linux-kernel - Re: [PATCH v2 4/4] virt: Add sev_secret module to expose confidential computing secrets

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Date:   Thu, 7 Oct 2021 17:17:54 +0100
From:   "Dr. David Alan Gilbert" <dgilbert@...hat.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Dov Murik <dovmurik@...ux.ibm.com>, 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>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andrew Scull <ascull@...gle.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
Subject: Re: [PATCH v2 4/4] virt: Add sev_secret module to expose
 confidential computing secrets

* Dave Hansen (dave.hansen@...el.com) wrote:
> On 10/6/21 11:18 PM, Dov Murik wrote:
> > +static int sev_secret_map_area(void)
> > +{
> > +	struct sev_secret *s = sev_secret_get();
> > +	struct linux_efi_coco_secret_area *secret_area;
> > +	u32 secret_area_size;
> > +
> > +	if (efi.coco_secret == EFI_INVALID_TABLE_ADDR) {
> > +		pr_err("Secret area address is not available\n");
> > +		return -EINVAL;
> > +	}
> > +
> > +	secret_area = memremap(efi.coco_secret, sizeof(*secret_area), MEMREMAP_WB);
> > +	if (secret_area == NULL) {
> > +		pr_err("Could not map secret area header\n");
> > +		return -ENOMEM;
> > +	}
> 
> There doesn't seem to be anything truly SEV-specific in here at all.
> Isn't this more accurately called "efi_secret" or something?  What's to
> prevent Intel or an ARM vendor from implementing this?

I don't think anything; although the last discussion I remember on list
with Intel was that Intel preferred some interface with an ioctl to read
the secrets and stuff.  I'm not quite sure if the attestation/secret
delivery order makes sense with TDX, but if it does, then if you could
persuade someone to standardise on this it would be great.

Dave

-- 
Dr. David Alan Gilbert / dgilbert@...hat.com / Manchester, UK