diff mbox series

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

Message ID 0f225b9d547694cc473ec14d90d1a821845534c3.1726602374.git.ashish.kalra@amd.com
State New
Headers show
Series Add SEV-SNP CipherTextHiding feature support | expand

Commit Message

Ashish Kalra Sept. 17, 2024, 8:16 p.m. UTC 
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 mbox series

Patch

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
 
 /**