crypto: ccp - Add support for SNP_FEATURE_INFO command

The FEATURE_INFO command provides hypervisors with a programmatic means
to learn about the supported features of the currently loaded firmware.
This command mimics the CPUID instruction relative to sub-leaf input and
the four unsigned integer output values. To obtain information
regarding the features present in the currently loaded SEV firmware,
use the SNP_FEATURE_INFO command.

Cache the SNP platform status and feature information from CPUID
0x8000_0024 in the sev_device structure. If SNP is enabled, utilize
this cached SNP platform status for the API major, minor and build
version.

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Reviewed-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: ashkalra

drivers/crypto/ccp/sev-dev.c

@@ -233,6 +233,7 @@ 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 sev_data_snp_feature_info);
 	default:				return 0;
 	}
 
@@ -1073,6 +1074,67 @@ static void snp_set_hsave_pa(void *arg)
 	wrmsrq(MSR_VM_HSAVE_PA, 0);
 }
 
+static int snp_get_platform_data(struct sev_device *sev, int *error)
+{
+	struct sev_data_snp_feature_info snp_feat_info;
+	struct snp_feature_info *feat_info;
+	struct sev_data_snp_addr buf;
+	struct page *page;
+	int rc;
+
+	/*
+	 * This function is expected to be called before SNP is
+	 * initialized.
+	 */
+	if (sev->snp_initialized)
+		return -EINVAL;
+
+	buf.address = __psp_pa(&sev->snp_plat_status);
+	rc = sev_do_cmd(SEV_CMD_SNP_PLATFORM_STATUS, &buf, error);
+	if (rc) {
+		dev_err(sev->dev, "SNP PLATFORM_STATUS command failed, ret = %d, error = %#x\n",
+			rc, *error);
+		return rc;
+	}
+
+	sev->api_major = sev->snp_plat_status.api_major;
+	sev->api_minor = sev->snp_plat_status.api_minor;
+	sev->build = sev->snp_plat_status.build_id;
+
+	/*
+	 * Do feature discovery of the currently loaded firmware,
+	 * and cache feature information from CPUID 0x8000_0024,
+	 * sub-function 0.
+	 */
+	if (!sev->snp_plat_status.feature_info)
+		return 0;
+
+	/*
+	 * Use dynamically allocated structure for the SNP_FEATURE_INFO
+	 * command to ensure structure is 8-byte aligned, and does not
+	 * cross a page boundary.
+	 */
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return -ENOMEM;
+
+	feat_info = page_address(page);
+	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(SEV_CMD_SNP_FEATURE_INFO, &snp_feat_info, error);
+	if (!rc)
+		sev->snp_feat_info_0 = *feat_info;
+	else
+		dev_err(sev->dev, "SNP FEATURE_INFO command failed, ret = %d, error = %#x\n",
+			rc, *error);
+
+	__free_page(page);
+
+	return rc;
+}
+
 static int snp_filter_reserved_mem_regions(struct resource *rs, void *arg)
 {
 	struct sev_data_range_list *range_list = arg;
@@ -1599,6 +1661,16 @@ static int sev_get_api_version(void)
 	struct sev_user_data_status status;
 	int error = 0, ret;
 
+	/*
+	 * Cache SNP platform status and SNP feature information
+	 * if SNP is available.
+	 */
+	if (cc_platform_has(CC_ATTR_HOST_SEV_SNP)) {
+		ret = snp_get_platform_data(sev, &error);
+		if (ret)
+			return 1;
+	}
+
 	ret = sev_platform_status(&status, &error);
 	if (ret) {
 		dev_err(sev->dev,

drivers/crypto/ccp/sev-dev.h

@@ -58,6 +58,9 @@ struct sev_device {
 	bool snp_initialized;
 
 	struct sev_user_data_status sev_plat_status;
+
+	struct sev_user_data_snp_status snp_plat_status;
+	struct snp_feature_info snp_feat_info_0;
 };
 
 int sev_dev_init(struct psp_device *psp);

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,
 };
@@ -814,6 +815,34 @@ 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 : System Physical Address 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
 
 /**