Previously the mycycle/minstret CSRs and rdcycle/rdinstret
psuedo instructions would return the time as a proxy for an
increasing instruction counter in the absence of having a
precise instruction count. If QEMU is invoked with -icount,
the mcycle/minstret CSRs and rdcycle/rdinstret psuedo
instructions will return the instruction count.

Cc: Sagar Karandikar <sagark@eecs.berkeley.edu>
Cc: Bastian Koppelmann <kbastian@mail.uni-paderborn.de>
Cc: Palmer Dabbelt <palmer@sifive.com>
Cc: Alistair Francis <Alistair.Francis@wdc.com>
Signed-off-by: Michael Clark <mjc@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/op_helper.c | 28 ++++++++++++++++++++++++++--
 target/riscv/translate.c |  2 ++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 7416412b187c..3512462f4fd8 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -434,25 +434,49 @@ target_ulong csr_read_helper(CPURISCVState *env, target_ulong csrno)
     case CSR_INSTRET:
     case CSR_CYCLE:
         if (ctr_ok) {
+#if !defined(CONFIG_USER_ONLY)
+            if (use_icount) {
+                return cpu_get_icount();
+            } else {
+                return cpu_get_host_ticks();
+            }
+#else
             return cpu_get_host_ticks();
+#endif
         }
         break;
 #if defined(TARGET_RISCV32)
     case CSR_INSTRETH:
     case CSR_CYCLEH:
         if (ctr_ok) {
+#if !defined(CONFIG_USER_ONLY)
+            if (use_icount) {
+                return cpu_get_icount() >> 32;
+            } else {
+                return cpu_get_host_ticks() >> 32;
+            }
+#else
             return cpu_get_host_ticks() >> 32;
+#endif
         }
         break;
 #endif
 #ifndef CONFIG_USER_ONLY
     case CSR_MINSTRET:
     case CSR_MCYCLE:
-        return cpu_get_host_ticks();
+        if (use_icount) {
+            return cpu_get_icount();
+        } else {
+            return cpu_get_host_ticks();
+        }
     case CSR_MINSTRETH:
     case CSR_MCYCLEH:
 #if defined(TARGET_RISCV32)
-        return cpu_get_host_ticks() >> 32;
+        if (use_icount) {
+            return cpu_get_icount() >> 32;
+        } else {
+            return cpu_get_host_ticks() >> 32;
+        }
 #endif
         break;
     case CSR_MUCOUNTEREN:
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index c3a029afefd9..c0e6a044d383 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -1390,6 +1390,7 @@ static void gen_system(CPURISCVState *env, DisasContext *ctx, uint32_t opc,
         break;
     default:
         tcg_gen_movi_tl(imm_rs1, rs1);
+        gen_io_start();
         switch (opc) {
         case OPC_RISC_CSRRW:
             gen_helper_csrrw(dest, cpu_env, source1, csr_store);
@@ -1413,6 +1414,7 @@ static void gen_system(CPURISCVState *env, DisasContext *ctx, uint32_t opc,
             gen_exception_illegal(ctx);
             return;
         }
+        gen_io_end();
         gen_set_gpr(rd, dest);
         /* end tb since we may be changing priv modes, to get mmu_index right */
         tcg_gen_movi_tl(cpu_pc, ctx->next_pc);
-- 
2.7.0