x86/hyperv: Add sev-snp enlightened guest static key

Introduce static key isolation_type_en_snp for enlightened
sev-snp guest check.
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20230818102919.1318039-2-ltykernel@gmail.com

arch/x86/hyperv/ivm.c

@@ -413,3 +413,14 @@ bool hv_isolation_type_snp(void)
 {
 	return static_branch_unlikely(&isolation_type_snp);
 }
+
+DEFINE_STATIC_KEY_FALSE(isolation_type_en_snp);
+/*
+ * hv_isolation_type_en_snp - Check system runs in the AMD SEV-SNP based
+ * isolation enlightened VM.
+ */
+bool hv_isolation_type_en_snp(void)
+{
+	return static_branch_unlikely(&isolation_type_en_snp);
+}
+

arch/x86/include/asm/mshyperv.h

@@ -26,6 +26,7 @@
 union hv_ghcb;
 
 DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
+DECLARE_STATIC_KEY_FALSE(isolation_type_en_snp);
 
 typedef int (*hyperv_fill_flush_list_func)(
 		struct hv_guest_mapping_flush_list *flush,
@@ -239,6 +240,7 @@ static inline void hv_vtom_init(void) {}
 #endif
 
 extern bool hv_isolation_type_snp(void);
+extern bool hv_isolation_type_en_snp(void);
 
 static inline bool hv_is_synic_reg(unsigned int reg)
 {

arch/x86/kernel/cpu/mshyperv.c

@@ -402,8 +402,12 @@ static void __init ms_hyperv_init_platform(void)
 		pr_info("Hyper-V: Isolation Config: Group A 0x%x, Group B 0x%x\n",
 			ms_hyperv.isolation_config_a, ms_hyperv.isolation_config_b);
 
-		if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
+
+		if (cc_platform_has(CC_ATTR_GUEST_SEV_SNP)) {
+			static_branch_enable(&isolation_type_en_snp);
+		} else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) {
 			static_branch_enable(&isolation_type_snp);
+		}
 	}
 
 	if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
@@ -473,7 +477,8 @@ static void __init ms_hyperv_init_platform(void)
 
 #if IS_ENABLED(CONFIG_HYPERV)
 	if ((hv_get_isolation_type() == HV_ISOLATION_TYPE_VBS) ||
-	    (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP))
+	    ((hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP) &&
+	    ms_hyperv.paravisor_present))
 		hv_vtom_init();
 	/*
 	 * Setup the hook to get control post apic initialization.

drivers/hv/hv_common.c

@@ -502,6 +502,12 @@ bool __weak hv_isolation_type_snp(void)
 }
 EXPORT_SYMBOL_GPL(hv_isolation_type_snp);
 
+bool __weak hv_isolation_type_en_snp(void)
+{
+	return false;
+}
+EXPORT_SYMBOL_GPL(hv_isolation_type_en_snp);
+
 void __weak hv_setup_vmbus_handler(void (*handler)(void))
 {
 }

include/asm-generic/mshyperv.h

@@ -36,15 +36,21 @@ struct ms_hyperv_info {
 	u32 nested_features;
 	u32 max_vp_index;
 	u32 max_lp_index;
-	u32 isolation_config_a;
+	union {
+		u32 isolation_config_a;
+		struct {
+			u32 paravisor_present : 1;
+			u32 reserved_a1 : 31;
+		};
+	};
 	union {
 		u32 isolation_config_b;
 		struct {
 			u32 cvm_type : 4;
-			u32 reserved1 : 1;
+			u32 reserved_b1 : 1;
 			u32 shared_gpa_boundary_active : 1;
 			u32 shared_gpa_boundary_bits : 6;
-			u32 reserved2 : 20;
+			u32 reserved_b2 : 20;
 		};
 	};
 	u64 shared_gpa_boundary;
@@ -58,6 +64,7 @@ extern void * __percpu *hyperv_pcpu_output_arg;
 extern u64 hv_do_hypercall(u64 control, void *inputaddr, void *outputaddr);
 extern u64 hv_do_fast_hypercall8(u16 control, u64 input8);
 extern bool hv_isolation_type_snp(void);
+extern bool hv_isolation_type_en_snp(void);
 
 /* Helper functions that provide a consistent pattern for checking Hyper-V hypercall status. */
 static inline int hv_result(u64 status)