[v8,31/35] RISC-V: Mark mstatus.fs dirty

Commit Message

Michael Clark April 25, 2018, 11:45 p.m. UTC

From: Richard Henderson <[e-mail]>

Modifed from Richard Henderson's patch [1] to integrate
with the new control and status register implementation.

[1] https://lists.nongnu.org/archive/html/qemu-devel/2018-03/msg07034.html

Note: the f* CSRs already mark mstatus.FS dirty using
env->mstatus |= mstatus.FS so the bug in the first
spin of this patch has been fixed in a prior commit.

Cc: Sagar Karandikar <[e-mail]>
Cc: Bastian Koppelmann <[e-mail]>
Cc: Palmer Dabbelt <[e-mail]>
Cc: Alistair Francis <[e-mail]>
Cc: Richard Henderson <[e-mail]>
Signed-off-by: Michael Clark <[e-mail]>

Co-authored-by: Richard Henderson <[e-mail]>
Co-authored-by: Michael Clark <[e-mail]>
---
 target/riscv/csr.c       | 12 ------------
 target/riscv/translate.c | 40 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+), 13 deletions(-)

Patch

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index ecf74a0..e005285 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -325,18 +325,6 @@  static int write_mstatus(CPURISCVState *env, int csrno, target_ulong val)
 
     mstatus = (mstatus & ~mask) | (val & mask);
 
-    /* Note: this is a workaround for an issue where mstatus.FS
-       does not report dirty after floating point operations
-       that modify floating point state. This workaround is
-       technically compliant with the RISC-V Privileged
-       specification as it is legal to return only off, or dirty.
-       at the expense of extra floating point save/restore. */
-
-    /* FP is always dirty or off */
-    if (mstatus & MSTATUS_FS) {
-        mstatus |= MSTATUS_FS;
-    }
-
     int dirty = ((mstatus & MSTATUS_FS) == MSTATUS_FS) |
                 ((mstatus & MSTATUS_XS) == MSTATUS_XS);
     mstatus = set_field(mstatus, MSTATUS_SD, dirty);
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 4180c42..442c8cd 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -659,6 +659,31 @@  static void gen_store(DisasContext *ctx, uint32_t opc, int rs1, int rs2,
     tcg_temp_free(dat);
 }
 
+#ifndef CONFIG_USER_ONLY
+/* The states of mstatus_fs are:
+ * 0 = disabled, 1 = initial, 2 = clean, 3 = dirty
+ * We will have already diagnosed disabled state,
+ * and need to turn initial/clean into dirty.
+ */
+static void mark_fs_dirty(DisasContext *ctx)
+{
+    TCGv tmp;
+    if (ctx->mstatus_fs == MSTATUS_FS) {
+        return;
+    }
+    /* Remember the state change for the rest of the TB.  */
+    ctx->mstatus_fs = MSTATUS_FS;
+
+    tmp = tcg_temp_new();
+    tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
+    tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS);
+    tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
+    tcg_temp_free(tmp);
+}
+#else
+static inline void mark_fs_dirty(DisasContext *ctx) { }
+#endif
+
 static void gen_fp_load(DisasContext *ctx, uint32_t opc, int rd,
         int rs1, target_long imm)
 {
@@ -687,6 +712,8 @@  static void gen_fp_load(DisasContext *ctx, uint32_t opc, int rd,
         break;
     }
     tcg_temp_free(t0);
+
+    mark_fs_dirty(ctx);
 }
 
 static void gen_fp_store(DisasContext *ctx, uint32_t opc, int rs1,
@@ -984,6 +1011,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
                          int rs1, int rs2, int rm)
 {
     TCGv t0 = NULL;
+    bool fp_output = true;
 
     if (ctx->mstatus_fs == 0) {
         goto do_illegal;
@@ -1046,6 +1074,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         }
         gen_set_gpr(rd, t0);
         tcg_temp_free(t0);
+        fp_output = false;
         break;
 
     case OPC_RISC_FCVT_W_S:
@@ -1075,6 +1104,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         }
         gen_set_gpr(rd, t0);
         tcg_temp_free(t0);
+        fp_output = false;
         break;
 
     case OPC_RISC_FCVT_S_W:
@@ -1125,6 +1155,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         }
         gen_set_gpr(rd, t0);
         tcg_temp_free(t0);
+        fp_output = false;
         break;
 
     case OPC_RISC_FMV_S_X:
@@ -1217,6 +1248,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         }
         gen_set_gpr(rd, t0);
         tcg_temp_free(t0);
+        fp_output = false;
         break;
 
     case OPC_RISC_FCVT_W_D:
@@ -1246,6 +1278,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         }
         gen_set_gpr(rd, t0);
         tcg_temp_free(t0);
+        fp_output = false;
         break;
 
     case OPC_RISC_FCVT_D_W:
@@ -1293,6 +1326,7 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
         default:
             goto do_illegal;
         }
+        fp_output = false;
         break;
 
     case OPC_RISC_FMV_D_X:
@@ -1309,7 +1343,11 @@  static void gen_fp_arith(DisasContext *ctx, uint32_t opc, int rd,
             tcg_temp_free(t0);
         }
         gen_exception_illegal(ctx);
-        break;
+        return;
+    }
+
+    if (fp_output) {
+        mark_fs_dirty(ctx);
     }
 }