linux-kernel - Re: [PATCHv4 01/30] x86/mm: Fix warning on build with X86_MEM

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Message-ID: <20220227220130.23yjme7jucxo266l@treble>
Date:   Sun, 27 Feb 2022 14:01:30 -0800
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org,
        sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, knsathya@...nel.org, pbonzini@...hat.com,
        sdeep@...are.com, seanjc@...gle.com, tony.luck@...el.com,
        vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org, David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCHv4 01/30] x86/mm: Fix warning on build with
 X86_MEM_ENCRYPT=y

On Thu, Feb 24, 2022 at 06:56:01PM +0300, Kirill A. Shutemov wrote:
> So far, AMD_MEM_ENCRYPT is the only user of X86_MEM_ENCRYPT. TDX will be
> the second. It will make mem_encrypt.c build without AMD_MEM_ENCRYPT,
> which triggers a warning:
> 
> arch/x86/mm/mem_encrypt.c:69:13: warning: no previous prototype for
> 	function 'mem_encrypt_init' [-Wmissing-prototypes]
> 
> Fix it by moving mem_encrypt_init() declaration outside of #ifdef
> CONFIG_AMD_MEM_ENCRYPT.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Fixes: 20f07a044a76 ("x86/sev: Move common memory encryption code to mem_encrypt.c")
> Acked-by: David Rientjes <rientjes@...gle.com>

The patch title, warning, and "Fixes" tag tend to give the impression
this is fixing a real user-visible bug.  But the bug is theoretical, as
it's not possible to enable X86_MEM_ENCRYPT without AMD_MEM_ENCRYPT,
until patch 27.

IMO it would be preferable to just squash this change with patch 27.

Having it as a separate patch is also fine, but it shouldn't be
described as a fix or use the Fixes tag.  It's more of a preparatory
patch.

-- 
Josh