[Skiboot] [RFC PATCH v7 05/12] Add 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 change to switch from r0 to r3 ]
Signed-off-by: Michael Anderson <andmike at linux.ibm.com>
---
 asm/misc.S           | 29 +++++++++++++++++++++++++++++
 include/ultravisor.h | 11 +++++++++++
 2 files changed, 40 insertions(+)

diff --git a/asm/misc.S b/asm/misc.S
index 30f67872..5119304a 100644
--- a/asm/misc.S
+++ b/asm/misc.S
@@ -275,6 +275,8 @@ enter_p9_pm_state:
  * PEF and bring it out of UV mode. All threads will then be running in HV
  * mode and the only way to re-enable UV mode is with a reboot.
  *
+ * Power9 hardware requires [h]srr1 to be set explicitly.
+ *
  * r3 = 1 if primary thread
  *      0 if secondary thread
  */
@@ -327,3 +329,30 @@ enter_uv:
 	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 05edb53e..623b81d4 100644
--- a/include/ultravisor.h
+++ b/include/ultravisor.h
@@ -32,4 +32,15 @@ extern bool uv_present;
 
 void init_uv(void);
 
+/*
+ * ucall: Make an ultracall
+ * @opcode: The ultracall to make
+ * @retbuf: Buffer to store up to 4 return arguments
+ *
+ * This call supports up to 6 arguments and 4 return arguments. Use
+ * UCALL_BUFSIZE to size the return argument buffer.
+ */
+#define UCALL_BUFSIZE 4
+extern long ucall(unsigned long opcode, unsigned long *retbuf, ...);
+
 #endif /* __ULTRAVISOR_H */
-- 
2.21.0