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Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx
From: |
Wu, Fei |
Subject: |
Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx |
Date: |
Fri, 24 Mar 2023 09:02:44 +0800 |
User-agent: |
Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 |
On 3/23/2023 11:53 PM, Richard Henderson wrote:
> On 3/22/23 19:44, Fei Wu wrote:
>> Currently it's assumed the 2 low bits of mmu_idx map to privilege mode,
>> this assumption won't last as we are about to add more mmu_idx.
>>
>> Signed-off-by: Fei Wu <fei2.wu@intel.com>
>> ---
>> target/riscv/cpu.h | 1 -
>> target/riscv/cpu_helper.c | 2 +-
>> target/riscv/insn_trans/trans_privileged.c.inc | 2 +-
>> target/riscv/insn_trans/trans_xthead.c.inc | 7 +------
>> target/riscv/translate.c | 3 +++
>> 5 files changed, 6 insertions(+), 9 deletions(-)
>>
>> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
>> index 638e47c75a..66f7e3d1ba 100644
>> --- a/target/riscv/cpu.h
>> +++ b/target/riscv/cpu.h
>> @@ -623,7 +623,6 @@ G_NORETURN void
>> riscv_raise_exception(CPURISCVState *env,
>> target_ulong riscv_cpu_get_fflags(CPURISCVState *env);
>> void riscv_cpu_set_fflags(CPURISCVState *env, target_ulong);
>> -#define TB_FLAGS_PRIV_MMU_MASK 3
>> #define TB_FLAGS_PRIV_HYP_ACCESS_MASK (1 << 2)
>> #define TB_FLAGS_MSTATUS_FS MSTATUS_FS
>> #define TB_FLAGS_MSTATUS_VS MSTATUS_VS
>> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
>> index f88c503cf4..76e1b0100e 100644
>> --- a/target/riscv/cpu_helper.c
>> +++ b/target/riscv/cpu_helper.c
>> @@ -762,7 +762,7 @@ static int get_physical_address(CPURISCVState
>> *env, hwaddr *physical,
>> * (riscv_cpu_do_interrupt) is correct */
>> MemTxResult res;
>> MemTxAttrs attrs = MEMTXATTRS_UNSPECIFIED;
>> - int mode = mmu_idx & TB_FLAGS_PRIV_MMU_MASK;
>> + int mode = env->priv;
>
> This is incorrect. You must map back from mmu_idx to priv.
> Recall the semantics of MPRV.
>
The following code (~20 lines below) takes MPRV into consideration:
if (riscv_cpu_two_stage_lookup(mmu_idx)) {
mode = get_field(env->hstatus, HSTATUS_SPVP);
} else if (mode == PRV_M && access_type != MMU_INST_FETCH) {
if (get_field(env->mstatus, MSTATUS_MPRV)) {
mode = get_field(env->mstatus, MSTATUS_MPP);
}
}
I think it's the same logic as the original one.
>> diff --git a/target/riscv/insn_trans/trans_xthead.c.inc
>> b/target/riscv/insn_trans/trans_xthead.c.inc
>> index df504c3f2c..adfb53cb4c 100644
>> --- a/target/riscv/insn_trans/trans_xthead.c.inc
>> +++ b/target/riscv/insn_trans/trans_xthead.c.inc
>> @@ -265,12 +265,7 @@ static bool trans_th_tst(DisasContext *ctx,
>> arg_th_tst *a)
>> static inline int priv_level(DisasContext *ctx)
>> {
>> -#ifdef CONFIG_USER_ONLY
>> - return PRV_U;
>> -#else
>> - /* Priv level is part of mem_idx. */
>> - return ctx->mem_idx & TB_FLAGS_PRIV_MMU_MASK;
>> -#endif
>> + return ctx->priv;
>> }
>
> I guess we aren't expecting optimization to remove dead system code?
> That would be the only reason to keep the ifdef.
>
> This function should be hoisted to translate.c, or simply replaced by
> the field access.
>
I only want to replace mem_idx to priv here, Zhiwei might decide how to
adjust the code further.
Thanks,
Fei.
>> @@ -1162,8 +1163,10 @@ static void
>> riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs)
>> } else {
>> ctx->virt_enabled = false;
>> }
>> + ctx->priv = env->priv;
>
> Incorrect, as Zhiwei pointed out.
> I gave you the changes required to TB_FLAGS...
>
>
> r~
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, (continued)
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, LIU Zhiwei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Wu, Fei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Wu, Fei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, LIU Zhiwei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Wu, Fei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Richard Henderson, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Wu, Fei, 2023/03/23
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Richard Henderson, 2023/03/24
- Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Wu, Fei, 2023/03/23
Re: [PATCH v4 1/2] target/riscv: separate priv from mmu_idx, Richard Henderson, 2023/03/23
[PATCH v4 2/2] target/riscv: reduce overhead of MSTATUS_SUM change, Fei Wu, 2023/03/22