linux-kernel - Re: [PATCH v7 0/5] Allow guest access to EFI confidential computing secret area

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Date:   Tue, 01 Feb 2022 09:24:50 -0500
From:   James Bottomley <jejb@...ux.ibm.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Dov Murik <dovmurik@...ux.ibm.com>
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>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Lenny Szubowicz <lszubowi@...hat.com>,
        Peter Gonda <pgonda@...gle.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, Nayna Jain <nayna@...ux.ibm.com>,
        dougmill@...ux.vnet.ibm.com, gcwilson@...ux.ibm.com,
        gjoyce@....com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        mjg59@...f.ucam.org, mpe@...erman.id.au, dja@...ens.net
Subject: Re: [PATCH v7 0/5] Allow guest access to EFI confidential computing
 secret area

[cc's added]
On Tue, 2022-02-01 at 14:50 +0100, Greg KH wrote:
> On Tue, Feb 01, 2022 at 12:44:08PM +0000, Dov Murik wrote:
[...]
> > # ls -la /sys/kernel/security/coco/efi_secret
> > total 0
> > drwxr-xr-x 2 root root 0 Jun 28 11:55 .
> > drwxr-xr-x 3 root root 0 Jun 28 11:54 ..
> > -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-
> > 06879ce3da0b
> > -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-
> > d3a0b54312c6
> > -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-
> > ff17f78864d2
> 
> Please see my comments on the powerpc version of this type of thing:
> 	
> https://lore.kernel.org/r/20220122005637.28199-1-nayna@linux.ibm.com

If you want a debate, actually cc'ing the people on the other thread
would have been a good start ...

For those added, this patch series is at:

https://lore.kernel.org/all/20220201124413.1093099-1-dovmurik@linux.ibm.com/

> You all need to work together to come up with a unified place for
> this and stop making it platform-specific.

I'm not entirely sure of that.  If you look at the differences between
EFI variables and the COCO proposal: the former has an update API
which, in the case of signed variables, is rather complex and a UC16
content requirement.  The latter is binary data with read only/delete. 
Plus each variable in EFI is described by a GUID, so having a directory
of random guids, some of which behave like COCO secrets and some of
which are EFI variables is going to be incredibly confusing (and also
break all our current listing tools which seems somewhat undesirable).

So we could end up with 

<common path prefix>/efivar
<common path prefix>/coco

To achieve the separation, but I really don't see what this buys us. 
Both filesystems would likely end up with different backends because of
the semantic differences and we can easily start now in different
places (effectively we've already done this for efi variables) and
unify later if that is the chosen direction, so it doesn't look like a
blocker.

> Until then, we can't take this.

I don't believe anyone was asking you to take it.

James