linux-kernel - Re: [edk2-devel] [PATCH v2] x86/efi: Safely enable unaccepted memory in UEFI

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Message-ID: <20230118075140.6pyszln4ovi2htxk@sirius.home.kraxel.org>
Date:   Wed, 18 Jan 2023 08:51:40 +0100
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     devel@...2.groups.io, dionnaglaze@...gle.com
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Ard Biesheuvel <ardb@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
        x86@...nel.org, jiewen.yao@...el.com,
        "Min M. Xu" <min.m.xu@...el.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        Tom Lendacky <Thomas.Lendacky@....com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [edk2-devel] [PATCH v2] x86/efi: Safely enable unaccepted memory
 in UEFI

  Hi,

> To Gerd's point, removing "first in edk2, later in linux too" I think
> is backwards. We need all users of the protocol to agree that SEV-SNP
> and TDX strictly imply unaccepted memory support. Only then can we
> remove the protocol from EDK2.

Its not backwards.

edk2 dropping support first would result in break kernels without
support for unaccepted memory.  Which is why we wait until such
kernels are EOL.

Linux dropping support first would result in firmware accepting all
memory again.  So that isn't a good plan.  Thats why linux should
support the protocol a bit longer, while firmware versions which
expect negotiation happening are still in use.

take care,
  Gerd