linux-kernel - Re: [PATCH] crypto: ccp - Retry SEV INIT command in case of integrity check failure.

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Date:   Tue, 22 Oct 2019 17:23:46 -0700 (PDT)
From:   David Rientjes <rientjes@...gle.com>
To:     "Singh, Brijesh" <brijesh.singh@....com>
cc:     "Kalra, Ashish" <Ashish.Kalra@....com>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "Hook, Gary" <Gary.Hook@....com>,
        "herbert@...dor.apana.org.au" <herbert@...dor.apana.org.au>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "allison@...utok.net" <allison@...utok.net>,
        "info@...ux.net" <info@...ux.net>,
        "yamada.masahiro@...ionext.com" <yamada.masahiro@...ionext.com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH] crypto: ccp - Retry SEV INIT command in case of integrity
 check failure.

On Tue, 22 Oct 2019, Singh, Brijesh wrote:

> >>>> From: Ashish Kalra <ashish.kalra@....com>
> >>>>
> >>>> SEV INIT command loads the SEV related persistent data from NVS
> >>>> and initializes the platform context. The firmware validates the
> >>>> persistent state. If validation fails, the firmware will reset
> >>>> the persisent state and return an integrity check failure status.
> >>>>
> >>>> At this point, a subsequent INIT command should succeed, so retry
> >>>> the command. The INIT command retry is only done during driver
> >>>> initialization.
> >>>>
> >>>> Additional enums along with SEV_RET_SECURE_DATA_INVALID are added
> >>>> to sev_ret_code to maintain continuity and relevance of enum values.
> >>>>
> >>>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> >>>> ---
> >>>>    drivers/crypto/ccp/psp-dev.c | 12 ++++++++++++
> >>>>    include/uapi/linux/psp-sev.h |  3 +++
> >>>>    2 files changed, 15 insertions(+)
> >>>>
> >>>> diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
> >>>> index 6b17d179ef8a..f9318d4482f2 100644
> >>>> --- a/drivers/crypto/ccp/psp-dev.c
> >>>> +++ b/drivers/crypto/ccp/psp-dev.c
> >>>> @@ -1064,6 +1064,18 @@ void psp_pci_init(void)
> >>>>    
> >>>>    	/* Initialize the platform */
> >>>>    	rc = sev_platform_init(&error);
> >>>> +	if (rc && (error == SEV_RET_SECURE_DATA_INVALID)) {
> >>>> +		/*
> >>>> +		 * INIT command returned an integrity check failure
> >>>> +		 * status code, meaning that firmware load and
> >>>> +		 * validation of SEV related persistent data has
> >>>> +		 * failed and persistent state has been erased.
> >>>> +		 * Retrying INIT command here should succeed.
> >>>> +		 */
> >>>> +		dev_dbg(sp->dev, "SEV: retrying INIT command");
> >>>> +		rc = sev_platform_init(&error);
> >>>> +	}
> >>>> +
> >>>>    	if (rc) {
> >>>>    		dev_err(sp->dev, "SEV: failed to INIT error %#x\n", error);
> >>>>    		return;
> >>>
> >>> Curious why this isn't done in __sev_platform_init_locked() since
> >>> sev_platform_init() can be called when loading the kvm module and the same
> >>> init failure can happen that way.
> >>>
> >>
> >> The FW initialization (aka PLATFORM_INIT) is called in the following
> >> code paths:
> >>
> >> 1. During system boot up
> >>
> >> and
> >>
> >> 2. After the platform reset command is issued
> >>
> >> The patch takes care of #1. Based on the spec, platform reset command
> >> should erase the persistent data and the PLATFORM_INIT should *not* fail
> >> with SEV_RET_SECURE_DATA_INVALID error code. So, I am not able to see
> >> any  strong reason to move the retry code in
> >> __sev_platform_init_locked().
> >>
> > 
> > Hmm, is the sev_platform_init() call in sev_guest_init() intended to do
> > SEV_CMD_INIT only after platform reset?  I was under the impression it was
> > done in case any previous init failed.
> > 
> 
> 
> The PLATFORM_INIT command is allowed only when FW is in UINIT state. On
> boot, the FW will be in UNINIT state and similarly after the platform 
> reset command the FW goes back to UNINIT state.
> 
> The __sev_platform_init_locked() checks the FW state before issuing the
> command, if FW is already in INIT state then it returns immediately.
> 

Ah, got it, thanks.

Acked-by: David Rientjes <rientjes@...gle.com>