[RFC PATCH v2 04/10] KVM: PPC: Ultravisor: Add generic ultravisor call handler

[Claudio Carvalho]

From: Ram Pai <linuxram at us.ibm.com>

Add the ucall() function, which can be used to make ultravisor calls
with varied number of in and out arguments. Ultravisor calls can be made
from the host or guests.

This copies the implementation of plpar_hcall().

Signed-off-by: Ram Pai <linuxram at us.ibm.com>
[Change ucall.S to not save CR, rename and move the headers, build
 ucall.S if CONFIG_PPC_UV set, and add some comments in the code]
Signed-off-by: Claudio Carvalho <cclaudio at linux.ibm.com>
---
 arch/powerpc/include/asm/ultravisor-api.h | 20 +++++++++++++++
 arch/powerpc/include/asm/ultravisor.h     | 25 ++++++++++++++++++
 arch/powerpc/kernel/Makefile              |  2 +-
 arch/powerpc/kernel/ucall.S               | 31 +++++++++++++++++++++++
 arch/powerpc/kernel/ultravisor.c          |  4 +++
 5 files changed, 81 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/include/asm/ultravisor-api.h
 create mode 100644 arch/powerpc/kernel/ucall.S

diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
new file mode 100644
index 000000000000..5f538f33c704
--- /dev/null
+++ b/arch/powerpc/include/asm/ultravisor-api.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Ultravisor calls.
+ *
+ * Copyright 2019, IBM Corporation.
+ *
+ */
+#ifndef _ASM_POWERPC_ULTRAVISOR_API_H
+#define _ASM_POWERPC_ULTRAVISOR_API_H
+
+#include <asm/hvcall.h>
+
+/* Return codes */
+#define U_NOT_AVAILABLE		H_NOT_AVAILABLE
+#define U_SUCCESS		H_SUCCESS
+#define U_FUNCTION		H_FUNCTION
+#define U_PARAMETER		H_PARAMETER
+
+#endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
+
diff --git a/arch/powerpc/include/asm/ultravisor.h b/arch/powerpc/include/asm/ultravisor.h
index e5009b0d84ea..e8abc1bbc194 100644
--- a/arch/powerpc/include/asm/ultravisor.h
+++ b/arch/powerpc/include/asm/ultravisor.h
@@ -8,8 +8,33 @@
 #ifndef _ASM_POWERPC_ULTRAVISOR_H
 #define _ASM_POWERPC_ULTRAVISOR_H
 
+#include <asm/ultravisor-api.h>
+
+#if !defined(__ASSEMBLY__)
+
 /* Internal functions */
 extern int early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
 					 int depth, void *data);
 
+/* API functions */
+#define UCALL_BUFSIZE 4
+/**
+ * ucall: Make a powerpc ultravisor call.
+ * @opcode: The ultravisor call to make.
+ * @retbuf: Buffer to store up to 4 return arguments in.
+ *
+ * This call supports up to 6 arguments and 4 return arguments. Use
+ * UCALL_BUFSIZE to size the return argument buffer.
+ */
+#if defined(CONFIG_PPC_UV)
+long ucall(unsigned long opcode, unsigned long *retbuf, ...);
+#else
+static long ucall(unsigned long opcode, unsigned long *retbuf, ...)
+{
+	return U_NOT_AVAILABLE;
+}
+#endif
+
+#endif /* !__ASSEMBLY__ */
+
 #endif	/* _ASM_POWERPC_ULTRAVISOR_H */
diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
index c8ca219e54bf..43ff4546e469 100644
--- a/arch/powerpc/kernel/Makefile
+++ b/arch/powerpc/kernel/Makefile
@@ -154,7 +154,7 @@ endif
 
 obj-$(CONFIG_EPAPR_PARAVIRT)	+= epapr_paravirt.o epapr_hcalls.o
 obj-$(CONFIG_KVM_GUEST)		+= kvm.o kvm_emul.o
-obj-$(CONFIG_PPC_UV)		+= ultravisor.o
+obj-$(CONFIG_PPC_UV)		+= ultravisor.o ucall.o
 
 # Disable GCOV, KCOV & sanitizers in odd or sensitive code
 GCOV_PROFILE_prom_init.o := n
diff --git a/arch/powerpc/kernel/ucall.S b/arch/powerpc/kernel/ucall.S
new file mode 100644
index 000000000000..ecc88998a13b
--- /dev/null
+++ b/arch/powerpc/kernel/ucall.S
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Generic code to perform an ultravisor call.
+ *
+ * Copyright 2019, IBM Corporation.
+ *
+ */
+#include <asm/ppc_asm.h>
+
+/*
+ * This function is based on the plpar_hcall()
+ */
+_GLOBAL_TOC(ucall)
+	mr	r0,r3
+	std     r4,STK_PARAM(R4)(r1)     /* Save ret buffer */
+	mr	r3,r5
+	mr	r4,r6
+	mr	r5,r7
+	mr	r6,r8
+	mr	r7,r9
+	mr	r8,r10
+
+	sc 2				/* invoke the ultravisor */
+
+	ld	r12,STK_PARAM(R4)(r1)
+	std	r4,  0(r12)
+	std	r5,  8(r12)
+	std	r6, 16(r12)
+	std	r7, 24(r12)
+
+	blr				/* return r3 = status */
diff --git a/arch/powerpc/kernel/ultravisor.c b/arch/powerpc/kernel/ultravisor.c
index ac23835bdf5a..9fbf0804ee4e 100644
--- a/arch/powerpc/kernel/ultravisor.c
+++ b/arch/powerpc/kernel/ultravisor.c
@@ -8,10 +8,14 @@
 #include <linux/init.h>
 #include <linux/printk.h>
 #include <linux/string.h>
+#include <linux/export.h>
 
 #include <asm/ultravisor.h>
 #include <asm/firmware.h>
 
+/* in ucall.S */
+EXPORT_SYMBOL_GPL(ucall);
+
 int __init early_init_dt_scan_ultravisor(unsigned long node, const char *uname,
 					 int depth, void *data)
 {
-- 
2.20.1