linux-kernel - Re: [PATCH] crypto: ccp: Load the firmware twice when SEV API version

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Message-ID: <Yu6v+ZFe7zDQjcvZ@kernel.org>
Date:   Sat, 6 Aug 2022 21:16:25 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Harald Hoyer <harald@...fian.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jarkko Sakkinen <jarkko@...fian.com>,
        Brijesh Singh <brijesh.singh@....com>,
        John Allen <john.allen@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        "open list:AMD CRYPTOGRAPHIC COPROCESSOR (CCP) DRIVER - SE..." 
        <linux-crypto@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccp: Load the firmware twice when SEV API
 version < 1.43

On Thu, Aug 04, 2022 at 08:51:02AM -0500, Tom Lendacky wrote:
> On 8/4/22 08:37, Harald Hoyer wrote:
> > Am 04.08.22 um 15:13 schrieb Tom Lendacky:
> > > On 8/3/22 20:02, Jarkko Sakkinen wrote:
> > > > From: Jarkko Sakkinen <jarkko@...fian.com>
> > > > 
> > > > SEV-SNP does not initialize to a legit state, unless the firmware is
> > > > loaded twice, when SEP API version < 1.43, and the firmware is updated
> > > > to a later version. Because of this user space needs to work around
> > > > this with "rmmod && modprobe" combo. Fix this by implementing the
> > > > workaround to the driver.
> > > 
> > > The SNP hypervisor patches are placing a minimum supported version
> > > requirement for the SEV firmware that exceeds the specified version
> > > above [1] (for the reason above, as well as some others), so this patch
> > > is not needed, NAK.
> > 
> > As described in the "Milan Release Notes.txt" of the AMD firmware update
> > package amd_sev_fam19h_model0xh_1.33.03.zip.
> > 
> > "If upgrading to 1.33.01 or later from something older (picking up
> > CSF-1201), it is required that two Download Firmware commands be run to
> > fix the "Committed Version" across the firmware. CSF-1201 fixed a bug
> > where the committed version in the attestation report was incorrect.
> > Performing a single Download Firmware will upgrade the firmware, but
> > performing a second one will correct the committed version. This is a
> > one-time upgrade issue.
> > "
> > 
> > Note that `1.33.01` is not the same version number as "1.51" in [1]. One
> > is the firmware version, the other is the SEV-SNP API version.
> 
> It is the same and are meant to correlate, the 33 is hex => 51.
> 
> > 
> > I am definitely seeing a wrong TCB version, if the firmware is only
> > updated once to `1.33.01` aka "1.51".
> > Reloading the `ccp` module, which triggers another firmware load, cures
> > the problem.
> > 
> > The patch might be wrong, as it might not do the right thing, but the
> > problem and the solution exist.
> > 
> > What is your suggestion then to fix the wrong committed TCB version?
> 
> Hmmm... ok, I see what you're saying. We don't want to have to make everyone
> update their BIOS/firmware to get to a starting level above 1.43 to begin
> with.
> 
> Ok, let me review/comment on the patch.

This was has a bug, and the reference to what Harald denoted
is missing. Hold on for v2. I'll put it out soon.

BR, Jarkko