Re: [PATCH RESEND v2] target/riscv: Set mstatus_hs.[SD|FS] bits if Clean and V=1 in mark_fs_dirty()

[Richard Henderson]

On 9/17/21 2:31 AM, frank.ch...@sifive.com wrote:

From: Frank Chang <frank.ch...@sifive.com>

When V=1, both vsstauts.FS and HS-level sstatus.FS are in effect.
Modifying the floating-point state when V=1 causes both fields to
be set to 3 (Dirty).

However, it's possible that HS-level sstatus.FS is Clean and VS-level
vsstatus.FS is Dirty at the time mark_fs_dirty() is called when V=1.
We can't early return for this case because we still need to set
sstatus.FS to Dirty according to spec.

Signed-off-by: Frank Chang <frank.ch...@sifive.com>
Reviewed-by: Vincent Chen <vincent.c...@sifive.com>
Tested-by: Vincent Chen <vincent.c...@sifive.com>
---
  target/riscv/cpu.h       |  4 ++++
  target/riscv/translate.c | 24 +++++++++++++++---------
  2 files changed, 19 insertions(+), 9 deletions(-)

Reviewed-by: Richard Henderson <richard.hender...@linaro.org>

  static void mark_fs_dirty(DisasContext *ctx)
  {
      TCGv tmp;
-    target_ulong sd;
+    target_ulong sd = is_32bit(ctx) ? MSTATUS32_SD : MSTATUS64_SD;
+
+    if (ctx->virt_enabled && ctx->mstatus_hs_fs != MSTATUS_FS) {
+        /* Remember the stage change for the rest of the TB. */
+        ctx->mstatus_hs_fs = MSTATUS_FS;
+
+        tmp = tcg_temp_new();
+        tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
+        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
+        tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
+        tcg_temp_free(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();

-    sd = is_32bit(ctx) ? MSTATUS32_SD : MSTATUS64_SD;
-
      tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
      tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
      tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus));
-
-    if (ctx->virt_enabled) {
-        tcg_gen_ld_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
-        tcg_gen_ori_tl(tmp, tmp, MSTATUS_FS | sd);
-        tcg_gen_st_tl(tmp, cpu_env, offsetof(CPURISCVState, mstatus_hs));
-    }
      tcg_temp_free(tmp);

While it works, it would be nicer to keep these two cases as similar as 
possible.


r~