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Subject: Re: [RFC v2 26/32] x86/mm: Move force_dma_unencrypted() to common
 code
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        Sean Christopherson <seanjc@google.com>,
        Andi Kleen <ak@linux.intel.com>
Cc:     "Kirill A. Shutemov" <kirill@shutemov.name>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Kirill Shutemov <kirill.shutemov@linux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@kernel.org>,
        Raj Ashok <ashok.raj@intel.com>, linux-kernel@vger.kernel.org
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Message-ID: <5cc06488-09fe-17b5-077b-02c4ba9ca198@intel.com>
Date:   Mon, 17 May 2021 11:33:29 -0700
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On 5/17/21 11:27 AM, Kuppuswamy, Sathyanarayanan wrote:
> On 5/17/21 11:16 AM, Sean Christopherson wrote:
>> What generic code needs access to SEV vs. TDX? 
>> force_dma_unencrypted() is called from generic code, but its
>> implementation is x86 specific.
> 
> When the hardening the drivers for TDX usage, we will have
> requirement to check for is_protected_guest() to add code specific to
> protected guests. Since this will be outside arch/x86, we need common
> framework for it.

Just remember, a "common framework" doesn't mean that it can't be backed
by extremely arch-specific mechanisms.

For instance, there's a lot of pkey-specific code in mm/mprotect.c.  It
still gets optimized away on x86 with all the goodness of X86_FEATUREs.