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Date:   Mon, 16 Jan 2023 13:22:45 -0800
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Subject: Re: [PATCH v2] x86/efi: Safely enable unaccepted memory in UEFI
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To:     Gerd Hoffmann <kraxel@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc:     Dionna Glaze <dionnaglaze@google.com>,
        linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
        x86@kernel.org, jiewen.yao@intel.com, devel@edk2.groups.io,
        Ard Biescheuvel <ardb@kernel.org>,
        "Min M. Xu" <min.m.xu@intel.org>,
        James Bottomley <jejb@linux.ibm.com>,
        Tom Lendacky <Thomas.Lendacky@amd.com>,
        Erdem Aktas <erdemaktas@google.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
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 <20230116105648.63hsxnmj2juwudmu@sirius.home.kraxel.org>
From:   Dave Hansen <dave.hansen@intel.com>
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On 1/16/23 02:56, Gerd Hoffmann wrote:
>> And we add this protocol to address very temporary problem: once
>> unaccepted memory support get upstream it is just a dead weight.
> Maybe, maybe not.  unaccepted memory support has a Kconfig switch after
> all.  If we figure in 3-5 years that all distros have enabled it anyway
> we can drop it again.  For the transition period it will surely be
> useful.

I agree with Kirill here.

Having unaccepted memory *AND* this firmware-driven feature really is
just implementing the same thing twice.

I'd much rather have the Kconfig option forced on for all guests that
*might* need unaccepted memory support than carry redundant implementations.

Also, _if_ we allow folks to turn the Kconfig off and get access to all
their memory, they might get used to that.  Removing this firmware
interface from the kernel in a few years could be viewed as a
regression.  Then, we'll be stuck with this forever.

In any case, the firmware side of things didn't seem like _that_ much
code.  So, I'm not protesting *that* strongly.  But, I also don't
believe for a second that this is going to be removed in 3-5 years.