diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 09e605c85de4..594cfa19cbd4 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -661,7 +661,7 @@ static inline void snp_leak_pages(u64 pfn, unsigned int pages)
 {
 	__snp_leak_pages(pfn, pages, true);
 }
-void snp_prepare(void);
+int snp_prepare(void);
 void snp_shutdown(void);
 #else
 static inline bool snp_probe_rmptable_info(void) { return false; }
@@ -679,7 +679,7 @@ static inline void __snp_leak_pages(u64 pfn, unsigned int npages, bool dump_rmp)
 static inline void snp_leak_pages(u64 pfn, unsigned int npages) {}
 static inline void kdump_sev_callback(void) { }
 static inline void snp_fixup_e820_tables(void) {}
-static inline void snp_prepare(void) {}
+static inline int snp_prepare(void) { return -ENODEV; }
 static inline void snp_shutdown(void) {}
 #endif
 
diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c
index 41f76f15caa1..8bcdce98f6dc 100644
--- a/arch/x86/virt/svm/sev.c
+++ b/arch/x86/virt/svm/sev.c
@@ -511,8 +511,9 @@ static void clear_hsave_pa(void *arg)
 	wrmsrq(MSR_VM_HSAVE_PA, 0);
 }
 
-void snp_prepare(void)
+int snp_prepare(void)
 {
+	int ret;
 	u64 val;
 
 	/*
@@ -521,12 +522,20 @@ void snp_prepare(void)
 	 */
 	rdmsrq(MSR_AMD64_SYSCFG, val);
 	if (val & MSR_AMD64_SYSCFG_SNP_EN)
-		return;
+		return 0;
 
 	clear_rmp();
 
 	cpus_read_lock();
 
+	if (!cpumask_equal(cpu_online_mask, cpu_present_mask)) {
+		ret = -EOPNOTSUPP;
+		pr_warn("SNP init failed: not all CPUs online. (%*pbl online <-> %*pbl present masks).\n",
+			cpumask_pr_args(cpu_online_mask),
+			cpumask_pr_args(cpu_present_mask));
+		goto unlock;
+	}
+
 	/*
 	 * MtrrFixDramModEn is not shared between threads on a core,
 	 * therefore it must be set on all CPUs prior to enabling SNP.
@@ -537,7 +546,12 @@ void snp_prepare(void)
 	/* SNP_INIT requires MSR_VM_HSAVE_PA to be cleared on all CPUs. */
 	on_each_cpu(clear_hsave_pa, NULL, 1);
 
+	ret = 0;
+
+unlock:
 	cpus_read_unlock();
+
+	return ret;
 }
 EXPORT_SYMBOL_FOR_MODULES(snp_prepare, "ccp");