[PATCH v2 05/13] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Richard Henderson posted 13 patches 1 month, 2 weeks ago
Maintainers: "Alex Bennée" <alex.bennee@linaro.org>, Alistair Francis <alistair.francis@wdc.com>, Bin Meng <bin.meng@windriver.com>, Laurent Vivier <laurent@vivier.eu>, Palmer Dabbelt <palmer@dabbelt.com>

[PATCH v2 05/13] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Posted by Richard Henderson 1 month, 2 weeks ago
Begin adding support for switching XLEN at runtime.  Extract the
effective XLEN from MISA and MSTATUS and store for use during translation.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v2: Force SXL and UXL to valid values.
---
 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(-)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 87248b562a..445ba5b395 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 CONFIG_RISCV32
 #define riscv_cpu_mxl(env)      MXL_RV32
diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 1857670a69..840edd66f8 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 officially undefined,
+         * but invalid settings would result in a tcg assert.
+         */
+        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 422f8ab8d0..7e7bb67d15 100644
--- a/target/riscv/translate.c
+++ b/target/riscv/translate.c
@@ -539,7 +539,6 @@ 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;
@@ -551,6 +550,7 @@ 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;
-- 
2.25.1


Re: [PATCH v2 05/13] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Posted by Alistair Francis 1 month, 1 week ago
On Thu, Oct 14, 2021 at 6:56 AM Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Begin adding support for switching XLEN at runtime.  Extract the
> effective XLEN from MISA and MSTATUS and store for use during translation.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

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

Alistair

> ---
> v2: Force SXL and UXL to valid values.
> ---
>  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(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 87248b562a..445ba5b395 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 CONFIG_RISCV32
>  #define riscv_cpu_mxl(env)      MXL_RV32
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 1857670a69..840edd66f8 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 officially undefined,
> +         * but invalid settings would result in a tcg assert.
> +         */
> +        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 422f8ab8d0..7e7bb67d15 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -539,7 +539,6 @@ 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;
> @@ -551,6 +550,7 @@ 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;
> --
> 2.25.1
>
>

Re: [PATCH v2 05/13] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Posted by LIU Zhiwei 1 month, 1 week ago
On 2021/10/14 上午4:50, Richard Henderson wrote:
> Begin adding support for switching XLEN at runtime.  Extract the
> effective XLEN from MISA and MSTATUS and store for use during translation.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> v2: Force SXL and UXL to valid values.
> ---
>   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(-)
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index 87248b562a..445ba5b395 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 CONFIG_RISCV32
>   #define riscv_cpu_mxl(env)      MXL_RV32
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 1857670a69..840edd66f8 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 officially undefined,
> +         * but invalid settings would result in a tcg assert.
> +         */
> +        env->mstatus = set_field(env->mstatus, MSTATUS64_SXL, env->misa_mxl);
> +        env->mstatus = set_field(env->mstatus, MSTATUS64_UXL, env->misa_mxl);
> +    }

Can you give more explanation about the assert? As the cpu will always 
reset to M mode, I think we can omit the the setting of UXL or SXL.

Thanks,
Zhiwei

>       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 422f8ab8d0..7e7bb67d15 100644
> --- a/target/riscv/translate.c
> +++ b/target/riscv/translate.c
> @@ -539,7 +539,6 @@ 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;
> @@ -551,6 +550,7 @@ 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;

Re: [PATCH v2 05/13] target/riscv: Add MXL/SXL/UXL to TB_FLAGS

Posted by Richard Henderson 1 month, 1 week ago
On 10/14/21 1:20 AM, LIU Zhiwei wrote:
> 
> On 2021/10/14 上午4:50, Richard Henderson wrote:
>> Begin adding support for switching XLEN at runtime.  Extract the
>> effective XLEN from MISA and MSTATUS and store for use during translation.
>>
>> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
>> ---
>> v2: Force SXL and UXL to valid values.
>> ---
>>   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(-)
>>
>> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
>> index 87248b562a..445ba5b395 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 CONFIG_RISCV32
>>   #define riscv_cpu_mxl(env)      MXL_RV32
>> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
>> index 1857670a69..840edd66f8 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 officially undefined,
>> +         * but invalid settings would result in a tcg assert.
>> +         */
>> +        env->mstatus = set_field(env->mstatus, MSTATUS64_SXL, env->misa_mxl);
>> +        env->mstatus = set_field(env->mstatus, MSTATUS64_UXL, env->misa_mxl);
>> +    }
> 
> Can you give more explanation about the assert? As the cpu will always reset to M mode, I 
> think we can omit the the setting of UXL or SXL.

The mstatus csr is WARL, which means that we should always be able to read a valid value. 
  On init, these fields will still be 0, which isn't right.

I guess the assert that I was considering can't really happen, because we'd need to write 
to mstatus to exit M-mode, and write_mstatus will force these fields to the correct value 
(as found by Frederic).

r~