///////////////////////////////////////////
// vm64check.sv
//
// Written: David_Harris@hmc.edu 4 November 2022
// Modified: 
//
// Purpose: Check for good upper address bits in RV64 mode
// 
// Documentation: RISC-V System on Chip Design Chapter 8
//
// A component of the CORE-V-WALLY configurable RISC-V project.
// 
// Copyright (C) 2021-23 Harvey Mudd College & Oklahoma State University
//
// SPDX-License-Identifier: Apache-2.0 WITH SHL-2.1
//
// Licensed under the Solderpad Hardware License v 2.1 (the “License”); you may not use this file 
// except in compliance with the License, or, at your option, the Apache License version 2.0. You 
// may obtain a copy of the License at
//
// https://solderpad.org/licenses/SHL-2.1/
//
// Unless required by applicable law or agreed to in writing, any work distributed under the 
// License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
// either express or implied. See the License for the specific language governing permissions 
// and limitations under the License.
////////////////////////////////////////////////////////////////////////////////////////////////

`include "wally-config.vh"

module vm64check (
   input  logic [`SVMODE_BITS-1:0] SATP_MODE,
   input  logic [`XLEN-1:0]        VAdr,
   output logic                    SV39Mode, UpperBitsUnequalPageFault
);

  if (`XLEN==64) begin:rv64
      assign SV39Mode = (SATP_MODE == `SV39);
      // page fault if upper bits aren't all the same
      logic UpperEqual39, UpperEqual48;
      assign UpperEqual39 = &(VAdr[63:38]) | ~|(VAdr[63:38]);
      assign UpperEqual48 = &(VAdr[63:47]) | ~|(VAdr[63:47]); 
      assign UpperBitsUnequalPageFault = SV39Mode ? ~UpperEqual39 : ~UpperEqual48;
  end else begin
      assign SV39Mode = 0;
      assign UpperBitsUnequalPageFault = 0;
  end           
endmodule