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Subject: Re: [RFC v2 26/32] x86/mm: Move force_dma_unencrypted() to common
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To:     Sean Christopherson <seanjc@google.com>,
        Dave Hansen <dave.hansen@intel.com>
Cc:     Andi Kleen <ak@linux.intel.com>,
        "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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From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@linux.intel.com>
Message-ID: <37da11b3-0313-982d-5a2b-af592db6f9e8@linux.intel.com>
Date:   Mon, 17 May 2021 15:32:01 -0700
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On 5/17/21 11:37 AM, Sean Christopherson wrote:
>> 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.
> Ya, exactly.  Ideally, generic code shouldn't have to differentiate between SEV,
> SEV-ES, SEV-SNP, TDX, etc..., a vanilla "bool is_protected_guest(void)" should
> suffice.  Under the hood, x86's implementation for is_protected_guest() can be
> boot_cpu_has() checks (if we want).

What about the use case of protected_guest_has(flag)? Do you want to call it with
with X86_FEATURE_* flags outside arch/x86 code ?


-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer