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

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Message-ID: <Yu6wJKS39HyuD4XN@kernel.org>
Date:   Sat, 6 Aug 2022 21:17:08 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Jarkko Sakkinen <jarkko@...fian.com>,
        Harald Hoyer <harald@...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 09:59:44AM -0500, Tom Lendacky wrote:
> 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.
> > 
> > Reported-by: Harald Hoyer <harald@...fian.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@...fian.com>
> > ---
> >   drivers/crypto/ccp/sev-dev.c | 22 +++++++++++++++++++---
> >   1 file changed, 19 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> > index 799b476fc3e8..f2abb7439dde 100644
> > --- a/drivers/crypto/ccp/sev-dev.c
> > +++ b/drivers/crypto/ccp/sev-dev.c
> 
> > @@ -1274,6 +1285,7 @@ void sev_pci_init(void)
> >   {
> >   	struct sev_device *sev = psp_master->sev_data;
> >   	int error, rc;
> > +	int i;
> >   	if (!sev)
> >   		return;
> > @@ -1283,9 +1295,13 @@ void sev_pci_init(void)
> >   	if (sev_get_api_version())
> >   		goto err;
> > -	if (sev_version_greater_or_equal(0, 15) &&
> > -	    sev_update_firmware(sev->dev) == 0)
> > -		sev_get_api_version();
> > +	/*
> > +	 * SEV-SNP does not work properly before loading the FW twice in the API
> > +	 * versions older than SEV 1.43.
> > +	 */
> > +	for (i = 0; i < sev_version_greater_or_equal(0, 15) + sev_version_less(1, 43); i++)
> > +		if (sev_update_firmware(sev->dev) == 0)
> > +			sev_get_api_version();
> 
> I prefer to have this logic in the sev_update_firmware() function.
> 
> And while the loop is correct, it isn't obvious. Something in
> sev_update_firmware() that just does:
> 
> 	ret = sev_do_cmd(SEV_CMD_DOWNLOAD_FIRMWARE, data, &error);
> 
> 	if (!ret && sev_version_greater_or_equal(0, 15) && sev_version_less(1, 43))
> 		ret = sev_do_cmd(SEV_CMD_DOWNLOAD_FIRMWARE, data, &error);
> 
> And place a comment before the second command that references the reason
> for the second download.
 
OK, I'll do that. Thank you.

BR, Jarkko