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

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Date:   Tue, 31 Jan 2023 08:08:04 -0800
From:   Dionna Amalie Glaze <dionnaglaze@...gle.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     linux-kernel@...r.kernel.org, x86@...r.kernel.org,
        linux-efi@...r.kernel.org, "Min M. Xu" <min.m.xu@...el.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Tom Lendacky <Thomas.Lendacky@....com>,
        Jiewen Yao <jiewen.yao@...el.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v2, RESEND] x86/efi: Safely enable unaccepted memory in UEFI

> > +       efi_status_t status;
> > +
> > +       if (!IS_ENABLED(CONFIG_UNACCEPTED_MEMORY))
>
> Do we need to check for IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT) here as well?
>

Arguably no, since the firmware should only make the protocol
available when it determines that the protocol should be used. In our
case, that's just SEV-SNP. The firmware's TDX logic will not expose
this protocol.

This maintains flexibility for the rare case that the TDX go-to-market
schedule doesn't align with upstream's acceptance of unaccepted memory
support, but does accept the generic TDX support. Best not paint
ourselves into a corner.

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