target/riscv: assert argument to set_satp_mode_max_supported is valid

Check that the argument to set_satp_mode_max_supported is valid for
the MXL value of the CPU.  It would be a bug in the CPU definition
if it weren't.

In fact, there is such a bug in riscv_bare_cpu_init(): not just
SV64 is not a valid VM mode for 32-bit CPUs, SV64 is not a
valid VM mode at all, not yet at least.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index d92874b..0f7ce53 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -444,6 +444,8 @@
             cpu->cfg.satp_mode.supported |= (1 << i);
         }
     }
+
+    assert(cpu->cfg.satp_mode.supported & (1 << satp_mode));
 }
 
 /* Set the satp mode to the max supported */
@@ -1497,7 +1499,9 @@
      * satp_mode manually (see set_satp_mode_default()).
      */
 #ifndef CONFIG_USER_ONLY
-    set_satp_mode_max_supported(cpu, VM_1_10_SV64);
+    set_satp_mode_max_supported(RISCV_CPU(obj),
+        riscv_cpu_mxl(&RISCV_CPU(obj)->env) == MXL_RV32 ?
+        VM_1_10_SV32 : VM_1_10_SV57);
 #endif
 }