linux-kernel - Re: [PATCH v3 2/3] efi: Reserve confidential computing secret area

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Message-ID: <6396fec0-7a43-1cc7-44bb-064ab80d2139@linux.ibm.com>
Date:   Wed, 20 Oct 2021 09:51:31 +0300
From:   Dov Murik <dovmurik@...ux.ibm.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     linux-efi@...r.kernel.org, Borislav Petkov <bp@...e.de>,
        Ashish Kalra <ashish.kalra@....com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Ard Biesheuvel <ardb@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Andrew Scull <ascull@...gle.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@...ux.ibm.com>,
        Jim Cadden <jcadden@....com>,
        Daniele Buono <dbuono@...ux.vnet.ibm.com>,
        linux-coco@...ts.linux.dev, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Dov Murik <dovmurik@...ux.ibm.com>
Subject: Re: [PATCH v3 2/3] efi: Reserve confidential computing secret area



On 14/10/2021 16:36, Greg KH wrote:
> On Thu, Oct 14, 2021 at 01:08:47PM +0000, Dov Murik wrote:
>> When efi-stub copies an EFI-provided confidential computing (coco)
>> secret area, reserve that memory block for future use within the kernel.
>>
>> Signed-off-by: Dov Murik <dovmurik@...ux.ibm.com>
>> ---
>>  arch/x86/platform/efi/efi.c   |  1 +
>>  drivers/firmware/efi/Makefile |  2 +-
>>  drivers/firmware/efi/coco.c   | 41 +++++++++++++++++++++++++++++++++++
>>  drivers/firmware/efi/efi.c    |  4 ++++
>>  include/linux/efi.h           |  3 +++
>>  5 files changed, 50 insertions(+), 1 deletion(-)
>>  create mode 100644 drivers/firmware/efi/coco.c
>>
>> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
>> index 147c30a81f15..35e082e5f603 100644
>> --- a/arch/x86/platform/efi/efi.c
>> +++ b/arch/x86/platform/efi/efi.c
>> @@ -93,6 +93,7 @@ static const unsigned long * const efi_tables[] = {
>>  #ifdef CONFIG_LOAD_UEFI_KEYS
>>  	&efi.mokvar_table,
>>  #endif
>> +	&efi.coco_secret,
> 
> Shouldn't this depend on CONFIG_EFI_SECRET?
> 
> Why build all of this code if that option is not enabled?
> 

Thanks Greg for noticing this.  Fixed in v4 [1] where the code
is guarded with #ifdefs (so it's not built by default).

[1] https://lore.kernel.org/linux-coco/20211020061408.3447533-1-dovmurik@linux.ibm.com/

-Dov