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

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Message-ID: <15568c80-c9a9-5602-d940-264af87bed98@amd.com>
Date:   Fri, 18 Jun 2021 08:57:12 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     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>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        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 6/18/2021 1:08 AM, Borislav Petkov wrote:
> On Wed, Jun 02, 2021 at 09:04:14AM -0500, Brijesh Singh wrote:
>> While launching the encrypted guests, the hypervisor may need to provide
>> some additional information that will used during the guest boot. In the
>> case of AMD SEV-SNP the information includes the address of the secrets
>> and CPUID pages. The secrets page contains information such as a VM to
>> PSP communication key and CPUID page contain PSP filtered CPUID values.
>>
>> When booting under the EFI based BIOS, the EFI configuration table
>> contains an entry for the confidential computing blob. In order to support
>> booting encrypted guests on non EFI VM, the hypervisor to pass these
>> additional information to the kernel with different method.
>>
>> For this purpose expand the struct setup_header to hold the physical
>> address of the confidential computing blob location. Being zero means it
>> isn't passed.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>  Documentation/x86/boot.rst            | 27 +++++++++++++++++++++++++++
>>  arch/x86/boot/header.S                |  7 ++++++-
>>  arch/x86/include/uapi/asm/bootparam.h |  1 +
>>  3 files changed, 34 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
>> index fc844913dece..9b32805617bb 100644
>> --- a/Documentation/x86/boot.rst
>> +++ b/Documentation/x86/boot.rst
>> @@ -75,6 +75,8 @@ Protocol 2.14	BURNT BY INCORRECT COMMIT
>>  		DO NOT USE!!! ASSUME SAME AS 2.13.
>>  
>>  Protocol 2.15	(Kernel 5.5) Added the kernel_info and kernel_info.setup_type_max.
>> +
>> +Protocol 2.16	(Kernel 5.14) Added the confidential computing blob address
>>  =============	============================================================
>>  
>>  .. note::
>> @@ -226,6 +228,7 @@ Offset/Size	Proto		Name			Meaning
>>  0260/4		2.10+		init_size		Linear memory required during initialization
>>  0264/4		2.11+		handover_offset		Offset of handover entry point
>>  0268/4		2.15+		kernel_info_offset	Offset of the kernel_info
>> +026C/4		2.16+		cc_blob_address	        Physical address of the confidential computing blob
> 
> Why is this a separate thing instead of being passed as setup_data?
> 

Don't have any strong reason to keep it separate, I can define a new type and use the
setup_data to pass this information.

-Brijesh