[v2] Add SEV-SNP CipherTextHiding feature support

[PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command

Posted by Ashish Kalra 1 year, 4 months ago

From: Ashish Kalra <ashish.kalra@amd.com>

The FEATURE_INFO command provides host and guests a programmatic means
to learn about the supported features of the currently loaded firmware.
FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
Instead of using the CPUID instruction to retrieve Fn8000_0024,
software can use FEATURE_INFO.

Host/Hypervisor would use the FEATURE_INFO command, while guests would
actually issue the CPUID instruction.

The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
the hypervisor can filter Fn8000_0024. The firmware will examine
Fn8000_0024 and apply its CPUID policy.

During CCP module initialization, after firmware update, the SNP
platform status and feature information from CPUID 0x8000_0024,
sub-function 0, are cached in the sev_device structure.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
 drivers/crypto/ccp/sev-dev.h |  3 +++
 include/linux/psp-sev.h      | 29 ++++++++++++++++++++++
 3 files changed, 79 insertions(+)

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index af018afd9cd7..564daf748293 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
 	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
 	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
 	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
+	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct snp_feature_info);
 	default:				return 0;
 	}
 
@@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
 	wrmsrl(MSR_VM_HSAVE_PA, 0);
 }
 
+static void snp_get_platform_data(void)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_data_snp_feature_info snp_feat_info;
+	struct snp_feature_info *feat_info;
+	struct sev_data_snp_addr buf;
+	int error = 0, rc;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return;
+
+	/*
+	 * The output buffer must be firmware page if SEV-SNP is
+	 * initialized.
+	 */
+	if (sev->snp_initialized)
+		return;
+
+	buf.address = __psp_pa(&sev->snp_plat_status);
+	rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
+
+	/*
+	 * Do feature discovery of the currently loaded firmware,
+	 * and cache feature information from CPUID 0x8000_0024,
+	 * sub-function 0.
+	 */
+	if (!rc && sev->snp_plat_status.feature_info) {
+		/*
+		 * Use dynamically allocated structure for the SNP_FEATURE_INFO
+		 * command to handle any alignment and page boundary check
+		 * requirements.
+		 */
+		feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
+		snp_feat_info.length = sizeof(snp_feat_info);
+		snp_feat_info.ecx_in = 0;
+		snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
+
+		rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
+		if (!rc)
+			sev->feat_info = *feat_info;
+		kfree(feat_info);
+	}
+}
+
 static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
 {
 	struct sev_data_range_list *range_list = arg;
@@ -2415,6 +2460,8 @@ void sev_pci_init(void)
 			 api_major, api_minor, build,
 			 sev->api_major, sev->api_minor, sev->build);
 
+	snp_get_platform_data();
+
 	/* Initialize the platform */
 	args.probe = true;
 	rc = sev_platform_init(&args);
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 3e4e5574e88a..1c1a51e52d2b 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -57,6 +57,9 @@ struct sev_device {
 	bool cmd_buf_backup_active;
 
 	bool snp_initialized;
+
+	struct sev_user_data_snp_status snp_plat_status;
+	struct snp_feature_info feat_info;
 };
 
 int sev_dev_init(struct psp_device *psp);
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 903ddfea8585..6068a89839e1 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -107,6 +107,7 @@ enum sev_cmd {
 	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
 	SEV_CMD_SNP_COMMIT		= 0x0CB,
 	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
+	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
 
 	SEV_CMD_MAX,
 };
@@ -812,6 +813,34 @@ struct sev_data_snp_commit {
 	u32 len;
 } __packed;
 
+/**
+ * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
+ *
+ * @length: len of the command buffer read by the PSP
+ * @ecx_in: subfunction index
+ * @feature_info_paddr : SPA of the FEATURE_INFO structure
+ */
+struct sev_data_snp_feature_info {
+	u32 length;
+	u32 ecx_in;
+	u64 feature_info_paddr;
+} __packed;
+
+/**
+ * struct feature_info - FEATURE_INFO structure
+ *
+ * @eax: output of SNP_FEATURE_INFO command
+ * @ebx: output of SNP_FEATURE_INFO command
+ * @ecx: output of SNP_FEATURE_INFO command
+ * #edx: output of SNP_FEATURE_INFO command
+ */
+struct snp_feature_info {
+	u32 eax;
+	u32 ebx;
+	u32 ecx;
+	u32 edx;
+} __packed;
+
 #ifdef CONFIG_CRYPTO_DEV_SP_PSP
 
 /**
-- 
2.34.1

Re: [PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command

Posted by Tom Lendacky 1 year, 4 months ago

On 9/17/24 15:16, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
> 
> The FEATURE_INFO command provides host and guests a programmatic means
> to learn about the supported features of the currently loaded firmware.
> FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
> Instead of using the CPUID instruction to retrieve Fn8000_0024,
> software can use FEATURE_INFO.
> 
> Host/Hypervisor would use the FEATURE_INFO command, while guests would
> actually issue the CPUID instruction.
> 
> The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
> page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
> the hypervisor can filter Fn8000_0024. The firmware will examine
> Fn8000_0024 and apply its CPUID policy.
> 
> During CCP module initialization, after firmware update, the SNP
> platform status and feature information from CPUID 0x8000_0024,
> sub-function 0, are cached in the sev_device structure.
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> ---
>  drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
>  drivers/crypto/ccp/sev-dev.h |  3 +++
>  include/linux/psp-sev.h      | 29 ++++++++++++++++++++++
>  3 files changed, 79 insertions(+)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index af018afd9cd7..564daf748293 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
>  	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
>  	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
>  	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
> +	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct snp_feature_info);
>  	default:				return 0;
>  	}
>  
> @@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
>  	wrmsrl(MSR_VM_HSAVE_PA, 0);
>  }
>  
> +static void snp_get_platform_data(void)
> +{
> +	struct sev_device *sev = psp_master->sev_data;
> +	struct sev_data_snp_feature_info snp_feat_info;
> +	struct snp_feature_info *feat_info;
> +	struct sev_data_snp_addr buf;
> +	int error = 0, rc;
> +
> +	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
> +		return;
> +
> +	/*
> +	 * The output buffer must be firmware page if SEV-SNP is
> +	 * initialized.

This comment is a little confusing relative to the "if" check that is
performed. Add some more detail about what this check is for.

But... would this ever need to be called after SNP_INIT? Would we want
to call this again after, say, a DOWNLOAD_FIRMWARE command?

Thanks,
Tom

> +	 */
> +	if (sev->snp_initialized)
> +		return;
> +
> +	buf.address = __psp_pa(&sev->snp_plat_status);
> +	rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
> +
> +	/*
> +	 * Do feature discovery of the currently loaded firmware,
> +	 * and cache feature information from CPUID 0x8000_0024,
> +	 * sub-function 0.
> +	 */
> +	if (!rc && sev->snp_plat_status.feature_info) {
> +		/*
> +		 * Use dynamically allocated structure for the SNP_FEATURE_INFO
> +		 * command to handle any alignment and page boundary check
> +		 * requirements.
> +		 */
> +		feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
> +		snp_feat_info.length = sizeof(snp_feat_info);
> +		snp_feat_info.ecx_in = 0;
> +		snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
> +
> +		rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
> +		if (!rc)
> +			sev->feat_info = *feat_info;
> +		kfree(feat_info);
> +	}
> +}
> +
>  static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>  {
>  	struct sev_data_range_list *range_list = arg;
> @@ -2415,6 +2460,8 @@ void sev_pci_init(void)
>  			 api_major, api_minor, build,
>  			 sev->api_major, sev->api_minor, sev->build);
>  
> +	snp_get_platform_data();
> +
>  	/* Initialize the platform */
>  	args.probe = true;
>  	rc = sev_platform_init(&args);
> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
> index 3e4e5574e88a..1c1a51e52d2b 100644
> --- a/drivers/crypto/ccp/sev-dev.h
> +++ b/drivers/crypto/ccp/sev-dev.h
> @@ -57,6 +57,9 @@ struct sev_device {
>  	bool cmd_buf_backup_active;
>  
>  	bool snp_initialized;
> +
> +	struct sev_user_data_snp_status snp_plat_status;
> +	struct snp_feature_info feat_info;
>  };
>  
>  int sev_dev_init(struct psp_device *psp);
> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
> index 903ddfea8585..6068a89839e1 100644
> --- a/include/linux/psp-sev.h
> +++ b/include/linux/psp-sev.h
> @@ -107,6 +107,7 @@ enum sev_cmd {
>  	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
>  	SEV_CMD_SNP_COMMIT		= 0x0CB,
>  	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
> +	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
>  
>  	SEV_CMD_MAX,
>  };
> @@ -812,6 +813,34 @@ struct sev_data_snp_commit {
>  	u32 len;
>  } __packed;
>  
> +/**
> + * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
> + *
> + * @length: len of the command buffer read by the PSP
> + * @ecx_in: subfunction index
> + * @feature_info_paddr : SPA of the FEATURE_INFO structure
> + */
> +struct sev_data_snp_feature_info {
> +	u32 length;
> +	u32 ecx_in;
> +	u64 feature_info_paddr;
> +} __packed;
> +
> +/**
> + * struct feature_info - FEATURE_INFO structure
> + *
> + * @eax: output of SNP_FEATURE_INFO command
> + * @ebx: output of SNP_FEATURE_INFO command
> + * @ecx: output of SNP_FEATURE_INFO command
> + * #edx: output of SNP_FEATURE_INFO command
> + */
> +struct snp_feature_info {
> +	u32 eax;
> +	u32 ebx;
> +	u32 ecx;
> +	u32 edx;
> +} __packed;
> +
>  #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>  
>  /**

Re: [PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command

Posted by Tom Lendacky 1 year, 4 months ago

On 10/2/24 16:18, Tom Lendacky wrote:
> On 9/17/24 15:16, Ashish Kalra wrote:
>> From: Ashish Kalra <ashish.kalra@amd.com>
>>
>> The FEATURE_INFO command provides host and guests a programmatic means
>> to learn about the supported features of the currently loaded firmware.
>> FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
>> Instead of using the CPUID instruction to retrieve Fn8000_0024,
>> software can use FEATURE_INFO.
>>
>> Host/Hypervisor would use the FEATURE_INFO command, while guests would
>> actually issue the CPUID instruction.
>>
>> The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
>> page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
>> the hypervisor can filter Fn8000_0024. The firmware will examine
>> Fn8000_0024 and apply its CPUID policy.
>>
>> During CCP module initialization, after firmware update, the SNP
>> platform status and feature information from CPUID 0x8000_0024,
>> sub-function 0, are cached in the sev_device structure.
>>
>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>> ---
>>  drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
>>  drivers/crypto/ccp/sev-dev.h |  3 +++
>>  include/linux/psp-sev.h      | 29 ++++++++++++++++++++++
>>  3 files changed, 79 insertions(+)
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index af018afd9cd7..564daf748293 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
>>  	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
>>  	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
>>  	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
>> +	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct snp_feature_info);
>>  	default:				return 0;
>>  	}
>>  
>> @@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
>>  	wrmsrl(MSR_VM_HSAVE_PA, 0);
>>  }
>>  
>> +static void snp_get_platform_data(void)
>> +{
>> +	struct sev_device *sev = psp_master->sev_data;
>> +	struct sev_data_snp_feature_info snp_feat_info;
>> +	struct snp_feature_info *feat_info;
>> +	struct sev_data_snp_addr buf;
>> +	int error = 0, rc;
>> +
>> +	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>> +		return;
>> +
>> +	/*
>> +	 * The output buffer must be firmware page if SEV-SNP is
>> +	 * initialized.
> 
> This comment is a little confusing relative to the "if" check that is
> performed. Add some more detail about what this check is for.
> 
> But... would this ever need to be called after SNP_INIT? Would we want
> to call this again after, say, a DOWNLOAD_FIRMWARE command?

Although, as I hit send I realized that we only do DOWNLOAD_FIRMWARE
before SNP is initialized (currently).

Thanks,
Tom

> 
> Thanks,
> Tom
> 
>> +	 */
>> +	if (sev->snp_initialized)
>> +		return;
>> +
>> +	buf.address = __psp_pa(&sev->snp_plat_status);
>> +	rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
>> +
>> +	/*
>> +	 * Do feature discovery of the currently loaded firmware,
>> +	 * and cache feature information from CPUID 0x8000_0024,
>> +	 * sub-function 0.
>> +	 */
>> +	if (!rc && sev->snp_plat_status.feature_info) {
>> +		/*
>> +		 * Use dynamically allocated structure for the SNP_FEATURE_INFO
>> +		 * command to handle any alignment and page boundary check
>> +		 * requirements.
>> +		 */
>> +		feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
>> +		snp_feat_info.length = sizeof(snp_feat_info);
>> +		snp_feat_info.ecx_in = 0;
>> +		snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
>> +
>> +		rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
>> +		if (!rc)
>> +			sev->feat_info = *feat_info;
>> +		kfree(feat_info);
>> +	}
>> +}
>> +
>>  static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>>  {
>>  	struct sev_data_range_list *range_list = arg;
>> @@ -2415,6 +2460,8 @@ void sev_pci_init(void)
>>  			 api_major, api_minor, build,
>>  			 sev->api_major, sev->api_minor, sev->build);
>>  
>> +	snp_get_platform_data();
>> +
>>  	/* Initialize the platform */
>>  	args.probe = true;
>>  	rc = sev_platform_init(&args);
>> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
>> index 3e4e5574e88a..1c1a51e52d2b 100644
>> --- a/drivers/crypto/ccp/sev-dev.h
>> +++ b/drivers/crypto/ccp/sev-dev.h
>> @@ -57,6 +57,9 @@ struct sev_device {
>>  	bool cmd_buf_backup_active;
>>  
>>  	bool snp_initialized;
>> +
>> +	struct sev_user_data_snp_status snp_plat_status;
>> +	struct snp_feature_info feat_info;
>>  };
>>  
>>  int sev_dev_init(struct psp_device *psp);
>> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
>> index 903ddfea8585..6068a89839e1 100644
>> --- a/include/linux/psp-sev.h
>> +++ b/include/linux/psp-sev.h
>> @@ -107,6 +107,7 @@ enum sev_cmd {
>>  	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
>>  	SEV_CMD_SNP_COMMIT		= 0x0CB,
>>  	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
>> +	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
>>  
>>  	SEV_CMD_MAX,
>>  };
>> @@ -812,6 +813,34 @@ struct sev_data_snp_commit {
>>  	u32 len;
>>  } __packed;
>>  
>> +/**
>> + * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
>> + *
>> + * @length: len of the command buffer read by the PSP
>> + * @ecx_in: subfunction index
>> + * @feature_info_paddr : SPA of the FEATURE_INFO structure
>> + */
>> +struct sev_data_snp_feature_info {
>> +	u32 length;
>> +	u32 ecx_in;
>> +	u64 feature_info_paddr;
>> +} __packed;
>> +
>> +/**
>> + * struct feature_info - FEATURE_INFO structure
>> + *
>> + * @eax: output of SNP_FEATURE_INFO command
>> + * @ebx: output of SNP_FEATURE_INFO command
>> + * @ecx: output of SNP_FEATURE_INFO command
>> + * #edx: output of SNP_FEATURE_INFO command
>> + */
>> +struct snp_feature_info {
>> +	u32 eax;
>> +	u32 ebx;
>> +	u32 ecx;
>> +	u32 edx;
>> +} __packed;
>> +
>>  #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>>  
>>  /**

Re: [PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command

Posted by Kalra, Ashish 1 year, 4 months ago

Hello Tom,

On 10/2/2024 4:19 PM, Tom Lendacky wrote:
> On 10/2/24 16:18, Tom Lendacky wrote:
>> On 9/17/24 15:16, Ashish Kalra wrote:
>>> From: Ashish Kalra <ashish.kalra@amd.com>
>>>
>>> The FEATURE_INFO command provides host and guests a programmatic means
>>> to learn about the supported features of the currently loaded firmware.
>>> FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
>>> Instead of using the CPUID instruction to retrieve Fn8000_0024,
>>> software can use FEATURE_INFO.
>>>
>>> Host/Hypervisor would use the FEATURE_INFO command, while guests would
>>> actually issue the CPUID instruction.
>>>
>>> The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
>>> page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
>>> the hypervisor can filter Fn8000_0024. The firmware will examine
>>> Fn8000_0024 and apply its CPUID policy.
>>>
>>> During CCP module initialization, after firmware update, the SNP
>>> platform status and feature information from CPUID 0x8000_0024,
>>> sub-function 0, are cached in the sev_device structure.
>>>
>>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>>> ---
>>>  drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
>>>  drivers/crypto/ccp/sev-dev.h |  3 +++
>>>  include/linux/psp-sev.h      | 29 ++++++++++++++++++++++
>>>  3 files changed, 79 insertions(+)
>>>
>>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>>> index af018afd9cd7..564daf748293 100644
>>> --- a/drivers/crypto/ccp/sev-dev.c
>>> +++ b/drivers/crypto/ccp/sev-dev.c
>>> @@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
>>>  	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
>>>  	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
>>>  	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
>>> +	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct snp_feature_info);
>>>  	default:				return 0;
>>>  	}
>>>  
>>> @@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
>>>  	wrmsrl(MSR_VM_HSAVE_PA, 0);
>>>  }
>>>  
>>> +static void snp_get_platform_data(void)
>>> +{
>>> +	struct sev_device *sev = psp_master->sev_data;
>>> +	struct sev_data_snp_feature_info snp_feat_info;
>>> +	struct snp_feature_info *feat_info;
>>> +	struct sev_data_snp_addr buf;
>>> +	int error = 0, rc;
>>> +
>>> +	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>>> +		return;
>>> +
>>> +	/*
>>> +	 * The output buffer must be firmware page if SEV-SNP is
>>> +	 * initialized.
>> This comment is a little confusing relative to the "if" check that is
>> performed. Add some more detail about what this check is for.
>>
>> But... would this ever need to be called after SNP_INIT? Would we want
>> to call this again after, say, a DOWNLOAD_FIRMWARE command?
> Although, as I hit send I realized that we only do DOWNLOAD_FIRMWARE
> before SNP is initialized (currently).

We do have DOWNLOAD_FIRMWARE_EX support coming up which can/will happen after SNP_INIT, but there we can still use SEV's PLATFORM_DATA command to get (updated) SEV/SNP firmware version.

Thanks, Ashish

>
> Thanks,
> Tom
>
>> Thanks,
>> Tom
>>
>>> +	 */
>>> +	if (sev->snp_initialized)
>>> +		return;
>>> +
>>> +	buf.address = __psp_pa(&sev->snp_plat_status);
>>> +	rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
>>> +
>>> +	/*
>>> +	 * Do feature discovery of the currently loaded firmware,
>>> +	 * and cache feature information from CPUID 0x8000_0024,
>>> +	 * sub-function 0.
>>> +	 */
>>> +	if (!rc && sev->snp_plat_status.feature_info) {
>>> +		/*
>>> +		 * Use dynamically allocated structure for the SNP_FEATURE_INFO
>>> +		 * command to handle any alignment and page boundary check
>>> +		 * requirements.
>>> +		 */
>>> +		feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
>>> +		snp_feat_info.length = sizeof(snp_feat_info);
>>> +		snp_feat_info.ecx_in = 0;
>>> +		snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
>>> +
>>> +		rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
>>> +		if (!rc)
>>> +			sev->feat_info = *feat_info;
>>> +		kfree(feat_info);
>>> +	}
>>> +}
>>> +
>>>  static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>>>  {
>>>  	struct sev_data_range_list *range_list = arg;
>>> @@ -2415,6 +2460,8 @@ void sev_pci_init(void)
>>>  			 api_major, api_minor, build,
>>>  			 sev->api_major, sev->api_minor, sev->build);
>>>  
>>> +	snp_get_platform_data();
>>> +
>>>  	/* Initialize the platform */
>>>  	args.probe = true;
>>>  	rc = sev_platform_init(&args);
>>> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
>>> index 3e4e5574e88a..1c1a51e52d2b 100644
>>> --- a/drivers/crypto/ccp/sev-dev.h
>>> +++ b/drivers/crypto/ccp/sev-dev.h
>>> @@ -57,6 +57,9 @@ struct sev_device {
>>>  	bool cmd_buf_backup_active;
>>>  
>>>  	bool snp_initialized;
>>> +
>>> +	struct sev_user_data_snp_status snp_plat_status;
>>> +	struct snp_feature_info feat_info;
>>>  };
>>>  
>>>  int sev_dev_init(struct psp_device *psp);
>>> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
>>> index 903ddfea8585..6068a89839e1 100644
>>> --- a/include/linux/psp-sev.h
>>> +++ b/include/linux/psp-sev.h
>>> @@ -107,6 +107,7 @@ enum sev_cmd {
>>>  	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
>>>  	SEV_CMD_SNP_COMMIT		= 0x0CB,
>>>  	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
>>> +	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
>>>  
>>>  	SEV_CMD_MAX,
>>>  };
>>> @@ -812,6 +813,34 @@ struct sev_data_snp_commit {
>>>  	u32 len;
>>>  } __packed;
>>>  
>>> +/**
>>> + * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
>>> + *
>>> + * @length: len of the command buffer read by the PSP
>>> + * @ecx_in: subfunction index
>>> + * @feature_info_paddr : SPA of the FEATURE_INFO structure
>>> + */
>>> +struct sev_data_snp_feature_info {
>>> +	u32 length;
>>> +	u32 ecx_in;
>>> +	u64 feature_info_paddr;
>>> +} __packed;
>>> +
>>> +/**
>>> + * struct feature_info - FEATURE_INFO structure
>>> + *
>>> + * @eax: output of SNP_FEATURE_INFO command
>>> + * @ebx: output of SNP_FEATURE_INFO command
>>> + * @ecx: output of SNP_FEATURE_INFO command
>>> + * #edx: output of SNP_FEATURE_INFO command
>>> + */
>>> +struct snp_feature_info {
>>> +	u32 eax;
>>> +	u32 ebx;
>>> +	u32 ecx;
>>> +	u32 edx;
>>> +} __packed;
>>> +
>>>  #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>>>  
>>>  /**

Re: [PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command

Posted by Tom Lendacky 1 year, 4 months ago

On 10/2/24 16:40, Kalra, Ashish wrote:
> Hello Tom,
> 
> On 10/2/2024 4:19 PM, Tom Lendacky wrote:
>> On 10/2/24 16:18, Tom Lendacky wrote:
>>> On 9/17/24 15:16, Ashish Kalra wrote:
>>>> From: Ashish Kalra <ashish.kalra@amd.com>
>>>>
>>>> The FEATURE_INFO command provides host and guests a programmatic means
>>>> to learn about the supported features of the currently loaded firmware.
>>>> FEATURE_INFO command leverages the same mechanism as the CPUID instruction.
>>>> Instead of using the CPUID instruction to retrieve Fn8000_0024,
>>>> software can use FEATURE_INFO.
>>>>
>>>> Host/Hypervisor would use the FEATURE_INFO command, while guests would
>>>> actually issue the CPUID instruction.
>>>>
>>>> The hypervisor can provide Fn8000_0024 values to the guest via the CPUID
>>>> page in SNP_LAUNCH_UPDATE. As with all CPUID output recorded in that page,
>>>> the hypervisor can filter Fn8000_0024. The firmware will examine
>>>> Fn8000_0024 and apply its CPUID policy.
>>>>
>>>> During CCP module initialization, after firmware update, the SNP
>>>> platform status and feature information from CPUID 0x8000_0024,
>>>> sub-function 0, are cached in the sev_device structure.
>>>>
>>>> Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
>>>> ---
>>>>  drivers/crypto/ccp/sev-dev.c | 47 ++++++++++++++++++++++++++++++++++++
>>>>  drivers/crypto/ccp/sev-dev.h |  3 +++
>>>>  include/linux/psp-sev.h      | 29 ++++++++++++++++++++++
>>>>  3 files changed, 79 insertions(+)
>>>>
>>>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>>>> index af018afd9cd7..564daf748293 100644
>>>> --- a/drivers/crypto/ccp/sev-dev.c
>>>> +++ b/drivers/crypto/ccp/sev-dev.c
>>>> @@ -223,6 +223,7 @@ static int sev_cmd_buffer_len(int cmd)
>>>>  	case SEV_CMD_SNP_GUEST_REQUEST:		return sizeof(struct sev_data_snp_guest_request);
>>>>  	case SEV_CMD_SNP_CONFIG:		return sizeof(struct sev_user_data_snp_config);
>>>>  	case SEV_CMD_SNP_COMMIT:		return sizeof(struct sev_data_snp_commit);
>>>> +	case SEV_CMD_SNP_FEATURE_INFO:		return sizeof(struct snp_feature_info);
>>>>  	default:				return 0;
>>>>  	}
>>>>  
>>>> @@ -1063,6 +1064,50 @@ static void snp_set_hsave_pa(void *arg)
>>>>  	wrmsrl(MSR_VM_HSAVE_PA, 0);
>>>>  }
>>>>  
>>>> +static void snp_get_platform_data(void)
>>>> +{
>>>> +	struct sev_device *sev = psp_master->sev_data;
>>>> +	struct sev_data_snp_feature_info snp_feat_info;
>>>> +	struct snp_feature_info *feat_info;
>>>> +	struct sev_data_snp_addr buf;
>>>> +	int error = 0, rc;
>>>> +
>>>> +	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
>>>> +		return;
>>>> +
>>>> +	/*
>>>> +	 * The output buffer must be firmware page if SEV-SNP is
>>>> +	 * initialized.
>>> This comment is a little confusing relative to the "if" check that is
>>> performed. Add some more detail about what this check is for.
>>>
>>> But... would this ever need to be called after SNP_INIT? Would we want
>>> to call this again after, say, a DOWNLOAD_FIRMWARE command?
>> Although, as I hit send I realized that we only do DOWNLOAD_FIRMWARE
>> before SNP is initialized (currently).
> 
> We do have DOWNLOAD_FIRMWARE_EX support coming up which can/will happen after SNP_INIT, but there we can still use SEV's PLATFORM_DATA command to get (updated) SEV/SNP firmware version.

But you probably also want to get updated platform data, too. So I would
think you would want to be able to call this routine again, post SNP_INIT.

Thanks,
Tom

> 
> Thanks, Ashish
> 
>>
>> Thanks,
>> Tom
>>
>>> Thanks,
>>> Tom
>>>
>>>> +	 */
>>>> +	if (sev->snp_initialized)
>>>> +		return;
>>>> +
>>>> +	buf.address = __psp_pa(&sev->snp_plat_status);
>>>> +	rc = __sev_do_cmd_locked(SEV_CMD_SNP_PLATFORM_STATUS, &buf, &error);
>>>> +
>>>> +	/*
>>>> +	 * Do feature discovery of the currently loaded firmware,
>>>> +	 * and cache feature information from CPUID 0x8000_0024,
>>>> +	 * sub-function 0.
>>>> +	 */
>>>> +	if (!rc && sev->snp_plat_status.feature_info) {
>>>> +		/*
>>>> +		 * Use dynamically allocated structure for the SNP_FEATURE_INFO
>>>> +		 * command to handle any alignment and page boundary check
>>>> +		 * requirements.
>>>> +		 */
>>>> +		feat_info = kzalloc(sizeof(*feat_info), GFP_KERNEL);
>>>> +		snp_feat_info.length = sizeof(snp_feat_info);
>>>> +		snp_feat_info.ecx_in = 0;
>>>> +		snp_feat_info.feature_info_paddr = __psp_pa(feat_info);
>>>> +
>>>> +		rc = __sev_do_cmd_locked(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, &error);
>>>> +		if (!rc)
>>>> +			sev->feat_info = *feat_info;
>>>> +		kfree(feat_info);
>>>> +	}
>>>> +}
>>>> +
>>>>  static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
>>>>  {
>>>>  	struct sev_data_range_list *range_list = arg;
>>>> @@ -2415,6 +2460,8 @@ void sev_pci_init(void)
>>>>  			 api_major, api_minor, build,
>>>>  			 sev->api_major, sev->api_minor, sev->build);
>>>>  
>>>> +	snp_get_platform_data();
>>>> +
>>>>  	/* Initialize the platform */
>>>>  	args.probe = true;
>>>>  	rc = sev_platform_init(&args);
>>>> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
>>>> index 3e4e5574e88a..1c1a51e52d2b 100644
>>>> --- a/drivers/crypto/ccp/sev-dev.h
>>>> +++ b/drivers/crypto/ccp/sev-dev.h
>>>> @@ -57,6 +57,9 @@ struct sev_device {
>>>>  	bool cmd_buf_backup_active;
>>>>  
>>>>  	bool snp_initialized;
>>>> +
>>>> +	struct sev_user_data_snp_status snp_plat_status;
>>>> +	struct snp_feature_info feat_info;
>>>>  };
>>>>  
>>>>  int sev_dev_init(struct psp_device *psp);
>>>> diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
>>>> index 903ddfea8585..6068a89839e1 100644
>>>> --- a/include/linux/psp-sev.h
>>>> +++ b/include/linux/psp-sev.h
>>>> @@ -107,6 +107,7 @@ enum sev_cmd {
>>>>  	SEV_CMD_SNP_DOWNLOAD_FIRMWARE_EX = 0x0CA,
>>>>  	SEV_CMD_SNP_COMMIT		= 0x0CB,
>>>>  	SEV_CMD_SNP_VLEK_LOAD		= 0x0CD,
>>>> +	SEV_CMD_SNP_FEATURE_INFO	= 0x0CE,
>>>>  
>>>>  	SEV_CMD_MAX,
>>>>  };
>>>> @@ -812,6 +813,34 @@ struct sev_data_snp_commit {
>>>>  	u32 len;
>>>>  } __packed;
>>>>  
>>>> +/**
>>>> + * struct sev_data_snp_feature_info - SEV_SNP_FEATURE_INFO structure
>>>> + *
>>>> + * @length: len of the command buffer read by the PSP
>>>> + * @ecx_in: subfunction index
>>>> + * @feature_info_paddr : SPA of the FEATURE_INFO structure
>>>> + */
>>>> +struct sev_data_snp_feature_info {
>>>> +	u32 length;
>>>> +	u32 ecx_in;
>>>> +	u64 feature_info_paddr;
>>>> +} __packed;
>>>> +
>>>> +/**
>>>> + * struct feature_info - FEATURE_INFO structure
>>>> + *
>>>> + * @eax: output of SNP_FEATURE_INFO command
>>>> + * @ebx: output of SNP_FEATURE_INFO command
>>>> + * @ecx: output of SNP_FEATURE_INFO command
>>>> + * #edx: output of SNP_FEATURE_INFO command
>>>> + */
>>>> +struct snp_feature_info {
>>>> +	u32 eax;
>>>> +	u32 ebx;
>>>> +	u32 ecx;
>>>> +	u32 edx;
>>>> +} __packed;
>>>> +
>>>>  #ifdef CONFIG_CRYPTO_DEV_SP_PSP
>>>>  
>>>>  /**

[PATCH v2 1/3] crypto: ccp: New bit-field definitions for SNP_PLATFORM_STATUS command
[PATCH v2 2/3] crypto: ccp: Add support for SNP_FEATURE_INFO command
[PATCH v2 3/3] x86/sev: Add SEV-SNP CipherTextHiding support