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

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Message-ID: <943645b7-3974-bf05-073c-03ef4f889379@intel.com>
Date:   Thu, 13 May 2021 10:49:58 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        Raj Ashok <ashok.raj@...el.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 26/32] x86/mm: Move force_dma_unencrypted() to common
 code

On 5/13/21 9:40 AM, Kuppuswamy, Sathyanarayanan wrote:
> 
> +#define PROTECTED_GUEST_BITMAP_LEN    128
> +
> +/* Protected Guest vendor types */
> +#define GUEST_TYPE_TDX            (1)
> +#define GUEST_TYPE_SEV            (2)
> +
> +/* Protected Guest features */
> +#define MEMORY_ENCRYPTION        (20)

I was assuming we'd reuse the X86_FEATURE infrastructure somehow.  Is
there a good reason not to?

That gives us all the compile-time optimization (via
en/disabled-features.h) and static branches for "free".