linux-kernel - Re: [PATCH v12 29/46] x86/boot: Add Confidential Computing type to setup

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Message-ID: <496A3732-C91B-48B0-9DBB-126108174D93@zytor.com>
Date:   Sat, 16 Jul 2022 22:08:09 -0700
From:   "H. Peter Anvin" <hpa@...or.com>
To:     Brijesh Singh <brijesh.singh@....com>,
        Thomas Gleixner <tglx@...utronix.de>, 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
CC:     brijesh.singh@....com, Ingo Molnar <mingo@...hat.com>,
        Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.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>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v12 29/46] x86/boot: Add Confidential Computing type to setup_data

On April 7, 2022 7:57:22 AM PDT, Brijesh Singh <brijesh.singh@....com> wrote:
>
>
>On 4/6/22 16:19, Thomas Gleixner wrote:
>> On Mon, Mar 07 2022 at 15:33, Brijesh Singh wrote:
>>>   
>>> +/*
>>> + * AMD SEV Confidential computing blob structure. The structure is
>>> + * defined in OVMF UEFI firmware header:
>>> + * https://github.com/tianocore/edk2/blob/master/OvmfPkg/Include/Guid/ConfidentialComputingSevSnpBlob.h
>>> + */
>>> +#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
>>> +struct cc_blob_sev_info {
>>> +	u32 magic;
>>> +	u16 version;
>>> +	u16 reserved;
>>> +	u64 secrets_phys;
>>> +	u32 secrets_len;
>>> +	u32 rsvd1;
>>> +	u64 cpuid_phys;
>>> +	u32 cpuid_len;
>>> +	u32 rsvd2;
>>> +};
>> 
>> Shouldn't this be packed?
>> 
>
>Yep, to avoid any additional compiler alignment we should pack it.
>
>thanks

It shouldn't be *necessary*, any more than it is necessary for kernel-user space structures, since EFI is a C-based ABI. On x86 it doesn't hurt, either, though, so might as well.