linux-kernel - Re: [Part2 PATCH v5.1 12.6/31] crypto: ccp: Implement SEV_PDH

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Message-ID: <d4be8769-405e-d607-7bd9-ecfe3a48f646@amd.com>
Date:   Thu, 12 Oct 2017 15:21:04 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...e.de>
Cc:     brijesh.singh@....com, Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Gary Hook <gary.hook@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-crypto@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [Part2 PATCH v5.1 12.6/31] crypto: ccp: Implement SEV_PDH_GEN
 ioctl command



On 10/12/17 1:48 PM, Borislav Petkov wrote:
...
> On Fri, Oct 06, 2017 at 08:06:04PM -0500, Brijesh Singh wrote:
>> The SEV_PDH_GEN command is used to re-generate the Platform
>> Diffie-Hellman (PDH) key. The command is defined in SEV spec section
>> 5.9.
>>
>> Cc: Paolo Bonzini <pbonzini@...hat.com>
>> Cc: "Radim Krčmář" <rkrcmar@...hat.com>
>> Cc: Borislav Petkov <bp@...e.de>
>> Cc: Herbert Xu <herbert@...dor.apana.org.au>
>> Cc: Gary Hook <gary.hook@....com>
>> Cc: Tom Lendacky <thomas.lendacky@....com>
>> Cc: linux-crypto@...r.kernel.org
>> Cc: kvm@...r.kernel.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> ---
>>  drivers/crypto/ccp/psp-dev.c | 32 ++++++++++++++++++++++++++++++++
>>  1 file changed, 32 insertions(+)
>>
>> diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
>> index 03d7bd03ad58..28efb7a9245a 100644
>> --- a/drivers/crypto/ccp/psp-dev.c
>> +++ b/drivers/crypto/ccp/psp-dev.c
>> @@ -271,6 +271,34 @@ static int sev_ioctl_pek_gen(struct sev_issue_cmd *argp)
>>  	return ret;
>>  }
>>  
>> +static int sev_ioctl_pdh_gen(struct sev_issue_cmd *argp)
>> +{
>> +	int ret, state, do_shutdown = 0;
>> +
>> +	/*
>> +	 * PDH_GEN command can be issued when platform is in INIT or WORKING
>> +	 * state. If we are in UNINIT state then transition in INIT state
>> +	 * before issuing the command.
>> +	 */
>> +	ret = sev_platform_get_state(&state, &argp->error);
>> +	if (ret)
>> +		return ret;
>> +
> Why isn't this function doing:
>
>         if (state == SEV_STATE_WORKING) {
>                 return -EBUSY;
>
> like the PEK_GEN one?

We need to follow the platform state machine logic defined in SEV spec
section 5.1.2. The PEK_GEN can not be issued when platform is in WORKING
state because the command actually re-generate the identity of the
platform itself (in other words re-generate the Platform Endorsement
Key). Whereas, the PDH_GEN command is used for re-generating Platform
Diffie-Hellman Key which can be changed while the guest is running.

> Because if so, you can convert it and the PEK_GEN one into a single
> function doing the work and wrappers handing in the command to avoid the
> code duplication.
>
>> +	if (state == SEV_STATE_UNINIT) {
>> +		ret = sev_firmware_init(&argp->error);
>> +		if (ret)
>> +			return ret;
>> +		do_shutdown = 1;
>> +	}
>> +
>> +	ret = sev_handle_cmd(SEV_CMD_PDH_GEN, 0, &argp->error);
>> +
>> +	if (do_shutdown)
>> +		sev_handle_cmd(SEV_CMD_SHUTDOWN, 0, NULL);
>> +
>> +	return ret;
>> +}
>> +
>>  static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
>>  {
>>  	void __user *argp = (void __user *)arg;
>> @@ -300,6 +328,10 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
>>  		ret = sev_ioctl_pek_gen(&input);
>>  		break;
>>  	}
>> +	case SEV_PDH_GEN: {
>> +		ret = sev_ioctl_pdh_gen(&input);
>> +		break;
>> +	}
> And those curly braces can go, as before.
>