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Re: [PATCH v10 09/12] target/riscv: Simplify counter predicate function
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From: |
Atish Kumar Patra |
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Subject: |
Re: [PATCH v10 09/12] target/riscv: Simplify counter predicate function |
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Date: |
Tue, 5 Jul 2022 01:00:50 -0700 |
On Mon, Jul 4, 2022 at 8:19 AM Weiwei Li <liweiwei@iscas.ac.cn> wrote:
>
>
> 在 2022/6/21 上午7:15, Atish Patra 写道:
>
> All the hpmcounters and the fixed counters (CY, IR, TM) can be represented
> as a unified counter. Thus, the predicate function doesn't need handle each
> case separately.
>
> Simplify the predicate function so that we just handle things differently
> between RV32/RV64 and S/HS mode.
>
> Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
> Acked-by: Alistair Francis <alistair.francis@wdc.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
> target/riscv/csr.c | 112 +++++----------------------------------------
> 1 file changed, 11 insertions(+), 101 deletions(-)
>
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index 2664ce265784..9367e2af9b90 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -74,6 +74,7 @@ static RISCVException ctr(CPURISCVState *env, int csrno)
> CPUState *cs = env_cpu(env);
> RISCVCPU *cpu = RISCV_CPU(cs);
> int ctr_index;
> + target_ulong ctr_mask;
> int base_csrno = CSR_CYCLE;
> bool rv32 = riscv_cpu_mxl(env) == MXL_RV32 ? true : false;
>
> @@ -82,122 +83,31 @@ static RISCVException ctr(CPURISCVState *env, int csrno)
> base_csrno += 0x80;
> }
> ctr_index = csrno - base_csrno;
> + ctr_mask = BIT(ctr_index);
>
> if ((csrno >= CSR_CYCLE && csrno <= CSR_INSTRET) ||
> (csrno >= CSR_CYCLEH && csrno <= CSR_INSTRETH)) {
> goto skip_ext_pmu_check;
> }
>
> - if ((!cpu->cfg.pmu_num || !(cpu->pmu_avail_ctrs & BIT(ctr_index)))) {
> + if ((!cpu->cfg.pmu_num || !(cpu->pmu_avail_ctrs & ctr_mask))) {
> /* No counter is enabled in PMU or the counter is out of range */
> return RISCV_EXCP_ILLEGAL_INST;
> }
>
> skip_ext_pmu_check:
>
> - if (env->priv == PRV_S) {
> - switch (csrno) {
> - case CSR_CYCLE:
> - if (!get_field(env->mcounteren, COUNTEREN_CY)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_TIME:
> - if (!get_field(env->mcounteren, COUNTEREN_TM)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_INSTRET:
> - if (!get_field(env->mcounteren, COUNTEREN_IR)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_HPMCOUNTER3...CSR_HPMCOUNTER31:
> - if (!get_field(env->mcounteren, 1 << ctr_index)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - }
> - if (rv32) {
> - switch (csrno) {
> - case CSR_CYCLEH:
> - if (!get_field(env->mcounteren, COUNTEREN_CY)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_TIMEH:
> - if (!get_field(env->mcounteren, COUNTEREN_TM)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_INSTRETH:
> - if (!get_field(env->mcounteren, COUNTEREN_IR)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - case CSR_HPMCOUNTER3H...CSR_HPMCOUNTER31H:
> - if (!get_field(env->mcounteren, 1 << ctr_index)) {
> - return RISCV_EXCP_ILLEGAL_INST;
> - }
> - break;
> - }
> - }
> + if (((env->priv == PRV_S) && (!get_field(env->mcounteren, ctr_mask))) ||
> + ((env->priv == PRV_U) && (!get_field(env->scounteren, ctr_mask)))) {
> + return RISCV_EXCP_ILLEGAL_INST;
> }
>
> Sorry. I didn't realize this simplification and sent a similar patch to fix
> the problems in Xcounteren
>
> related check I found when I tried to learn the patchset for state enable
> extension two days ago.
>
> I think there are several difference between our understanding, following is
> my modifications:
>
> + if (csrno <= CSR_HPMCOUNTER31 && csrno >= CSR_CYCLE) {
> + field = 1 << (csrno - CSR_CYCLE);
> + } else if (riscv_cpu_mxl(env) == MXL_RV32 && csrno <= CSR_HPMCOUNTER31H
> &&
> + csrno >= CSR_CYCLEH) {
> + field = 1 << (csrno - CSR_CYCLEH);
> + }
> +
> + if (env->priv < PRV_M && !get_field(env->mcounteren, field)) {
> + return RISCV_EXCP_ILLEGAL_INST;
> + }
> +
> + if (riscv_cpu_virt_enabled(env) && !get_field(env->hcounteren, field)) {
> + return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> + }
> +
> + if (riscv_has_ext(env, RVS) && env->priv == PRV_U &&
> + !get_field(env->scounteren, field)) {
> + if (riscv_cpu_virt_enabled(env)) {
> + return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> + } else {
> + return RISCV_EXCP_ILLEGAL_INST;
> }
> }
>
>
> 1) For any less-privileged mode under M, illegal exception is raised if
> matching
> bit in mcounteren is zero.
>
As per the priv spec, in the section 3.1.11
"When one of these bits is set, access to the corresponding register
is permitted in the next implemented privilege mode (S-mode if
implemented, otherwise U-mode)."
mcounteren controls the access for U-mode only if the next implemented
mode is U (riscv_has_ext(env, RVS) must be false).
I did not add the additional check as the ctr is defined only for
!CONFIG_USER_ONLY.
> 2) For VS/VU mode('H' extension is supported implicitly), virtual instruction
> exception is raised if matching bit in hcounteren is zero.
>
> 3) scounteren csr only works in U/VU mode when 'S' extension is supported:
Yes. But we don't need additional check for 'S' extension as it will
be done by the predicate function "smode"
> For U mode, illegal exception is raised if matching bit in scounteren is
> zero.
> For VU mode, virtual instruction exception exception is raised if matching
> bit
> in scounteren is zero.
>
> Regards,
> Weiwei Li
>
>
> if (riscv_cpu_virt_enabled(env)) {
> - switch (csrno) {
> - case CSR_CYCLE:
> - if (!get_field(env->hcounteren, COUNTEREN_CY) &&
> - get_field(env->mcounteren, COUNTEREN_CY)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_TIME:
> - if (!get_field(env->hcounteren, COUNTEREN_TM) &&
> - get_field(env->mcounteren, COUNTEREN_TM)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_INSTRET:
> - if (!get_field(env->hcounteren, COUNTEREN_IR) &&
> - get_field(env->mcounteren, COUNTEREN_IR)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_HPMCOUNTER3...CSR_HPMCOUNTER31:
> - if (!get_field(env->hcounteren, 1 << ctr_index) &&
> - get_field(env->mcounteren, 1 << ctr_index)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - }
> - if (rv32) {
> - switch (csrno) {
> - case CSR_CYCLEH:
> - if (!get_field(env->hcounteren, COUNTEREN_CY) &&
> - get_field(env->mcounteren, COUNTEREN_CY)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_TIMEH:
> - if (!get_field(env->hcounteren, COUNTEREN_TM) &&
> - get_field(env->mcounteren, COUNTEREN_TM)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_INSTRETH:
> - if (!get_field(env->hcounteren, COUNTEREN_IR) &&
> - get_field(env->mcounteren, COUNTEREN_IR)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - case CSR_HPMCOUNTER3H...CSR_HPMCOUNTER31H:
> - if (!get_field(env->hcounteren, 1 << ctr_index) &&
> - get_field(env->mcounteren, 1 << ctr_index)) {
> - return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> - }
> - break;
> - }
> + if (!get_field(env->mcounteren, ctr_mask)) {
> + /* The bit must be set in mcountern for HS mode access */
> + return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> + } else if (!get_field(env->hcounteren, ctr_mask)) {
> + return RISCV_EXCP_VIRT_INSTRUCTION_FAULT;
> }
> }
> #endif