linux-kernel - Re: [PATCH v2] crypto: ccp: Abort doing SEV INIT if SNP INIT fails

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Message-ID: <d8275270-cae8-4b35-8088-32da759a5e94@amd.com>
Date: Tue, 18 Mar 2025 15:35:24 -0500
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Tom Lendacky <thomas.lendacky@....com>, seanjc@...gle.com,
 pbonzini@...hat.com, bp@...en8.de, john.allen@....com,
 herbert@...dor.apana.org.au, davem@...emloft.net
Cc: michael.roth@....com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-crypto@...r.kernel.org, linux-coco@...ts.linux.dev
Subject: Re: [PATCH v2] crypto: ccp: Abort doing SEV INIT if SNP INIT fails

Hello Tom,

On 3/18/2025 3:29 PM, Tom Lendacky wrote:
> On 3/18/25 15:07, Ashish Kalra wrote:
>> From: Ashish Kalra <ashish.kalra@....com>
>>
>> If SNP host support (SYSCFG.SNPEn) is set, then the RMP table must
>> be initialized before calling SEV INIT.
>>
>> In other words, if SNP_INIT(_EX) is not issued or fails then
>> SEV INIT will fail if SNP host support (SYSCFG.SNPEn) is enabled.
>>
>> Fixes: 1ca5614b84eed ("crypto: ccp: Add support to initialize the AMD-SP for SEV-SNP")
> 
> Just wondering if this really needs a Fixes: tag. Either way SNP and SEV
> won't be initialized, you're just returning earlier with an error code
> rather than attempting the SEV_INIT(_EX) and getting back a failing
> error code.

Yes, that's true in a way, as continuing with SEV INIT after SNP INIT(_EX) failure
will still cause SEV INIT to fail, we are simply aborting here after 
SNP INIT(_EX) failure, so i will drop the Fixes: tag and post another version.

Thanks,
Ashish

> 
> Thanks,
> Tom
> 
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>>
>> v2:
>> - Fix commit logs.
>> ---
>>  drivers/crypto/ccp/sev-dev.c | 7 ++-----
>>  1 file changed, 2 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index 2e87ca0e292a..a0e3de94704e 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -1112,7 +1112,7 @@ static int __sev_snp_init_locked(int *error)
>>  	if (!sev_version_greater_or_equal(SNP_MIN_API_MAJOR, SNP_MIN_API_MINOR)) {
>>  		dev_dbg(sev->dev, "SEV-SNP support requires firmware version >= %d:%d\n",
>>  			SNP_MIN_API_MAJOR, SNP_MIN_API_MINOR);
>> -		return 0;
>> +		return -EOPNOTSUPP;
>>  	}
>>  
>>  	/* SNP_INIT requires MSR_VM_HSAVE_PA to be cleared on all CPUs. */
>> @@ -1325,12 +1325,9 @@ static int _sev_platform_init_locked(struct sev_platform_init_args *args)
>>  	 */
>>  	rc = __sev_snp_init_locked(&args->error);
>>  	if (rc && rc != -ENODEV) {
>> -		/*
>> -		 * Don't abort the probe if SNP INIT failed,
>> -		 * continue to initialize the legacy SEV firmware.
>> -		 */
>>  		dev_err(sev->dev, "SEV-SNP: failed to INIT rc %d, error %#x\n",
>>  			rc, args->error);
>> +		return rc;
>>  	}
>>  
>>  	/* Defer legacy SEV/SEV-ES support if allowed by caller/module. */