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

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Message-ID: <YuvMEm4PwTtSL8Ig@jpiotrowski-Surface-Book-3>
Date:   Thu, 4 Aug 2022 15:39:30 +0200
From:   Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     Jarkko Sakkinen <jarkko@...nel.org>,
        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 08:13:35AM -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.
> 
> 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.
> 
> [1] https://lore.kernel.org/lkml/87a0481526e66ddd5f6192cbb43a50708aee2883.1655761627.git.ashish.kalra@amd.com/
> 
> Thanks,
> Tom

Hi Tom,

Is there any particular reason for this restriction? Does SNP not work with API
version <v1.51? Do you have a link to a changelog that describes the changes
between different firmware versions?

Thanks,
Jeremi

> 
> > 
> > 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
> > @@ -76,6 +76,9 @@ static void *sev_es_tmr;
> >   #define NV_LENGTH (32 * 1024)
> >   static void *sev_init_ex_buffer;
> > +/*
> > + * SEV API version >= maj.min?
> > + */
> >   static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
> >   {
> >   	struct sev_device *sev = psp_master->sev_data;
> > @@ -89,6 +92,14 @@ static inline bool sev_version_greater_or_equal(u8 maj, u8 min)
> >   	return false;
> >   }
> > +/*
> > + * SEV API version < maj.min?
> > + */
> > +static inline bool sev_version_less(u8 maj, u8 min)
> > +{
> > +	return !sev_version_greater_or_equal(maj, min);
> > +}
> > +
> >   static void sev_irq_handler(int irq, void *data, unsigned int status)
> >   {
> >   	struct sev_device *sev = data;
> > @@ -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();
> >   	/* If an init_ex_path is provided rely on INIT_EX for PSP initialization
> >   	 * instead of INIT.