linux-kernel - Re: [PATCH v2 25/25] crypto: ccp: Add the SNP_SET

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Date: Mon, 29 Jan 2024 19:18:54 +0000
From: Liam Merwick <liam.merwick@...cle.com>
To: Michael Roth <michael.roth@....com>, "x86@...nel.org" <x86@...nel.org>
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        Liam Merwick <liam.merwick@...cle.com>
Subject: Re: [PATCH v2 25/25] crypto: ccp: Add the SNP_SET_CONFIG command

On 26/01/2024 04:11, Michael Roth wrote:
> From: Brijesh Singh <brijesh.singh@....com>
> 
> The SEV-SNP firmware provides the SNP_CONFIG command used to set various
> system-wide configuration values for SNP guests, such as the reported
> TCB version used when signing guest attestation reports. Add an
> interface to set this via userspace.
> 
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> Co-developed-by: Alexey Kardashevskiy <aik@....com>
> Signed-off-by: Alexey Kardashevskiy <aik@....com>
> Co-developed-by: Dionna Glaze <dionnaglaze@...gle.com>
> Signed-off-by: Dionna Glaze <dionnaglaze@...gle.com>
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> [mdr: squash in doc patch from Dionna, drop extended request/certificate
>   handling and simplify this to a simple wrapper around SNP_CONFIG fw
>   cmd]
> Signed-off-by: Michael Roth <michael.roth@....com>
> ---
>   Documentation/virt/coco/sev-guest.rst | 13 +++++++++++++
>   drivers/crypto/ccp/sev-dev.c          | 20 ++++++++++++++++++++
>   include/uapi/linux/psp-sev.h          |  1 +
>   3 files changed, 34 insertions(+)
> 
> diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
> index 007ae828aa2a..14c9de997b7d 100644
> --- a/Documentation/virt/coco/sev-guest.rst
> +++ b/Documentation/virt/coco/sev-guest.rst
> @@ -162,6 +162,19 @@ SEV-SNP firmware SNP_COMMIT command. This prevents roll-back to a previously
>   committed firmware version. This will also update the reported TCB to match
>   that of the currently installed firmware.
>   
> +2.6 SNP_SET_CONFIG
> +------------------
> +:Technology: sev-snp
> +:Type: hypervisor ioctl cmd
> +:Parameters (in): struct sev_user_data_snp_config
> +:Returns (out): 0 on success, -negative on error
> +
> +SNP_SET_CONFIG is used to set the system-wide configuration such as
> +reported TCB version in the attestation report. The command is similar
> +to SNP_CONFIG command defined in the SEV-SNP spec. The current values of
> +the firmware parameters affected by this command can be queried via
> +SNP_PLATFORM_STATUS.
> +
>   3. SEV-SNP CPUID Enforcement
>   ============================
>   
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 73ace4064e5a..398ae932aa0b 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -1982,6 +1982,23 @@ static int sev_ioctl_do_snp_commit(struct sev_issue_cmd *argp)
>   	return __sev_do_cmd_locked(SEV_CMD_SNP_COMMIT, &buf, &argp->error);
>   }
>   
> +static int sev_ioctl_do_snp_set_config(struct sev_issue_cmd *argp, bool writable)
> +{
> +	struct sev_device *sev = psp_master->sev_data;

Should this check that psp_master is not NULL? Like the fix for
https://lore.kernel.org/all/20240125231253.3122579-1-kim.phillips@amd.com/

Otherwise,
Reviewed-by: Liam Merwick <liam.merwick@...cle.com>

> +	struct sev_user_data_snp_config config;
> +
> +	if (!sev->snp_initialized || !argp->data)
> +		return -EINVAL;
> +
> +	if (!writable)
> +		return -EPERM;
> +
> +	if (copy_from_user(&config, (void __user *)argp->data, sizeof(config)))
> +		return -EFAULT;
> +
> +	return __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error);
> +}
> +
>   static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
>   {
>   	void __user *argp = (void __user *)arg;
> @@ -2039,6 +2056,9 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
>   	case SNP_COMMIT:
>   		ret = sev_ioctl_do_snp_commit(&input);
>   		break;
> +	case SNP_SET_CONFIG:
> +		ret = sev_ioctl_do_snp_set_config(&input, writable);
> +		break;
>   	default:
>   		ret = -EINVAL;
>   		goto out;
> diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
> index 35c207664e95..b7a2c2ee35b7 100644
> --- a/include/uapi/linux/psp-sev.h
> +++ b/include/uapi/linux/psp-sev.h
> @@ -30,6 +30,7 @@ enum {
>   	SEV_GET_ID2,
>   	SNP_PLATFORM_STATUS,
>   	SNP_COMMIT,
> +	SNP_SET_CONFIG,
>   
>   	SEV_MAX,
>   };