linux-kernel - Re: [PATCH Part1 RFC v3 20/22] x86/boot: Add Confidential Computing address to setup

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Message-ID: <20210624122655.cx3rugg5uvbeib5r@amd.com>
Date:   Thu, 24 Jun 2021 07:26:55 -0500
From:   Michael Roth <michael.roth@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     "Kuppuswamy, Sathyanarayanan" 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Brijesh Singh <brijesh.singh@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Sergio Lopez <slp@...hat.com>, Peter Gonda <pgonda@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>, tony.luck@...el.com,
        npmccallum@...hat.com
Subject: Re: [PATCH Part1 RFC v3 20/22] x86/boot: Add Confidential Computing
 address to setup_header

On Thu, Jun 24, 2021 at 09:27:41AM +0200, Borislav Petkov wrote:
> On Wed, Jun 23, 2021 at 10:19:11PM -0500, Michael Roth wrote:
> > One downside to this is we still need something in the boot protocol,
> > either via setup_data, or setup_header directly.
> 
> Huh, now I'm confused. You gave the acpi_rsdp_addr example and I thought
> that should be enough, that's why I suggested boot_params.

Well, that's enough for the boot/compressed->uncompressed parameter
passing, but would a bootloader be allowed to use that same approach to
pass in the CC blob (for things like non-EFI/containers)? I was under the
impression that for that case we'd still want something in
setup_header/setup_data for bootloaders to use, and that using boot_params
directly is more of a legacy/ad-hoc thing. Is that accurate?

> 
> Maybe you should point me to the code which does what you need so that I
> can get a better idea...
> 
> > Having it in setup_header avoids the need to also have to add a field
> > to boot_params for the boot/compressed->uncompressed passing, but
> > maybe that's not a good enough justification. Perhaps if the TDX folks
> > have similar needs though.
> 
> Yes, reportedly they do so I guess the solution should be
> vendor-agnostic. Let's see what they need first.

Ok, good to know.

> 
> Thx.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
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