linux-kernel - Re: [PATCH v5 06/16] x86/tdx: Make DMA pages shared

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Message-ID: <930ec8e0-669d-8501-af66-38e4cab60a1f@linux.intel.com>
Date:   Wed, 20 Oct 2021 10:26:29 -0700
From:   Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Richard Henderson <rth@...ddle.net>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        James E J Bottomley <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        "David S . Miller" <davem@...emloft.net>,
        Arnd Bergmann <arnd@...db.de>,
        Jonathan Corbet <corbet@....net>,
        "Michael S . Tsirkin" <mst@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter H Anvin <hpa@...or.com>, Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Kuppuswamy Sathyanarayanan <knsathya@...nel.org>,
        x86@...nel.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-alpha@...r.kernel.org,
        linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-doc@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v5 06/16] x86/tdx: Make DMA pages shared



On 10/20/21 10:22 AM, Tom Lendacky wrote:
>>
>> For non TDX case, in CC_ATTR_HOST_MEM_ENCRYPT, we should still call
>> amd_force_dma_unencrypted() right?
> 
> What I'm saying is that you wouldn't have amd_force_dma_unencrypted(). I 
> think the whole force_dma_unencrypted() can exist as-is in a different 
> file, whether that's cc_platform.c or mem_encrypt_common.c.
> 
> It will return true for an SEV or TDX guest, true for an SME host based 
> on the DMA mask or else false. That should work just fine for TDX.

Got it. Thanks for clarifying it.

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer