Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220614120231.48165-1-kirill.shutemov@linux.intel.com>
 <CAMkAt6osbEGBFrgn=y1=x4mDHC1aL40BwaW0NdGHF8qmWd7ktA@mail.gmail.com>
 <20220627113019.3q62luiay7izhehr@black.fi.intel.com> <CAMj1kXHD5XBAS1aBjzg1RCeK6qgtanUSED_xyTZ0v1j+UShMKw@mail.gmail.com>
 <20220627122230.7eetepoufd5w3lxd@black.fi.intel.com> <CAMkAt6oJJaRM_dy=y2BP99VziPriVuA4jAmMc=G7njwJYKFgyg@mail.gmail.com>
 <CAMj1kXHpS2B9Q7AaQ1euGidZUEyR6gfi=e+t1J_Cr8bmK_9mTw@mail.gmail.com>
 <20220627223808.ihgy3epdx6ofll43@black.fi.intel.com> <CAMj1kXEdS9SzFZZ4WGH6sR0WDCOgYDZ3Geg6X2sqSnQ-CXXpZA@mail.gmail.com>
 <20220718172159.4vwjzrfthelovcty@black.fi.intel.com> <CAAH4kHYR+VkSJ5J8eWmeaEvstuRz_EuqVQqPfwmp5dhNGRyJwQ@mail.gmail.com>
 <CAAH4kHaHJo4NUb72tHeica4a34hq5u_QP6d6Vuzngf6EqTJ8Aw@mail.gmail.com>
In-Reply-To: <CAAH4kHaHJo4NUb72tHeica4a34hq5u_QP6d6Vuzngf6EqTJ8Aw@mail.gmail.com>
From:   Dionna Amalie Glaze <dionnaglaze@google.com>
Date:   Tue, 19 Jul 2022 11:29:32 -0700
Message-ID: <CAAH4kHaB2tL+sAn0NAciu5DQeX5hpNkDees=n=f83S=Ph9Y6tw@mail.gmail.com>
Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory
To:     "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     Ard Biesheuvel <ardb@kernel.org>, Peter Gonda <pgonda@google.com>,
        Borislav Petkov <bp@alien8.de>,
        Andy Lutomirski <luto@kernel.org>,
        Sean Christopherson <seanjc@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Joerg Roedel <jroedel@suse.de>,
        Andi Kleen <ak@linux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Ingo Molnar <mingo@redhat.com>,
        Varad Gautam <varad.gautam@suse.com>,
        Dario Faggioli <dfaggioli@suse.com>,
        Dave Hansen <dave.hansen@intel.com>,
        Mike Rapoport <rppt@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Marcelo Cerri <marcelo.cerri@canonical.com>,
        tim.gardner@canonical.com,
        Khalid ElMously <khalid.elmously@canonical.com>,
        philip.cox@canonical.com,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        linux-coco@lists.linux.dev, linux-efi <linux-efi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "Yao, Jiewen" <jiewen.yao@intel.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> > > I think we should make it obvious from a kernel image if it supports
> > > unaccepted memory (with UTS_VERSION or other way).
> > >
>
> Something I didn't address in my previous email: how would the UEFI
> know where the kernel is to parse this UTS_VERSION out when it's
> booting a bootloader before Linux gets booted?
>

How about instead of the limited resource of UTS_VERSION, we add a
SETUP_BOOT_FEATURES enum for setup_data in the boot header? That would
be easier to parse out and more extensible in the future.
https://www.kernel.org/doc/html/latest/x86/boot.html?highlight=boot

This can contain a bitmap of a number of features that we currently
need manual tagging for, such as SEV guest support, SEV-SNP guest
support, TDX guest support, and (CONFIG_UNACCEPTED_MEMORY, TDX) or
(CONFIG_UNACCEPTED_MEMORY, SEV-SNP).
The VMM, UEFI, or boot loader can read these from the images/kernels
and have the appropriate behavior.

-- 
-Dionna Glaze, PhD (she/her)