Refactor set_privilege to subsume set_virt

This cleans up the code and avoids bugs like #1365.

riscv/insns/dret.h

@@ -1,7 +1,6 @@
 require(STATE.debug_mode);
 set_pc_and_serialize(STATE.dpc->read());
-p->set_privilege(STATE.dcsr->prv);
-p->set_virt(STATE.dcsr->v);
+p->set_privilege(STATE.dcsr->prv, STATE.dcsr->v);
 if (STATE.prv < PRV_M)
   STATE.mstatus->write(STATE.mstatus->read() & ~MSTATUS_MPRV);
 

riscv/insns/mnret.h

@@ -11,5 +11,4 @@ if (prev_prv != PRV_M) {
 }
 s = set_field(s, MNSTATUS_NMIE, 1);
 STATE.mnstatus->write(s);
-p->set_privilege(prev_prv);
-p->set_virt(prev_virt);
+p->set_privilege(prev_prv, prev_virt);

riscv/insns/mret.h

@@ -10,5 +10,4 @@ s = set_field(s, MSTATUS_MPIE, 1);
 s = set_field(s, MSTATUS_MPP, p->extension_enabled('U') ? PRV_U : PRV_M);
 s = set_field(s, MSTATUS_MPV, 0);
 p->put_csr(CSR_MSTATUS, s);
-p->set_privilege(prev_prv);
-p->set_virt(prev_virt);
+p->set_privilege(prev_prv, prev_virt);

riscv/insns/sret.h

@@ -24,5 +24,4 @@ if (!STATE.v) {
 
   STATE.mstatus->write(set_field(STATE.mstatus->read(), MSTATUS_MPRV, 0));
 }
-p->set_privilege(prev_prv);
-p->set_virt(prev_virt);
+p->set_privilege(prev_prv, prev_virt);

riscv/processor.cc

@@ -714,11 +714,13 @@ reg_t processor_t::legalize_privilege(reg_t prv)
   return prv;
 }
 
-void processor_t::set_privilege(reg_t prv)
+void processor_t::set_privilege(reg_t prv, bool virt)
 {
   mmu->flush_tlb();
   state.prev_prv = state.prv;
+  state.prev_v = state.v;
   state.prv = legalize_privilege(prv);
+  state.v = virt && state.prv != PRV_M;
 }
 
 const char* processor_t::get_privilege_string()
@@ -741,31 +743,11 @@ const char* processor_t::get_privilege_string()
   abort();
 }
 
-void processor_t::set_virt(bool virt)
-{
-  reg_t tmp, mask;
-
-  if (state.prv == PRV_M)
-    return;
-
-  /*
-    * Ideally, we should flush TLB here but we don't need it because
-    * set_virt() is always used in conjucter with set_privilege() and
-    * set_privilege() will flush TLB unconditionally.
-    *
-    * The virtualized sstatus register also relies on this TLB flush,
-    * since changing V might change sstatus.MXR and sstatus.SUM.
-    */
-  state.prev_v = state.v;
-  state.v = virt;
-}
-
 void processor_t::enter_debug_mode(uint8_t cause)
 {
   state.debug_mode = true;
   state.dcsr->write_cause_and_prv(cause, state.prv, state.v);
-  set_virt(false);
-  set_privilege(PRV_M);
+  set_privilege(PRV_M, false);
   state.dpc->write(state.pc);
   state.pc = DEBUG_ROM_ENTRY;
   in_wfi = false;
@@ -832,8 +814,7 @@ void processor_t::take_trap(trap_t& t, reg_t epc)
     s = set_field(s, MSTATUS_SPP, state.prv);
     s = set_field(s, MSTATUS_SIE, 0);
     state.sstatus->write(s);
-    set_virt(true);
-    set_privilege(PRV_S);
+    set_privilege(PRV_S, true);
   } else if (state.prv <= PRV_S && bit < max_xlen && ((hsdeleg >> bit) & 1)) {
     // Handle the trap in HS-mode
     reg_t vector = (state.nonvirtual_stvec->read() & 1) && interrupt ? 4 * bit : 0;
@@ -857,8 +838,7 @@ void processor_t::take_trap(trap_t& t, reg_t epc)
       s = set_field(s, HSTATUS_GVA, t.has_gva());
       state.hstatus->write(s);
     }
-    set_virt(false);
-    set_privilege(PRV_S);
+    set_privilege(PRV_S, false);
   } else {
     // Handle the trap in M-mode
     const reg_t vector = (state.mtvec->read() & 1) && interrupt ? 4 * bit : 0;
@@ -882,8 +862,7 @@ void processor_t::take_trap(trap_t& t, reg_t epc)
     s = set_field(s, MSTATUS_GVA, t.has_gva());
     state.mstatus->write(s);
     if (state.mstatush) state.mstatush->write(s >> 32);  // log mstatush change
-    set_virt(false);
-    set_privilege(PRV_M);
+    set_privilege(PRV_M, false);
   }
 }
 

riscv/processor.h

@@ -269,8 +269,7 @@ public:
       throw trap_instruction_address_misaligned(state.v, pc, 0, 0);
   }
   reg_t legalize_privilege(reg_t);
-  void set_privilege(reg_t);
-  void set_virt(bool);
+  void set_privilege(reg_t, bool);
   const char* get_privilege_string();
   void update_histogram(reg_t pc);
   const disassembler_t* get_disassembler() { return disassembler; }