things into. So I cannot answer this question. It is possible that a hypothetical distro backports only the SNP/TDX initial patches and doesn't take these for many releases. I am more familiar with SNP and it does have some attestation support in the first patch sets. Also I should have been more clear. I don't want to try and hold up this feature but instead discuss a future usability add-on feature. > >