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

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Message-ID: <cd0d79a9-310c-2181-401a-64a67f454c66@amd.com>
Date:   Thu, 4 Aug 2022 08:51:02 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Harald Hoyer <harald@...fian.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     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 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.

Thanks,
Tom

> 
>>
>> [1] 
>> https://lore.kernel.org/lkml/87a0481526e66ddd5f6192cbb43a50708aee2883.1655761627.git.ashish.kalra@amd.com/ 
>>
>>
>> Thanks,
>> Tom
>>
>>>
>>> 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.
>