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Date:   Mon, 28 Feb 2022 19:20:56 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
To:     Josh Poimboeuf <jpoimboe@redhat.com>
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@intel.com, luto@kernel.org, peterz@infradead.org,
        sathyanarayanan.kuppuswamy@linux.intel.com, aarcange@redhat.com,
        ak@linux.intel.com, dan.j.williams@intel.com, david@redhat.com,
        hpa@zytor.com, jgross@suse.com, jmattson@google.com,
        joro@8bytes.org, knsathya@kernel.org, pbonzini@redhat.com,
        sdeep@vmware.com, seanjc@google.com, tony.luck@intel.com,
        vkuznets@redhat.com, wanpengli@tencent.com,
        thomas.lendacky@amd.com, brijesh.singh@amd.com, x86@kernel.org,
        linux-kernel@vger.kernel.org, David Rientjes <rientjes@google.com>
Subject: Re: [PATCHv4 01/30] x86/mm: Fix warning on build with
 X86_MEM_ENCRYPT=y
Message-ID: <20220228162056.gul22bjr4w6zjslq@black.fi.intel.com>
References: <20220224155630.52734-1-kirill.shutemov@linux.intel.com>
 <20220224155630.52734-2-kirill.shutemov@linux.intel.com>
 <20220227220130.23yjme7jucxo266l@treble>
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On Sun, Feb 27, 2022 at 02:01:30PM -0800, Josh Poimboeuf wrote:
> 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@linux.intel.com>
> > Fixes: 20f07a044a76 ("x86/sev: Move common memory encryption code to mem_encrypt.c")
> > Acked-by: David Rientjes <rientjes@google.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.

maintainer-tip.rst seems disagree with you:

   A Fixes tag should be added even for changes which do not need to be
   backported to stable kernels, i.e. when addressing a recently introduced
   issue which only affects tip or the current head of mainline.

I will leave it as is.

-- 
 Kirill A. Shutemov