linux-kernel - Re: [PATCH v9 29/43] x86/boot: Add Confidential Computing type to setup

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Date:   Fri, 4 Feb 2022 17:21:51 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     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,
        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>,
        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>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        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 v9 29/43] x86/boot: Add Confidential Computing type to
 setup_data

On Fri, Jan 28, 2022 at 11:17:50AM -0600, 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

So looking at that typedef struct CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION there:

typedef struct {
  UINT32    Header;
  UINT16    Version;
  UINT16    Reserved1;
  UINT64    SecretsPhysicalAddress;
  UINT32    SecretsSize;
  UINT64    CpuidPhysicalAddress;
  UINT32    CpuidLSize;
} CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION;

> + */
> +#define CC_BLOB_SEV_HDR_MAGIC	0x45444d41
> +struct cc_blob_sev_info {
> +	u32 magic;

That's called "Header" there.

> +	u16 version;
> +	u16 reserved;
> +	u64 secrets_phys;
> +	u32 secrets_len;
> +	u32 rsvd1;

You've added that member for padding but the fw blob one doesn't have
it.

But if we get a blob from the firmware and the structure layout differs,
how is this supposed to even work?

> +	u64 cpuid_phys;
> +	u32 cpuid_len;
> +	u32 rsvd2;

That one too.

Or are you going to change the blob layout in ovmf too, to match?

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette