[RFC PATCH v2 3/4] crypto: ccp - Add an API to return the supported SEV-SNP policy bits

[Tom Lendacky <thomas.lendacky@amd.com>]

Supported policy bits are dependent on the level of SEV firmware that is
currently running. Create an API to return the supported policy bits for
a given level of firmware. KVM will AND that value with the KVM supported
policy bits to generate the actual supported policy bits.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kvm/svm/sev.c       |  3 ++-
 drivers/crypto/ccp/sev-dev.c | 37 ++++++++++++++++++++++++++++++++++++
 include/linux/psp-sev.h      | 20 +++++++++++++++++++
 3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e63f2ee57204..f77da22200fb 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3083,7 +3083,8 @@ void __init sev_hardware_setup(void)
 			sev_snp_supported = is_sev_snp_initialized();
 
 		if (sev_snp_supported) {
-			snp_supported_policy_bits = KVM_SNP_POLICY_MASK_VALID;
+			snp_supported_policy_bits = sev_get_snp_policy_bits();
+			snp_supported_policy_bits &= KVM_SNP_POLICY_MASK_VALID;
 			nr_ciphertext_hiding_asids = init_args.max_snp_asid;
 		}
 
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 334405461657..d4159cec12a0 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2583,6 +2583,43 @@ void sev_platform_shutdown(void)
 }
 EXPORT_SYMBOL_GPL(sev_platform_shutdown);
 
+u64 sev_get_snp_policy_bits(void)
+{
+	struct psp_device *psp = psp_master;
+	struct sev_device *sev;
+	u64 policy_bits;
+
+	if (!cc_platform_has(CC_ATTR_HOST_SEV_SNP))
+		return 0;
+
+	if (!psp || !psp->sev_data)
+		return 0;
+
+	sev = psp->sev_data;
+
+	policy_bits = SNP_POLICY_MASK_BASE;
+
+	if (sev->snp_plat_status.feature_info) {
+		if (sev->snp_feat_info_0.ecx & SNP_RAPL_DISABLE_SUPPORTED)
+			policy_bits |= SNP_POLICY_MASK_RAPL_DIS;
+
+		if (sev->snp_feat_info_0.ecx & SNP_CIPHER_TEXT_HIDING_SUPPORTED)
+			policy_bits |= SNP_POLICY_MASK_CIPHERTEXT_HIDING_DRAM;
+
+		if (sev->snp_feat_info_0.ecx & SNP_AES_256_XTS_POLICY_SUPPORTED)
+			policy_bits |= SNP_POLICY_MASK_MEM_AES_256_XTS;
+
+		if (sev->snp_feat_info_0.ecx & SNP_CXL_ALLOW_POLICY_SUPPORTED)
+			policy_bits |= SNP_POLICY_MASK_CXL_ALLOW;
+
+		if (sev_version_greater_or_equal(1, 58))
+			policy_bits |= SNP_POLICY_MASK_PAGE_SWAP_DISABLE;
+	}
+
+	return policy_bits;
+}
+EXPORT_SYMBOL_GPL(sev_get_snp_policy_bits);
+
 void sev_dev_destroy(struct psp_device *psp)
 {
 	struct sev_device *sev = psp->sev_data;
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 27c92543bf38..1b4c68ec5c65 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -32,6 +32,20 @@
 #define SNP_POLICY_MASK_MIGRATE_MA		BIT_ULL(18)
 #define SNP_POLICY_MASK_DEBUG			BIT_ULL(19)
 #define SNP_POLICY_MASK_SINGLE_SOCKET		BIT_ULL(20)
+#define SNP_POLICY_MASK_CXL_ALLOW		BIT_ULL(21)
+#define SNP_POLICY_MASK_MEM_AES_256_XTS		BIT_ULL(22)
+#define SNP_POLICY_MASK_RAPL_DIS		BIT_ULL(23)
+#define SNP_POLICY_MASK_CIPHERTEXT_HIDING_DRAM	BIT_ULL(24)
+#define SNP_POLICY_MASK_PAGE_SWAP_DISABLE	BIT_ULL(25)
+
+/* Base SEV-SNP policy bitmask for minimum supported SEV firmware version */
+#define SNP_POLICY_MASK_BASE	(SNP_POLICY_MASK_API_MINOR		| \
+				 SNP_POLICY_MASK_API_MAJOR		| \
+				 SNP_POLICY_MASK_SMT			| \
+				 SNP_POLICY_MASK_RSVD_MBO		| \
+				 SNP_POLICY_MASK_MIGRATE_MA		| \
+				 SNP_POLICY_MASK_DEBUG			| \
+				 SNP_POLICY_MASK_SINGLE_SOCKET)
 
 #define SEV_FW_BLOB_MAX_SIZE	0x4000	/* 16KB */
 
@@ -868,7 +882,10 @@ struct snp_feature_info {
 	u32 edx;
 } __packed;
 
+#define SNP_RAPL_DISABLE_SUPPORTED		BIT(2)
 #define SNP_CIPHER_TEXT_HIDING_SUPPORTED	BIT(3)
+#define SNP_AES_256_XTS_POLICY_SUPPORTED	BIT(4)
+#define SNP_CXL_ALLOW_POLICY_SUPPORTED		BIT(5)
 
 #ifdef CONFIG_CRYPTO_DEV_SP_PSP
 
@@ -1014,6 +1031,7 @@ void *snp_alloc_firmware_page(gfp_t mask);
 void snp_free_firmware_page(void *addr);
 void sev_platform_shutdown(void);
 bool sev_is_snp_ciphertext_hiding_supported(void);
+u64 sev_get_snp_policy_bits(void);
 
 #else	/* !CONFIG_CRYPTO_DEV_SP_PSP */
 
@@ -1052,6 +1070,8 @@ static inline void sev_platform_shutdown(void) { }
 
 static inline bool sev_is_snp_ciphertext_hiding_supported(void) { return false; }
 
+static inline u64 sev_get_snp_policy_bits(void) { return 0; }
+
 #endif	/* CONFIG_CRYPTO_DEV_SP_PSP */
 
 #endif	/* __PSP_SEV_H__ */
-- 
2.46.2