Fix vsstatus.FS misbehavior (#661)

* Simplify Boolean logic

No functional change intended.

* Apply same logic to virtualize sstatus.XS as used for VS and FS

Though this macro does not seem to be used anywhere today.

* Extract common macro to DRY up code

* Dirty both mstatus and vsstatus FP fields

Fixes https://github.com/riscv/riscv-isa-sim/issues/660

riscv/decode.h

@@ -217,9 +217,13 @@ private:
 #define FRS1 READ_FREG(insn.rs1())
 #define FRS2 READ_FREG(insn.rs2())
 #define FRS3 READ_FREG(insn.rs3())
-#define dirty_fp_state (STATE.mstatus |= MSTATUS_FS | (xlen == 64 ? MSTATUS64_SD : MSTATUS32_SD))
-#define dirty_ext_state (STATE.mstatus |= MSTATUS_XS | (xlen == 64 ? MSTATUS64_SD : MSTATUS32_SD))
-#define dirty_vs_state (STATE.mstatus |= MSTATUS_VS | (xlen == 64 ? MSTATUS64_SD : MSTATUS32_SD))
+#define dirty_mstatus(bits) ({ reg_t dirties = (bits) | (xlen == 64 ? MSTATUS64_SD : MSTATUS32_SD); \
+                               STATE.mstatus |= dirties; \
+                               if (STATE.v) STATE.vsstatus |= dirties; \
+                            })
+#define dirty_fp_state  dirty_mstatus(MSTATUS_FS)
+#define dirty_ext_state dirty_mstatus(MSTATUS_XS)
+#define dirty_vs_state  dirty_mstatus(MSTATUS_VS)
 #define DO_WRITE_FREG(reg, value) (STATE.FPR.write(reg, value), dirty_fp_state)
 #define WRITE_FRD(value) WRITE_FREG(insn.rd(), value)
  
@@ -242,10 +246,9 @@ private:
 #define require_extension(s) require(p->supports_extension(s))
 #define require_either_extension(A,B) require(p->supports_extension(A) || p->supports_extension(B));
 #define require_impl(s) require(p->supports_impl(s))
-#define require_fp require((((STATE.mstatus & MSTATUS_FS) != 0) && (STATE.v == 0)) || (((STATE.mstatus & MSTATUS_FS) != 0) && ((STATE.vsstatus & SSTATUS_FS) != 0) && STATE.v))
-#define require_accelerator require((STATE.mstatus & MSTATUS_XS) != 0)
-
-#define require_vector_vs require((((STATE.mstatus & MSTATUS_VS) != 0) && (STATE.v == 0)) || (((STATE.mstatus & MSTATUS_VS) != 0) && ((STATE.vsstatus & SSTATUS_VS) != 0) && STATE.v))
+#define require_fp require(((STATE.mstatus & MSTATUS_FS) != 0) && ((STATE.v == 0) || ((STATE.vsstatus & SSTATUS_FS) != 0)))
+#define require_accelerator require(((STATE.mstatus & MSTATUS_XS) != 0) && ((STATE.v == 0) || ((STATE.vsstatus & SSTATUS_XS) != 0)))
+#define require_vector_vs require(((STATE.mstatus & MSTATUS_VS) != 0) && ((STATE.v == 0) || ((STATE.vsstatus & SSTATUS_VS) != 0)))
 #define require_vector(alu) \
   do { \
     require_vector_vs; \

riscv/processor.cc

@@ -644,34 +644,6 @@ void processor_t::set_virt(bool virt)
      * set_virt() is always used in conjucter with set_privilege() and
      * set_privilege() will flush TLB unconditionally.
      */
-    if (state.v and !virt) {
-      /*
-       * When transitioning from virt-on (VS/VU) to virt-off (HS/M)
-       * we should mark Host extension status (i.e. FS, VS, and XS
-       * bits) as dirty when Guest/VM extension status is dirty and
-       * Host extension status is initial, clean, or dirty.
-       */
-      if ((state.vsstatus & SSTATUS_FS) &&
-          ((state.mstatus & SSTATUS_FS) == SSTATUS_FS)) {
-        state.vsstatus |= SSTATUS_FS;
-      }
-      if (supports_extension('V') &&
-          (state.vsstatus & SSTATUS_VS) &&
-          ((state.mstatus & SSTATUS_VS) == SSTATUS_VS)) {
-        state.vsstatus |= SSTATUS_VS;
-      }
-      if ((state.vsstatus & SSTATUS_XS) &&
-          ((state.mstatus & SSTATUS_XS) == SSTATUS_XS)) {
-        state.vsstatus |= SSTATUS_XS;
-      }
-      /* Update SD bit of Host */
-      state.vsstatus &= (xlen == 64 ? ~SSTATUS64_SD : ~SSTATUS32_SD);
-      if (((state.mstatus & SSTATUS_FS) == SSTATUS_FS) ||
-          ((state.vsstatus & SSTATUS_VS) == SSTATUS_VS) ||
-          ((state.vsstatus & SSTATUS_XS) == SSTATUS_XS)) {
-         state.vsstatus |= (xlen == 64 ? SSTATUS64_SD : SSTATUS32_SD);
-      }
-    }
     mask = SSTATUS_VS_MASK;
     mask |= (supports_extension('V') ? SSTATUS_VS : 0);
     mask |= (xlen == 64 ? SSTATUS64_SD : SSTATUS32_SD);