powerpc/pseries: Add FW_FEATURE_PLPKS feature flag

Add a firmware feature flag, FW_FEATURE_PLPKS, to indicate availability of
Platform KeyStore related hcalls.

Check this flag in plpks_is_available() and pseries_plpks_init() before
trying to make an hcall.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230224041012.772648-1-ajd@linux.ibm.com

arch/powerpc/include/asm/firmware.h

@@ -56,6 +56,7 @@
 #define FW_FEATURE_FORM2_AFFINITY ASM_CONST(0x0000020000000000)
 #define FW_FEATURE_ENERGY_SCALE_INFO ASM_CONST(0x0000040000000000)
 #define FW_FEATURE_WATCHDOG	ASM_CONST(0x0000080000000000)
+#define FW_FEATURE_PLPKS	ASM_CONST(0x0000100000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -77,7 +78,8 @@ enum {
 		FW_FEATURE_DRC_INFO | FW_FEATURE_BLOCK_REMOVE |
 		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR |
 		FW_FEATURE_RPT_INVALIDATE | FW_FEATURE_FORM2_AFFINITY |
-		FW_FEATURE_ENERGY_SCALE_INFO | FW_FEATURE_WATCHDOG,
+		FW_FEATURE_ENERGY_SCALE_INFO | FW_FEATURE_WATCHDOG |
+		FW_FEATURE_PLPKS,
 	FW_FEATURE_PSERIES_ALWAYS = 0,
 	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_POWERNV_ALWAYS = 0,

arch/powerpc/platforms/pseries/firmware.c

@@ -68,6 +68,7 @@ hypertas_fw_features_table[] = {
 	{FW_FEATURE_RPT_INVALIDATE,	"hcall-rpt-invalidate"},
 	{FW_FEATURE_ENERGY_SCALE_INFO,	"hcall-energy-scale-info"},
 	{FW_FEATURE_WATCHDOG,		"hcall-watchdog"},
+	{FW_FEATURE_PLPKS,		"hcall-pks"},
 };
 
 /* Build up the firmware features bitmask using the contents of

arch/powerpc/platforms/pseries/plpks.c

@@ -378,7 +378,7 @@ bool plpks_is_available(void)
 {
 	int rc;
 
-	if (!firmware_has_feature(FW_FEATURE_LPAR))
+	if (!firmware_has_feature(FW_FEATURE_PLPKS))
 		return false;
 
 	rc = _plpks_get_config();
@@ -690,6 +690,9 @@ static __init int pseries_plpks_init(void)
 {
 	int rc;
 
+	if (!firmware_has_feature(FW_FEATURE_PLPKS))
+		return -ENODEV;
+
 	rc = _plpks_get_config();
 
 	if (rc) {