linux-kernel - Re: [RFC v2 26/32] x86/mm: Move force_dma

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Message-ID: <bbcb688c-5aa0-eeb1-192a-45edaccc2f32@intel.com>
Date:   Mon, 10 May 2021 15:23:29 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>
Cc:     Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 26/32] x86/mm: Move force_dma_unencrypted() to common
 code

On 5/10/21 3:19 PM, Kuppuswamy, Sathyanarayanan wrote:
> On 5/7/21 2:54 PM, Dave Hansen wrote:
>> This doesn't seem much like common code to me.  It seems like 100% SEV
>> code.  Is this really where we want to move it?
> 
> Both SEV and TDX code has requirement to enable
> CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED and define force_dma_unencrypted()
> function.
> 
> force_dma_unencrypted() is modified by patch titled "x86/tdx: Make DMA
> pages shared" to add TDX guest specific support.
> 
> Since both SEV and TDX code uses it, its moved to common file.

That's not an excuse to have a bunch of AMD (or Intel) feature-specific
code in a file named "common".  I'd make an attempt to keep them
separate and then call into the two separate functions *from* the common
function.