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

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Message-ID: <d5fb2565-110e-17d1-ea00-35cf4d196f1e@linux.intel.com>
Date:   Mon, 17 May 2021 11:27:31 -0700
From:   "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        "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>,
        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 5/17/21 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.

Few examples are,
  * ACPI sleep driver uses WBINVD (when doing cache flushes). We want to skip it for
   TDX.
  * Forcing virtio to use dma API when running with untrusted host.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer