Re: [Qemu-devel] [PATCH 1/3] spapr: Small fixes to rtas_ibm_get_system_parameter, remove rtas_st_buffer

[Alexey Kardashevskiy]

On 01/16/2016 12:14 PM, David Gibson wrote:
rtas_st_buffer() appears in spapr.h as though it were a widely used helper,
but in fact it is only used for saving data in a format used by
rtas_ibm_get_system_parameter().  We can fold it into that caller just as
simply.
While we're there fix a couple of small defects in
rtas_ibm_get_system_parameter:
   - For the string value SPLPAR_CHARACTERISTICS, it wasn't including the
     terminating \0 in the length which it should according to LoPAPR
     7.3.16.1
   - It now checks that the supplied buffer has at least enough space for
     the length of the returned data, and returns an error if it does not.

Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
---
  hw/ppc/spapr_rtas.c    | 28 ++++++++++++++++++++--------
  include/hw/ppc/spapr.h | 11 -----------
  2 files changed, 20 insertions(+), 19 deletions(-)

diff --git a/hw/ppc/spapr_rtas.c b/hw/ppc/spapr_rtas.c
index 34b12a3..f4fb9ba 100644
--- a/hw/ppc/spapr_rtas.c
+++ b/hw/ppc/spapr_rtas.c
@@ -235,9 +235,15 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu,
                                            uint32_t nret, target_ulong rets)
  {
      target_ulong parameter = rtas_ld(args, 0);
-    target_ulong buffer = rtas_ld(args, 1);
+    target_ulong buffer = ppc64_phys_to_real(rtas_ld(args, 1));
      target_ulong length = rtas_ld(args, 2);
-    target_ulong ret = RTAS_OUT_SUCCESS;
+    void *val;
+    size_t vallen;

Having such temporary variables (val/vallen) tells me that a helper is a 
better solution as this assumes that one word and one buffer will be ever 
enough for all cases but there is already "7.3.16.17 Processor Module 
Information" coming (even though I have not heard from Sukadev for quite 
some time) which is more complicated that this.

May be rtas_st_buffer() is not the best name and it does not have to be 
global so I'd propose making it static and calling it syspar_st().


+
+    if (length < 2) {
+        rtas_st(rets, 0, -9999); /* Parameter error */


#define RTAS_OUT_SYSPAR_PARAM_ERROR -9999
and then
rtas_st(rets, 0, RTAS_OUT_SYSPAR_PARAM_ERROR);

?

In all other places ("rtas_st(\S\+, 0") a macro is used (except just one 
case in spapr_pci.c which needs a fix).


+        return;
+    }

      switch (parameter) {
      case RTAS_SYSPARM_SPLPAR_CHARACTERISTICS: {
@@ -249,24 +255,30 @@ static void rtas_ibm_get_system_parameter(PowerPCCPU *cpu,
                                            current_machine->ram_size / M_BYTE,
                                            smp_cpus,
                                            max_cpus);
-        rtas_st_buffer(buffer, length, (uint8_t *)param_val, 
strlen(param_val));
+        val = param_val;
+        vallen = strlen(param_val) + 1;
          g_free(param_val);
          break;
      }
      case RTAS_SYSPARM_DIAGNOSTICS_RUN_MODE: {
-        uint8_t param_val = DIAGNOSTICS_RUN_MODE_DISABLED;
+        uint8_t diagnostics_run_mode = DIAGNOSTICS_RUN_MODE_DISABLED;

-        rtas_st_buffer(buffer, length, &param_val, sizeof(param_val));
+        val = &diagnostics_run_mode;


I know that any reasonable compiler will keep @diagnostics_run_mode on 
stack till return but it is still not clean...



+        vallen = sizeof(diagnostics_run_mode);
          break;
      }
      case RTAS_SYSPARM_UUID:
-        rtas_st_buffer(buffer, length, qemu_uuid, (qemu_uuid_set ? 16 : 0));
+        val = qemu_uuid;
+        vallen = qemu_uuid_set ? 16 : 0;
          break;
      default:
-        ret = RTAS_OUT_NOT_SUPPORTED;
+        rtas_st(rets, 0, RTAS_OUT_NOT_SUPPORTED);
+        return;
      }

-    rtas_st(rets, 0, ret);
+    stw_be_phys(&address_space_memory, buffer, vallen);
+    cpu_physical_memory_write(buffer + 2, val, MIN(vallen, length - 2));
+    rtas_st(rets, 0, 0); /* Success */


rtas_st(rets, 0, RTAS_OUT_SUCCESS);



  }

  static void rtas_ibm_set_system_parameter(PowerPCCPU *cpu,
diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
index 53af76a..ec9e7ea 100644
--- a/include/hw/ppc/spapr.h
+++ b/include/hw/ppc/spapr.h
@@ -513,17 +513,6 @@ static inline void rtas_st_buffer_direct(target_ulong phys,
                                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)
-{
-    if (phys_len < 2) {
-        return;
-    }
-    stw_be_phys(&address_space_memory,
-                ppc64_phys_to_real(phys), buffer_len);
-    rtas_st_buffer_direct(phys + 2, phys_len - 2, buffer, buffer_len);
-}
-
  typedef void (*spapr_rtas_fn)(PowerPCCPU *cpu, sPAPRMachineState *sm,
                                uint32_t token,
                                uint32_t nargs, target_ulong args,



--
Alexey