[POWERPC] Avoid hypervisor statistics calculation in real mode

kexec invokes plpar_hcall hypervisor call in real mode.  plpar_hcall
refers to per cpu variables for accounting hypervisor statistics.
These variables may not be in the RMO region, so accesses to them
in real mode may result in a data storage exception.

This fixes this problem by using a new plpar_hcall_raw function which
does not update the hypervisor call statistics.  Thanks to Anton for
suggesting this idea.
Signed-off-by: Mohan Kumar M <mohan@in.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/pseries/hvCall.S

@@ -123,6 +123,40 @@ _GLOBAL(plpar_hcall)
 
 	blr				/* return r3 = status */
 
+/*
+ * plpar_hcall_raw can be called in real mode. kexec/kdump need some
+ * hypervisor calls to be executed in real mode. So plpar_hcall_raw
+ * does not access the per cpu hypervisor call statistics variables,
+ * since these variables may not be present in the RMO region.
+ */
+_GLOBAL(plpar_hcall_raw)
+	HMT_MEDIUM
+
+	mfcr	r0
+	stw	r0,8(r1)
+
+	std     r4,STK_PARM(r4)(r1)     /* Save ret buffer */
+
+	mr	r4,r5
+	mr	r5,r6
+	mr	r6,r7
+	mr	r7,r8
+	mr	r8,r9
+	mr	r9,r10
+
+	HVSC				/* invoke the hypervisor */
+
+	ld	r12,STK_PARM(r4)(r1)
+	std	r4,  0(r12)
+	std	r5,  8(r12)
+	std	r6, 16(r12)
+	std	r7, 24(r12)
+
+	lwz	r0,8(r1)
+	mtcrf	0xff,r0
+
+	blr				/* return r3 = status */
+
 _GLOBAL(plpar_hcall9)
 	HMT_MEDIUM
 

arch/powerpc/platforms/pseries/lpar.c

@@ -378,7 +378,7 @@ static void pSeries_lpar_hptab_clear(void)
 
 	/* TODO: Use bulk call */
 	for (i = 0; i < hpte_count; i++)
-		plpar_pte_remove(0, i, 0, &dummy1, &dummy2);
+		plpar_pte_remove_raw(0, i, 0, &dummy1, &dummy2);
 }
 
 /*

arch/powerpc/platforms/pseries/plpar_wrappers.h

@@ -78,6 +78,22 @@ static inline long plpar_pte_remove(unsigned long flags, unsigned long ptex,
 	return rc;
 }
 
+/* plpar_pte_remove_raw can be called in real mode. It calls plpar_hcall_raw */
+static inline long plpar_pte_remove_raw(unsigned long flags, unsigned long ptex,
+		unsigned long avpn, unsigned long *old_pteh_ret,
+		unsigned long *old_ptel_ret)
+{
+	long rc;
+	unsigned long retbuf[PLPAR_HCALL_BUFSIZE];
+
+	rc = plpar_hcall_raw(H_REMOVE, retbuf, flags, ptex, avpn);
+
+	*old_pteh_ret = retbuf[0];
+	*old_ptel_ret = retbuf[1];
+
+	return rc;
+}
+
 static inline long plpar_pte_read(unsigned long flags, unsigned long ptex,
 		unsigned long *old_pteh_ret, unsigned long *old_ptel_ret)
 {

include/asm-powerpc/hvcall.h

@@ -236,6 +236,20 @@ long plpar_hcall_norets(unsigned long opcode, ...);
 #define PLPAR_HCALL_BUFSIZE 4
 long plpar_hcall(unsigned long opcode, unsigned long *retbuf, ...);
 
+/**
+ * plpar_hcall_raw: - Make a hypervisor call without calculating hcall stats
+ * @opcode: The hypervisor 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
+ * PLPAR_HCALL_BUFSIZE to size the return argument buffer.
+ *
+ * Used when phyp interface needs to be called in real mode. Similar to
+ * plpar_hcall, but plpar_hcall_raw works in real mode and does not
+ * calculate hypervisor call statistics.
+ */
+long plpar_hcall_raw(unsigned long opcode, unsigned long *retbuf, ...);
+
 /**
  * plpar_hcall9: - Make a pseries hypervisor call with up to 9 return arguments
  * @opcode: The hypervisor call to make.