[Skiboot] [RFC PATCH 6/8] pef: ultra-call support for skiboot

[Ryan Grimm]

From: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>

A new type of system call called the ultra call is used to get the
services of the ultravisor. This ultracall support is needed in skiboot
to access the xscoms which are in the secure memory area.

Signed-off-by: Madhavan Srinivasan <maddy at linux.vnet.ibm.com>
Signed-off-by: Santosh Sivaraj <santosh at fossix.org>
[ andmike: ABI hange to switch from r0 to r3 ]
Signed-off-by: Michael Anderson <andmike at linux.ibm.com>
[ grimm: Comments to start_uv for register usage ]
Signed-off-by: Ryan Grimm <grimm at linux.ibm.com>
---
 asm/head.S           | 34 +++++++++++++++++++++++++++++++++-
 include/ultravisor.h |  1 +
 2 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/asm/head.S b/asm/head.S
index 18ce3044..f8808b08 100644
--- a/asm/head.S
+++ b/asm/head.S
@@ -1066,6 +1066,11 @@ start_kernel_secondary:
 	mfspr	%r3,SPR_PIR
 	bctr
 
+/* start_uv register usage:
+ *
+ *  r3 is base address of UV
+ *  r4 is ptr to struct uv_opal
+ */
 .global start_uv
 start_uv:
 	mflr    %r0
@@ -1083,7 +1088,34 @@ start_uv:
 	addi    %r7,%r5,1
 	li      %r4,0
 	li      %r5,0
-	bctrl
+	bctrl   /* branch to UV here */
 	ld      %r0,16(%r1)
 	mtlr    %r0
 	blr
+
+.global ucall
+ucall:
+	mflr	%r0
+	stdu	%r1,-STACK_FRAMESIZE(%r1)
+	std	%r0,STACK_LR(%r1)
+	mfcr    %r0
+	stw     %r0,STACK_CR(%r1)
+	std     %r4,STACK_GPR4(%r1)	/* Save ret buffer */
+	mr      %r4,%r5
+	mr      %r5,%r6
+	mr      %r6,%r7
+	mr      %r7,%r8
+	mr      %r8,%r9
+	mr      %r9,%r10
+	sc	2			/* invoke the ultravisor */
+	ld      %r12,STACK_GPR4(%r1)
+	std     %r4,  0(%r12)
+	std     %r5,  8(%r12)
+	std     %r6, 16(%r12)
+	std     %r7, 24(%r12)
+	lwz	%r0,STACK_CR(%r1)
+	mtcrf	0xff,%r0
+	ld	%r0,STACK_LR(%r1)
+	mtlr	%r0
+	addi	%r1,%r1,STACK_FRAMESIZE
+	blr				/* return r3 = status */
diff --git a/include/ultravisor.h b/include/ultravisor.h
index 976b6323..3fc2ecd9 100644
--- a/include/ultravisor.h
+++ b/include/ultravisor.h
@@ -36,5 +36,6 @@ extern void uv_preload_image(void);
 extern void uv_decompress_image(void);
 extern void init_uv(void);
 extern int start_ultravisor(void);
+extern long ucall(unsigned long opcode, unsigned long *retbuf, ...);
 
 #endif /* __ULTRAVISOR_H */
-- 
2.21.0