[PATCH v4 1/2] powerpc/pseries/svm: Use FW_FEATURE to detect SVM

[Sukadev Bhattiprolu <sukadev@linux.ibm.com>]

Use FW_FEATURE_SVM to detect a secure guest (SVM). This would be
more efficient than calling mfmsr() frequently.

Suggested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
---
 arch/powerpc/include/asm/firmware.h       | 3 ++-
 arch/powerpc/include/asm/svm.h            | 6 +++++-
 arch/powerpc/kernel/paca.c                | 6 +++++-
 arch/powerpc/platforms/pseries/firmware.c | 3 +++
 4 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/firmware.h b/arch/powerpc/include/asm/firmware.h
index b3e214a97f3a..23cffcec8a55 100644
--- a/arch/powerpc/include/asm/firmware.h
+++ b/arch/powerpc/include/asm/firmware.h
@@ -51,6 +51,7 @@
 #define FW_FEATURE_BLOCK_REMOVE ASM_CONST(0x0000001000000000)
 #define FW_FEATURE_PAPR_SCM 	ASM_CONST(0x0000002000000000)
 #define FW_FEATURE_ULTRAVISOR	ASM_CONST(0x0000004000000000)
+#define FW_FEATURE_SVM		ASM_CONST(0x0000008000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -69,7 +70,7 @@ enum {
 		FW_FEATURE_TYPE1_AFFINITY | FW_FEATURE_PRRN |
 		FW_FEATURE_HPT_RESIZE | FW_FEATURE_DRMEM_V2 |
 		FW_FEATURE_DRC_INFO | FW_FEATURE_BLOCK_REMOVE |
-		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR,
+		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR | FW_FEATURE_SVM,
 	FW_FEATURE_PSERIES_ALWAYS = 0,
 	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_POWERNV_ALWAYS = 0,
diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 85580b30aba4..1d056c70fa87 100644
--- a/arch/powerpc/include/asm/svm.h
+++ b/arch/powerpc/include/asm/svm.h
@@ -10,9 +10,13 @@
 
 #ifdef CONFIG_PPC_SVM
 
+/*
+ * Note that this is not usable in early boot - before FW
+ * features were probed
+ */
 static inline bool is_secure_guest(void)
 {
-	return mfmsr() & MSR_S;
+	return firmware_has_feature(FW_FEATURE_SVM);
 }
 
 void dtl_cache_ctor(void *addr);
diff --git a/arch/powerpc/kernel/paca.c b/arch/powerpc/kernel/paca.c
index 949eceb254d8..3cba33a99549 100644
--- a/arch/powerpc/kernel/paca.c
+++ b/arch/powerpc/kernel/paca.c
@@ -120,7 +120,11 @@ static struct lppaca * __init new_lppaca(int cpu, unsigned long limit)
 	if (early_cpu_has_feature(CPU_FTR_HVMODE))
 		return NULL;
 
-	if (is_secure_guest())
+	/*
+	 * Firmware features may not have been probed yet, so check
+	 * MSR rather than FW_FEATURE_SVM in is_secure_guest().
+	 */
+	if (mfmsr() & MSR_S)
 		lp = alloc_shared_lppaca(LPPACA_SIZE, 0x400, limit, cpu);
 	else
 		lp = alloc_paca_data(LPPACA_SIZE, 0x400, limit, cpu);
diff --git a/arch/powerpc/platforms/pseries/firmware.c b/arch/powerpc/platforms/pseries/firmware.c
index d4a8f1702417..c98527fb4937 100644
--- a/arch/powerpc/platforms/pseries/firmware.c
+++ b/arch/powerpc/platforms/pseries/firmware.c
@@ -175,4 +175,7 @@ static int __init probe_fw_features(unsigned long node, const char *uname, int
 void __init pseries_probe_fw_features(void)
 {
 	of_scan_flat_dt(probe_fw_features, NULL);
+
+	if (mfmsr() & MSR_S)
+		powerpc_firmware_features |= FW_FEATURE_SVM;
 }
-- 
2.17.2