1 files changed, 40 insertions, 0 deletions
diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 89ba168f4f0f..0003e4416efd 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -645,3 +645,43 @@ void sev_prep_identity_maps(unsigned long top_level_pgt)
 
 	sev_verify_cbit(top_level_pgt);
 }
+
+bool early_is_sevsnp_guest(void)
+{
+	static bool sevsnp;
+
+	if (sevsnp)
+		return true;
+
+	if (!(sev_get_status() & MSR_AMD64_SEV_SNP_ENABLED))
+		return false;
+
+	sevsnp = true;
+
+	if (!snp_vmpl) {
+		unsigned int eax, ebx, ecx, edx;
+
+		/*
+		 * CPUID Fn8000_001F_EAX[28] - SVSM support
+		 */
+		eax = 0x8000001f;
+		ecx = 0;
+		native_cpuid(&eax, &ebx, &ecx, &edx);
+		if (eax & BIT(28)) {
+			struct msr m;
+
+			/* Obtain the address of the calling area to use */
+			boot_rdmsr(MSR_SVSM_CAA, &m);
+			boot_svsm_caa = (void *)m.q;
+			boot_svsm_caa_pa = m.q;
+
+			/*
+			 * The real VMPL level cannot be discovered, but the
+			 * memory acceptance routines make no use of that so
+			 * any non-zero value suffices here.
+			 */
+			snp_vmpl = U8_MAX;
+		}
+	}
+	return true;
+}