UXL=SXL=MXL

https://github.com/riscv/riscv-isa-manual/commit/326bec83de23f4d2daf24cfed6b5251748cad632

diff --git a/riscv/encoding.h b/riscv/encoding.h
index 1463801b990291c69d25cf049e87df67e3d7fc53..8ec134596e9497d739897772eba81bd9e9566d31 100644 (file)
--- a/riscv/encoding.h
+++ b/riscv/encoding.h
@@ -23,6 +23,8 @@
 #define MSTATUS_TW          0x00200000
 #define MSTATUS_TSR         0x00400000
 #define MSTATUS32_SD        0x80000000
+#define MSTATUS_UXL         0x0000000300000000
+#define MSTATUS_SXL         0x0000000C00000000
 #define MSTATUS64_SD        0x8000000000000000
 
 #define SSTATUS_UIE         0x00000001
@@ -35,6 +37,7 @@
 #define SSTATUS_SUM         0x00040000
 #define SSTATUS_MXR         0x00080000
 #define SSTATUS32_SD        0x80000000
+#define SSTATUS_UXL         0x0000000300000000
 #define SSTATUS64_SD        0x8000000000000000
 
 #define DCSR_XDEBUGVER      (3U<<30)

diff --git a/riscv/processor.cc b/riscv/processor.cc
index ab5640e23aaca13ee2013a5ca63304ce042df59a..664b44d7df1fa5f0b7f8ff6e908e81c8edcf67c5 100644 (file)
--- a/riscv/processor.cc
+++ b/riscv/processor.cc
@@ -178,6 +178,15 @@ void processor_t::take_interrupt(reg_t pending_interrupts)
     throw trap_t(((reg_t)1 << (max_xlen-1)) | ctz(enabled_interrupts));
 }
 
+static int xlen_to_uxl(int xlen)
+{
+  if (xlen == 32)
+    return 1;
+  if (xlen == 64)
+    return 2;
+  abort();
+}
+
 void processor_t::set_privilege(reg_t prv)
 {
   assert(prv <= PRV_M);
@@ -300,7 +309,8 @@ void processor_t::set_csr(int which, reg_t val)
       reg_t mask = MSTATUS_SIE | MSTATUS_SPIE | MSTATUS_MIE | MSTATUS_MPIE
                  | MSTATUS_SPP | MSTATUS_FS | MSTATUS_MPRV | MSTATUS_SUM
                  | MSTATUS_MPP | MSTATUS_MXR | MSTATUS_TW | MSTATUS_TVM
-                 | MSTATUS_TSR | (ext ? MSTATUS_XS : 0);
+                 | MSTATUS_TSR | MSTATUS_UXL | MSTATUS_SXL |
+                 (ext ? MSTATUS_XS : 0);
 
       state.mstatus = (state.mstatus & ~mask) | (val & mask);
 
@@ -311,8 +321,9 @@ void processor_t::set_csr(int which, reg_t val)
       else
         state.mstatus = set_field(state.mstatus, MSTATUS64_SD, dirty);
 
-      // spike supports the notion of xlen < max_xlen, but current priv spec
-      // doesn't provide a mechanism to run RV32 software on an RV64 machine
+      state.mstatus = set_field(state.mstatus, MSTATUS_UXL, xlen_to_uxl(max_xlen));
+      state.mstatus = set_field(state.mstatus, MSTATUS_SXL, xlen_to_uxl(max_xlen));
+      // U-XLEN == S-XLEN == M-XLEN
       xlen = max_xlen;
       break;
     }
@@ -513,7 +524,7 @@ reg_t processor_t::get_csr(int which)
     case CSR_MCOUNTEREN: return state.mcounteren;
     case CSR_SSTATUS: {
       reg_t mask = SSTATUS_SIE | SSTATUS_SPIE | SSTATUS_SPP | SSTATUS_FS
-                 | SSTATUS_XS | SSTATUS_SUM;
+                 | SSTATUS_XS | SSTATUS_SUM | SSTATUS_UXL;
       reg_t sstatus = state.mstatus & mask;
       if ((sstatus & SSTATUS_FS) == SSTATUS_FS ||
           (sstatus & SSTATUS_XS) == SSTATUS_XS)