linux-kernel - Re: [PATCH v4 7/7] crypto: ccp: Move SEV/SNP Platform initialization to KVM

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Message-ID: <cc89eda4-d1f8-48e1-9bfd-d550846e2d84@amd.com>
Date: Thu, 20 Feb 2025 14:23:52 -0600
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Tom Lendacky <thomas.lendacky@....com>, seanjc@...gle.com,
 pbonzini@...hat.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 john.allen@....com, herbert@...dor.apana.org.au
Cc: michael.roth@....com, dionnaglaze@...gle.com, nikunj@....com,
 ardb@...nel.org, kevinloughlin@...gle.com, Neeraj.Upadhyay@....com,
 aik@....com, kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-crypto@...r.kernel.org, linux-coco@...ts.linux.dev
Subject: Re: [PATCH v4 7/7] crypto: ccp: Move SEV/SNP Platform initialization
 to KVM

Hello Tom,

On 2/20/2025 2:03 PM, Tom Lendacky wrote:
> On 2/19/25 14:55, Ashish Kalra wrote:
>> From: Ashish Kalra <ashish.kalra@....com>
>>
>> SNP initialization is forced during PSP driver probe purely because SNP
>> can't be initialized if VMs are running.  But the only in-tree user of
>> SEV/SNP functionality is KVM, and KVM depends on PSP driver for the same.
>> Forcing SEV/SNP initialization because a hypervisor could be running
>> legacy non-confidential VMs make no sense.
>>
>> This patch removes SEV/SNP initialization from the PSP driver probe
>> time and moves the requirement to initialize SEV/SNP functionality
>> to KVM if it wants to use SEV/SNP.
>>
>> Suggested-by: Sean Christopherson <seanjc@...gle.com>
>> Reviewed-by: Alexey Kardashevskiy <aik@....com>
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>> ---
>>  drivers/crypto/ccp/sev-dev.c | 25 +------------------------
>>  1 file changed, 1 insertion(+), 24 deletions(-)
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index f0f3e6d29200..99a663dbc2b6 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -1346,18 +1346,13 @@ static int _sev_platform_init_locked(struct sev_platform_init_args *args)
>>  	if (sev->state == SEV_STATE_INIT)
>>  		return 0;
>>  
>> -	/*
>> -	 * Legacy guests cannot be running while SNP_INIT(_EX) is executing,
>> -	 * so perform SEV-SNP initialization at probe time.
>> -	 */
>>  	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);
>> +		dev_err(sev->dev, "SEV-SNP: failed to INIT, continue SEV INIT\n");
> 
> Please don't remove the error information.
> 

The error(s) are already being printed in __sev_snp_init_locked() otherwise the same
error will be printed twice, hence removing it here.

>>  	}
>>  
>>  	/* Defer legacy SEV/SEV-ES support if allowed by caller/module. */
>> @@ -2505,9 +2500,7 @@ EXPORT_SYMBOL_GPL(sev_issue_cmd_external_user);
>>  void sev_pci_init(void)
>>  {
>>  	struct sev_device *sev = psp_master->sev_data;
>> -	struct sev_platform_init_args args = {0};
>>  	u8 api_major, api_minor, build;
>> -	int rc;
>>  
>>  	if (!sev)
>>  		return;
>> @@ -2530,16 +2523,6 @@ void sev_pci_init(void)
>>  			 api_major, api_minor, build,
>>  			 sev->api_major, sev->api_minor, sev->build);
>>  
>> -	/* Initialize the platform */
>> -	args.probe = true;
>> -	rc = sev_platform_init(&args);
>> -	if (rc)
>> -		dev_err(sev->dev, "SEV: failed to INIT error %#x, rc %d\n",
>> -			args.error, rc);
>> -
>> -	dev_info(sev->dev, "SEV%s API:%d.%d build:%d\n", sev->snp_initialized ?
>> -		"-SNP" : "", sev->api_major, sev->api_minor, sev->build);
>> -
>>  	return;
>>  
>>  err:
>> @@ -2550,10 +2533,4 @@ void sev_pci_init(void)
>>  
>>  void sev_pci_exit(void)
>>  {
>> -	struct sev_device *sev = psp_master->sev_data;
>> -
>> -	if (!sev)
>> -		return;
>> -
>> -	sev_firmware_shutdown(sev);
> 
> Should this remain? If there's a bug in KVM that somehow skips the
> shutdown call, then SEV will remain initialized. I think the path is
> safe to call a second time.

Ok.

Thanks,
Ashish