Merge pull request openhwgroup#138 from msfschaffner/ariane_next

Fix mismatches in virtual address checking logic (this fixes openhwgroup#136).

- Instr/ld/st must only throw access faults when virtual memory translation is enabled
- Correct tested bit slice from [63:39] to [63:38]
- Fixes openhwgroup#136

src/lsu.sv

@@ -329,19 +329,19 @@ module lsu #(
             end
         end
 
-        // check that all bits in the address >= 39 are equal
-        if (!((&lsu_ctrl.vaddr[63:39]) == 1'b1 || (|lsu_ctrl.vaddr[63:39]) == 1'b0)) begin
+        // we work with SV39, so if VM is enabled, check that all bits [63:38] are equal
+        if (en_ld_st_translation_i && !((&lsu_ctrl.vaddr[63:38]) == 1'b1 || (|lsu_ctrl.vaddr[63:38]) == 1'b0)) begin
 
             if (lsu_ctrl.fu == LOAD) begin
                 misaligned_exception = {
-                    riscv::LOAD_PAGE_FAULT,
+                    riscv::LD_ACCESS_FAULT,
                     lsu_ctrl.vaddr,
                     1'b1
                 };
 
             end else if (lsu_ctrl.fu == STORE) begin
                 misaligned_exception = {
-                    riscv::STORE_PAGE_FAULT,
+                    riscv::ST_ACCESS_FAULT,
                     lsu_ctrl.vaddr,
                     1'b1
                 };

src/mmu.sv

@@ -191,15 +191,16 @@ module mmu #(
         iaccess_err   = icache_areq_i.fetch_req && (((priv_lvl_i == riscv::PRIV_LVL_U) && ~itlb_content.u)
                                                  || ((priv_lvl_i == riscv::PRIV_LVL_S) && itlb_content.u));
 
-        // check that the upper-most bits (63-39) are the same, otherwise throw a page fault exception...
-        if (icache_areq_i.fetch_req && !((&icache_areq_i.fetch_vaddr[63:39]) == 1'b1 || (|icache_areq_i.fetch_vaddr[63:39]) == 1'b0)) begin
-            icache_areq_o.fetch_exception = {riscv::INSTR_PAGE_FAULT, icache_areq_i.fetch_vaddr, 1'b1};
-        end
         // MMU enabled: address from TLB, request delayed until hit. Error when TLB
         // hit and no access right or TLB hit and translated address not valid (e.g.
         // AXI decode error), or when PTW performs walk due to ITLB miss and raises
         // an error.
         if (enable_translation_i) begin
+            // we work with SV39, so if VM is enabled, check that all bits [63:38] are equal
+            if (icache_areq_i.fetch_req && !((&icache_areq_i.fetch_vaddr[63:38]) == 1'b1 || (|icache_areq_i.fetch_vaddr[63:38]) == 1'b0)) begin
+                icache_areq_o.fetch_exception = {riscv::INSTR_ACCESS_FAULT, icache_areq_i.fetch_vaddr, 1'b1};
+            end
+
             icache_areq_o.fetch_valid = 1'b0;
 
             // 4K page