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Date:   Mon, 17 Jan 2022 19:14:34 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Brijesh Singh <brijesh.singh@amd.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
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        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
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        Tobin Feldman-Fitzthum <tobin@ibm.com>,
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Subject: Re: [PATCH v8 30/40] x86/boot: add a pointer to Confidential
 Computing blob in bootparams
Message-ID: <YeWyCtr11rL7dxpT@zn.tnic>
References: <20211210154332.11526-1-brijesh.singh@amd.com>
 <20211210154332.11526-31-brijesh.singh@amd.com>
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In-Reply-To: <20211210154332.11526-31-brijesh.singh@amd.com>
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On Fri, Dec 10, 2021 at 09:43:22AM -0600, Brijesh Singh wrote:
> diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
> index 1ac5acca72ce..bea5cdcdf532 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -188,7 +188,8 @@ struct boot_params {
>  	__u32 ext_ramdisk_image;			/* 0x0c0 */
>  	__u32 ext_ramdisk_size;				/* 0x0c4 */
>  	__u32 ext_cmd_line_ptr;				/* 0x0c8 */
> -	__u8  _pad4[116];				/* 0x0cc */
> +	__u8  _pad4[112];				/* 0x0cc */
> +	__u32 cc_blob_address;				/* 0x13c */
>  	struct edid_info edid_info;			/* 0x140 */
>  	struct efi_info efi_info;			/* 0x1c0 */
>  	__u32 alt_mem_k;				/* 0x1e0 */

Yes, you said that this is a boot/compressed stage -> kernel proper info
pass field but let's document it anyway, please, and say what it is,
just like:

	1E4/004         ALL     scratch                 Scratch field for the kernel setup code

is documented, for example.

And now that I look at it, acpi_rsdp_addr isn't documented either so if
you wanna add it too, while you're at it, that would be nice.

Thx.

-- 
Regards/Gruss,
    Boris.

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