Re: [Qemu-devel] [PATCH v1 9/9] target/riscv: Add Zifencei and Zicsr as command line options

[Palmer Dabbelt <palmer@sifive.com>]

On Mon, 17 Jun 2019 18:31:25 PDT (-0700), Alistair Francis wrote:
> For completeness let's add Zifencei and Zicsr as command line options,
> even though they can't be disabled at the moment.
>
> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> ---
>  target/riscv/cpu.c | 9 +++++++++
>  target/riscv/cpu.h | 2 ++
>  2 files changed, 11 insertions(+)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 5af1c9b38c..53cf8607f7 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -409,6 +409,13 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
>          set_misa(env, RVXLEN | target_misa);
>      }
>
> +    if (!cpu->cfg.ext_ifencei) {
> +        warn_report("QEMU does not support disabling Zifencei");
> +    }
> +    if (!cpu->cfg.ext_icsr) {
> +        warn_report("QEMU does not support disabling Zicsr");
> +    }
> +
>      riscv_cpu_register_gdb_regs_for_features(cs);
>
>      qemu_init_vcpu(cs);
> @@ -441,6 +448,8 @@ static Property riscv_cpu_properties[] = {
>      DEFINE_PROP_BOOL("s", RISCVCPU, cfg.ext_s, true),
>      DEFINE_PROP_BOOL("u", RISCVCPU, cfg.ext_u, true),
>      DEFINE_PROP_BOOL("Counters", RISCVCPU, cfg.ext_counters, true),
> +    DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
> +    DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
>      DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec),
>      DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true),
>      DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true),
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 786f620564..b4c212dfcf 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -222,6 +222,8 @@ typedef struct RISCVCPU {
>          bool ext_s;
>          bool ext_u;
>          bool ext_counters;
> +        bool ext_ifencei;
> +        bool ext_icsr;
>
>          char *priv_spec;
>          char *user_spec;

I'd rather just support these, which seems about as hard as emitting a warning.
Disabling Zifencei is particularly useful, as the Linux ABI forbids it so this
way we can run tests that way.  Unless I'm missing something, I think these two
should do it:

From 6d645eb1e8ba4d16431af40bf04e5c165475bf5a Mon Sep 17 00:00:00 2001
From: Palmer Dabbelt <palmer@sifive.com>
Date: Mon, 24 Jun 2019 01:59:05 -0700
Subject: [PATCH 1/2] RISC-V: Add support for the Zifencei extension

fence.i has been split out of the base ISA as part of the ratification
process.  This patch adds a Zifencei argument, which disables the
fence.i instruction.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
---
 target/riscv/cpu.c                      | 1 +
 target/riscv/cpu.h                      | 1 +
 target/riscv/insn_trans/trans_rvi.inc.c | 3 +++
 target/riscv/translate.c                | 3 +++
 4 files changed, 8 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index be90fa7d0808..bbad39a337b3 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -441,6 +441,7 @@ static Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("s", RISCVCPU, cfg.ext_s, true),
     DEFINE_PROP_BOOL("u", RISCVCPU, cfg.ext_u, true),
     DEFINE_PROP_BOOL("Counters", RISCVCPU, cfg.ext_counters, true),
+    DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
     DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec),
     DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true),
     DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true),
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 4d4e0f89e206..ba551cd3082c 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -223,6 +223,7 @@ typedef struct RISCVCPU {
         bool ext_s;
         bool ext_u;
         bool ext_counters;
+        bool ext_ifencei;
 
         char *priv_spec;
         char *user_spec;
diff --git a/target/riscv/insn_trans/trans_rvi.inc.c b/target/riscv/insn_trans/trans_rvi.inc.c
index 6cda078ed6ba..766594ba08ce 100644
--- a/target/riscv/insn_trans/trans_rvi.inc.c
+++ b/target/riscv/insn_trans/trans_rvi.inc.c
@@ -484,6 +484,9 @@ static bool trans_fence(DisasContext *ctx, arg_fence *a)
 
 static bool trans_fence_i(DisasContext *ctx, arg_fence_i *a)
 {
+    if (!ctx->ext_ifencei)
+        return false;
+
     /*
      * FENCE_I is a no-op in QEMU,
      * however we need to end the translation block
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 313c27b70073..8d6ab732588d 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -54,6 +54,7 @@ typedef struct DisasContext {
        to any system register, which includes CSR_FRM, so we do not have
        to reset this known value.  */
     int frm;
+    bool ext_ifencei;
 } DisasContext;
 
 #ifdef TARGET_RISCV64
@@ -752,6 +753,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
 {
     DisasContext *ctx = container_of(dcbase, DisasContext, base);
     CPURISCVState *env = cs->env_ptr;
+    RISCVCPU *cpu = RISCV_CPU(cs);
 
     ctx->pc_succ_insn = ctx->base.pc_first;
     ctx->mem_idx = ctx->base.tb->flags & TB_FLAGS_MMU_MASK;
@@ -759,6 +761,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     ctx->priv_ver = env->priv_ver;
     ctx->misa = env->misa;
     ctx->frm = -1;  /* unknown rounding mode */
+    ctx->ext_ifencei = cpu->cfg.ext_ifencei;
 }
 
 static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)
-- 
2.21.0


From 6d280048f076eb0f28ee0c4454a1ed8b130240cb Mon Sep 17 00:00:00 2001
From: Palmer Dabbelt <palmer@sifive.com>
Date: Mon, 24 Jun 2019 01:59:51 -0700
Subject: [PATCH 2/2] RISC-V: Add support for the Zicsr extension

The various CSR instructions have been split out of the base ISA as part
of the ratification process.  This patch adds a Zicsr argument, which
disables all the CSR instructions.

Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
---
 target/riscv/cpu.c                      |  1 +
 target/riscv/cpu.h                      |  1 +
 target/riscv/insn_trans/trans_rvi.inc.c | 18 ++++++++++++++++++
 target/riscv/translate.c                |  2 ++
 4 files changed, 22 insertions(+)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index bbad39a337b3..915b9e77df33 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -442,6 +442,7 @@ static Property riscv_cpu_properties[] = {
     DEFINE_PROP_BOOL("u", RISCVCPU, cfg.ext_u, true),
     DEFINE_PROP_BOOL("Counters", RISCVCPU, cfg.ext_counters, true),
     DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
+    DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
     DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec),
     DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true),
     DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true),
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index ba551cd3082c..0adb307f3298 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -224,6 +224,7 @@ typedef struct RISCVCPU {
         bool ext_u;
         bool ext_counters;
         bool ext_ifencei;
+        bool ext_icsr;
 
         char *priv_spec;
         char *user_spec;
diff --git a/target/riscv/insn_trans/trans_rvi.inc.c b/target/riscv/insn_trans/trans_rvi.inc.c
index 766594ba08ce..66c5202cc5d6 100644
--- a/target/riscv/insn_trans/trans_rvi.inc.c
+++ b/target/riscv/insn_trans/trans_rvi.inc.c
@@ -524,6 +524,9 @@ static bool trans_fence_i(DisasContext *ctx, arg_fence_i *a)
 
 static bool trans_csrrw(DisasContext *ctx, arg_csrrw *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrw(dest, cpu_env, source1, csr_store);
@@ -533,6 +536,9 @@ static bool trans_csrrw(DisasContext *ctx, arg_csrrw *a)
 
 static bool trans_csrrs(DisasContext *ctx, arg_csrrs *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrs(dest, cpu_env, source1, csr_store, rs1_pass);
@@ -542,6 +548,9 @@ static bool trans_csrrs(DisasContext *ctx, arg_csrrs *a)
 
 static bool trans_csrrc(DisasContext *ctx, arg_csrrc *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrc(dest, cpu_env, source1, csr_store, rs1_pass);
@@ -551,6 +560,9 @@ static bool trans_csrrc(DisasContext *ctx, arg_csrrc *a)
 
 static bool trans_csrrwi(DisasContext *ctx, arg_csrrwi *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrw(dest, cpu_env, rs1_pass, csr_store);
@@ -560,6 +572,9 @@ static bool trans_csrrwi(DisasContext *ctx, arg_csrrwi *a)
 
 static bool trans_csrrsi(DisasContext *ctx, arg_csrrsi *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrs(dest, cpu_env, rs1_pass, csr_store, rs1_pass);
@@ -569,6 +584,9 @@ static bool trans_csrrsi(DisasContext *ctx, arg_csrrsi *a)
 
 static bool trans_csrrci(DisasContext *ctx, arg_csrrci *a)
 {
+    if (!ctx->ext_icsr)
+        return false;
+
     TCGv source1, csr_store, dest, rs1_pass;
     RISCV_OP_CSR_PRE;
     gen_helper_csrrc(dest, cpu_env, rs1_pass, csr_store, rs1_pass);
diff --git a/target/riscv/translate.c b/target/riscv/translate.c
index 8d6ab732588d..be46435b9a7b 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -55,6 +55,7 @@ typedef struct DisasContext {
        to reset this known value.  */
     int frm;
     bool ext_ifencei;
+    bool ext_icsr;
 } DisasContext;
 
 #ifdef TARGET_RISCV64
@@ -762,6 +763,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
     ctx->misa = env->misa;
     ctx->frm = -1;  /* unknown rounding mode */
     ctx->ext_ifencei = cpu->cfg.ext_ifencei;
+    ctx->ext_icsr = cpu->cfg.ext_icsr;
 }
 
 static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)
-- 
2.21.0