spapr: add rtas_st_buffer_direct() helper

This is similar to the existing rtas_st_buffer(), but for cases
where the guest is not expecting a length-encoded byte array.
Namely, for calls where a "work area" buffer is used to pass
around arbitrary fields/data.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

include/hw/ppc/spapr.h

@@ -464,6 +464,13 @@ static inline void rtas_st(target_ulong phys, int n, uint32_t val)
     stl_be_phys(&address_space_memory, ppc64_phys_to_real(phys + 4*n), val);
 }
 
+static inline void rtas_st_buffer_direct(target_ulong phys,
+                                         target_ulong phys_len,
+                                         uint8_t *buffer, uint16_t buffer_len)
+{
+    cpu_physical_memory_write(ppc64_phys_to_real(phys), buffer,
+                              MIN(buffer_len, phys_len));
+}
 
 static inline void rtas_st_buffer(target_ulong phys, target_ulong phys_len,
                                   uint8_t *buffer, uint16_t buffer_len)
@@ -473,8 +480,7 @@ static inline void rtas_st_buffer(target_ulong phys, target_ulong phys_len,
     }
     stw_be_phys(&address_space_memory,
                 ppc64_phys_to_real(phys), buffer_len);
-    cpu_physical_memory_write(ppc64_phys_to_real(phys + 2),
-                              buffer, MIN(buffer_len, phys_len - 2));
+    rtas_st_buffer_direct(phys + 2, phys_len - 2, buffer, buffer_len);
 }
 
 typedef void (*spapr_rtas_fn)(PowerPCCPU *cpu, sPAPREnvironment *spapr,