target-ppc: permit linux-user to read PVR

Access to the PVR SPR is normally forbidden from userspace apps.  The
Linux kernel, however, fixes up reads in the appropriate trap handler.
To permit applications that read PVR to run on QEMU, then, we need to
implement the same handling of PVR reads.
Signed-off-by: NNathan Froyd <froydnj@codesourcery.com>
Signed-off-by: Nmalc <av1474@comtv.ru>

target-ppc/translate_init.c

@@ -8903,7 +8903,13 @@ static void init_ppc_proc (CPUPPCState *env, const ppc_def_t *def)
     /* Register SPR common to all PowerPC implementations */
     gen_spr_generic(env);
     spr_register(env, SPR_PVR, "PVR",
-                 SPR_NOACCESS, SPR_NOACCESS,
+                 /* Linux permits userspace to read PVR */
+#if defined(CONFIG_LINUX_USER)
+                 &spr_read_generic,
+#else
+                 SPR_NOACCESS,
+#endif
+                 SPR_NOACCESS,
                  &spr_read_generic, SPR_NOACCESS,
                  def->pvr);
     /* Register SVR if it's defined to anything else than POWERPC_SVR_NONE */