diff mbox series

[v4,05/16] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Message ID 20211019000108.3678724-6-richard.henderson@linaro.org
State Superseded
Headers show
Series target/riscv: Rationalize XLEN and operand length | expand

Commit Message

Richard Henderson Oct. 19, 2021, midnight UTC 
Begin adding support for switching XLEN at runtime.  Extract the
effective XLEN from MISA and MSTATUS and store for use during translation.

Reviewed-by: LIU Zhiwei <zhiwei_liu@c-sky.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 target/riscv/cpu.h        |  2 ++
 target/riscv/cpu.c        |  8 ++++++++
 target/riscv/cpu_helper.c | 33 +++++++++++++++++++++++++++++++++
 target/riscv/csr.c        |  3 +++
 target/riscv/translate.c  |  2 +-
 5 files changed, 47 insertions(+), 1 deletion(-)

-- 
2.25.1
diff mbox series

Patch

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index d0e82135a9..c24bc9a039 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -395,6 +395,8 @@  FIELD(TB_FLAGS, VILL, 8, 1)
 /* Is a Hypervisor instruction load/store allowed? */
 FIELD(TB_FLAGS, HLSX, 9, 1)
 FIELD(TB_FLAGS, MSTATUS_HS_FS, 10, 2)
+/* The combination of MXL/SXL/UXL that applies to the current cpu mode. */
+FIELD(TB_FLAGS, XL, 12, 2)
 
 #ifdef TARGET_RISCV32
 #define riscv_cpu_mxl(env)  ((void)(env), MXL_RV32)
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 1857670a69..4e1920d5f0 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -355,6 +355,14 @@  static void riscv_cpu_reset(DeviceState *dev)
     env->misa_mxl = env->misa_mxl_max;
     env->priv = PRV_M;
     env->mstatus &= ~(MSTATUS_MIE | MSTATUS_MPRV);
+    if (env->misa_mxl > MXL_RV32) {
+        /*
+         * The reset status of SXL/UXL is undefined, but mstatus is WARL
+         * and we must ensure that the value after init is valid for read.
+         */
+        env->mstatus = set_field(env->mstatus, MSTATUS64_SXL, env->misa_mxl);
+        env->mstatus = set_field(env->mstatus, MSTATUS64_UXL, env->misa_mxl);
+    }
     env->mcause = 0;
     env->pc = env->resetvec;
     env->two_stage_lookup = false;
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 403f54171d..429afd1f48 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -35,6 +35,37 @@  int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
 #endif
 }
 
+static RISCVMXL cpu_get_xl(CPURISCVState *env)
+{
+#if defined(TARGET_RISCV32)
+    return MXL_RV32;
+#elif defined(CONFIG_USER_ONLY)
+    return MXL_RV64;
+#else
+    RISCVMXL xl = riscv_cpu_mxl(env);
+
+    /*
+     * When emulating a 32-bit-only cpu, use RV32.
+     * When emulating a 64-bit cpu, and MXL has been reduced to RV32,
+     * MSTATUSH doesn't have UXL/SXL, therefore XLEN cannot be widened
+     * back to RV64 for lower privs.
+     */
+    if (xl != MXL_RV32) {
+        switch (env->priv) {
+        case PRV_M:
+            break;
+        case PRV_U:
+            xl = get_field(env->mstatus, MSTATUS64_UXL);
+            break;
+        default: /* PRV_S | PRV_H */
+            xl = get_field(env->mstatus, MSTATUS64_SXL);
+            break;
+        }
+    }
+    return xl;
+#endif
+}
+
 void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
                           target_ulong *cs_base, uint32_t *pflags)
 {
@@ -78,6 +109,8 @@  void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
     }
 #endif
 
+    flags = FIELD_DP32(flags, TB_FLAGS, XL, cpu_get_xl(env));
+
     *pflags = flags;
 }
 
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 9c0753bc8b..c4a479ddd2 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -526,6 +526,9 @@  static RISCVException write_mstatus(CPURISCVState *env, int csrno,
         mstatus = set_field(mstatus, MSTATUS32_SD, dirty);
     } else {
         mstatus = set_field(mstatus, MSTATUS64_SD, dirty);
+        /* SXL and UXL fields are for now read only */
+        mstatus = set_field(mstatus, MSTATUS64_SXL, MXL_RV64);
+        mstatus = set_field(mstatus, MSTATUS64_UXL, MXL_RV64);
     }
     env->mstatus = mstatus;
 
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 66857732e8..f7634c175a 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -514,7 +514,6 @@  static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
 #else
     ctx->virt_enabled = false;
 #endif
-    ctx->xl = env->misa_mxl;
     ctx->misa_ext = env->misa_ext;
     ctx->frm = -1;  /* unknown rounding mode */
     ctx->ext_ifencei = cpu->cfg.ext_ifencei;
@@ -526,6 +525,7 @@  static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     ctx->lmul = FIELD_EX32(tb_flags, TB_FLAGS, LMUL);
     ctx->mlen = 1 << (ctx->sew  + 3 - ctx->lmul);
     ctx->vl_eq_vlmax = FIELD_EX32(tb_flags, TB_FLAGS, VL_EQ_VLMAX);
+    ctx->xl = FIELD_EX32(tb_flags, TB_FLAGS, XL);
     ctx->cs = cs;
     ctx->w = false;
     ctx->ntemp = 0;