powerpc/pseries: Introduce option to build secure virtual machines

Introduce CONFIG_PPC_SVM to control support for secure guests and include
Ultravisor-related helpers when it is selected

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190820021326.6884-3-bauerman@linux.ibm.com

arch/powerpc/include/asm/asm-prototypes.h

@@ -36,7 +36,7 @@ void __trace_hcall_entry(unsigned long opcode, unsigned long *args);
 void __trace_hcall_exit(long opcode, long retval, unsigned long *retbuf);
 
 /* Ultravisor */
-#ifdef CONFIG_PPC_POWERNV
+#if defined(CONFIG_PPC_POWERNV) || defined(CONFIG_PPC_SVM)
 long ucall_norets(unsigned long opcode, ...);
 #else
 static inline long ucall_norets(unsigned long opcode, ...)

arch/powerpc/kernel/Makefile

@@ -156,7 +156,9 @@ endif
 
 obj-$(CONFIG_EPAPR_PARAVIRT)	+= epapr_paravirt.o epapr_hcalls.o
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvm_emul.o
-obj-$(CONFIG_PPC_POWERNV)	+= ucall.o
+ifneq ($(CONFIG_PPC_POWERNV)$(CONFIG_PPC_SVM),)
+obj-y				+= ucall.o
+endif
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n

arch/powerpc/platforms/pseries/Kconfig

@@ -145,3 +145,14 @@ config PAPR_SCM
 	tristate "Support for the PAPR Storage Class Memory interface"
 	help
 	  Enable access to hypervisor provided storage class memory.
+
+config PPC_SVM
+	bool "Secure virtual machine (SVM) support for POWER"
+	depends on PPC_PSERIES
+	help
+	 There are certain POWER platforms which support secure guests using
+	 the Protected Execution Facility, with the help of an Ultravisor
+	 executing below the hypervisor layer. This enables support for
+	 those guests.
+
+	 If unsure, say "N".