diff mbox series

[v5,07/12] target/riscv: Support mcycle/minstret write operation

Message ID 20220219002518.1936806-8-atishp@rivosinc.com (mailing list archive)
State New, archived
Headers show
Series Improve PMU support | expand

Commit Message

Atish Kumar Patra Feb. 19, 2022, 12:25 a.m. UTC
From: Atish Patra <atish.patra@wdc.com>

mcycle/minstret are actually WARL registers and can be written with any
given value. With SBI PMU extension, it will be used to store a initial
value provided from supervisor OS. The Qemu also need prohibit the counter
increment if mcountinhibit is set.

Support mcycle/minstret through generic counter infrastructure.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 target/riscv/cpu.h       |  23 +++++--
 target/riscv/csr.c       | 145 +++++++++++++++++++++++++++------------
 target/riscv/machine.c   |  25 ++++++-
 target/riscv/meson.build |   1 +
 target/riscv/pmu.c       |  32 +++++++++
 target/riscv/pmu.h       |  28 ++++++++
 6 files changed, 201 insertions(+), 53 deletions(-)
 create mode 100644 target/riscv/pmu.c
 create mode 100644 target/riscv/pmu.h

Comments

Alistair Francis March 1, 2022, 6:14 a.m. UTC | #1
On Sat, Feb 19, 2022 at 10:32 AM Atish Patra <atishp@rivosinc.com> wrote:
>
> From: Atish Patra <atish.patra@wdc.com>
>
> mcycle/minstret are actually WARL registers and can be written with any
> given value. With SBI PMU extension, it will be used to store a initial
> value provided from supervisor OS. The Qemu also need prohibit the counter
> increment if mcountinhibit is set.
>
> Support mcycle/minstret through generic counter infrastructure.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> Signed-off-by: Atish Patra <atishp@rivosinc.com>
> ---
>  target/riscv/cpu.h       |  23 +++++--
>  target/riscv/csr.c       | 145 +++++++++++++++++++++++++++------------
>  target/riscv/machine.c   |  25 ++++++-
>  target/riscv/meson.build |   1 +
>  target/riscv/pmu.c       |  32 +++++++++
>  target/riscv/pmu.h       |  28 ++++++++
>  6 files changed, 201 insertions(+), 53 deletions(-)
>  create mode 100644 target/riscv/pmu.c
>  create mode 100644 target/riscv/pmu.h
>
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index cce5c3538c89..68522acda4d2 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -109,7 +109,7 @@ typedef struct CPURISCVState CPURISCVState;
>  #endif
>
>  #define RV_VLEN_MAX 1024
> -#define RV_MAX_MHPMEVENTS 29
> +#define RV_MAX_MHPMEVENTS 32
>  #define RV_MAX_MHPMCOUNTERS 32
>
>  FIELD(VTYPE, VLMUL, 0, 3)
> @@ -119,6 +119,18 @@ FIELD(VTYPE, VMA, 7, 1)
>  FIELD(VTYPE, VEDIV, 8, 2)
>  FIELD(VTYPE, RESERVED, 10, sizeof(target_ulong) * 8 - 11)
>
> +typedef struct PMUCTRState {
> +    /* Current value of a counter */
> +    target_ulong mhpmcounter_val;
> +    /* Current value of a counter in RV32*/
> +    target_ulong mhpmcounterh_val;
> +    /* Snapshot values of counter */
> +    target_ulong mhpmcounter_prev;
> +    /* Snapshort value of a counter in RV32 */
> +    target_ulong mhpmcounterh_prev;
> +    bool started;
> +} PMUCTRState;
> +
>  struct CPURISCVState {
>      target_ulong gpr[32];
>      target_ulong gprh[32]; /* 64 top bits of the 128-bit registers */
> @@ -263,13 +275,10 @@ struct CPURISCVState {
>
>      target_ulong mcountinhibit;
>
> -    /* PMU counter configured values */
> -    target_ulong mhpmcounter_val[RV_MAX_MHPMCOUNTERS];
> -
> -    /* for RV32 */
> -    target_ulong mhpmcounterh_val[RV_MAX_MHPMCOUNTERS];
> +    /* PMU counter state */
> +    PMUCTRState pmu_ctrs[RV_MAX_MHPMCOUNTERS];
>
> -    /* PMU event selector configured values */
> +    /* PMU event selector configured values. First three are unused*/
>      target_ulong mhpmevent_val[RV_MAX_MHPMEVENTS];
>
>      target_ulong sscratch;
> diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> index dbb723a3307b..dc4d258205b3 100644
> --- a/target/riscv/csr.c
> +++ b/target/riscv/csr.c
> @@ -20,6 +20,7 @@
>  #include "qemu/osdep.h"
>  #include "qemu/log.h"
>  #include "cpu.h"
> +#include "pmu.h"
>  #include "qemu/main-loop.h"
>  #include "exec/exec-all.h"
>
> @@ -539,39 +540,33 @@ static int write_vcsr(CPURISCVState *env, int csrno, target_ulong val)
>  }
>
>  /* User Timers and Counters */
> -static RISCVException read_instret(CPURISCVState *env, int csrno,
> -                                   target_ulong *val)
> +static target_ulong get_icount_ticks(bool rv32)

Maybe get_ticks() instead?

Also rv32 could be something more descriptive, maybe just shift instead?

Otherwise:

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

Alistair

>  {
> +    int64_t val;
> +    target_ulong result;
> +
>  #if !defined(CONFIG_USER_ONLY)
>      if (icount_enabled()) {
> -        *val = icount_get();
> +        val = icount_get();
>      } else {
> -        *val = cpu_get_host_ticks();
> +        val = cpu_get_host_ticks();
>      }
>  #else
> -    *val = cpu_get_host_ticks();
> +    val = cpu_get_host_ticks();
>  #endif
> -    return RISCV_EXCP_NONE;
> -}
>
> -static RISCVException read_instreth(CPURISCVState *env, int csrno,
> -                                    target_ulong *val)
> -{
> -#if !defined(CONFIG_USER_ONLY)
> -    if (icount_enabled()) {
> -        *val = icount_get() >> 32;
> +    if (rv32) {
> +        result = val >> 32;
>      } else {
> -        *val = cpu_get_host_ticks() >> 32;
> +        result = val;
>      }
> -#else
> -    *val = cpu_get_host_ticks() >> 32;
> -#endif
> -    return RISCV_EXCP_NONE;
> +
> +    return result;
>  }
>
>  static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
>  {
> -    int evt_index = csrno - CSR_MHPMEVENT3;
> +    int evt_index = csrno - CSR_MCOUNTINHIBIT;
>
>      *val = env->mhpmevent_val[evt_index];
>
> @@ -580,7 +575,7 @@ static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
>
>  static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
>  {
> -    int evt_index = csrno - CSR_MHPMEVENT3;
> +    int evt_index = csrno - CSR_MCOUNTINHIBIT;
>
>      env->mhpmevent_val[evt_index] = val;
>
> @@ -589,52 +584,102 @@ static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
>
>  static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
>  {
> -    int ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
> +    int ctr_idx = csrno - CSR_MCYCLE;
> +    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
>
> -    env->mhpmcounter_val[ctr_index] = val;
> +    counter->mhpmcounter_val = val;
> +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> +        counter->mhpmcounter_prev = get_icount_ticks(false);
> +    } else {
> +        /* Other counters can keep incrementing from the given value */
> +        counter->mhpmcounter_prev = val;
> +    }
>
>      return RISCV_EXCP_NONE;
>  }
>
>  static int write_mhpmcounterh(CPURISCVState *env, int csrno, target_ulong val)
>  {
> -    int ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
> +    int ctr_idx = csrno - CSR_MCYCLEH;
> +    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
>
> -    env->mhpmcounterh_val[ctr_index] = val;
> +    counter->mhpmcounterh_val = val;
> +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> +        counter->mhpmcounterh_prev = get_icount_ticks(true);
> +    } else {
> +        counter->mhpmcounterh_prev = val;
> +    }
> +
> +    return RISCV_EXCP_NONE;
> +}
> +
> +static RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val,
> +                                         bool upper_half, uint32_t ctr_idx)
> +{
> +    PMUCTRState counter = env->pmu_ctrs[ctr_idx];
> +    target_ulong ctr_prev = upper_half ? counter.mhpmcounterh_prev :
> +                                         counter.mhpmcounter_prev;
> +    target_ulong ctr_val = upper_half ? counter.mhpmcounterh_val :
> +                                        counter.mhpmcounter_val;
> +
> +    if (get_field(env->mcountinhibit, BIT(ctr_idx))) {
> +        /**
> +         * Counter should not increment if inhibit bit is set. We can't really
> +         * stop the icount counting. Just return the counter value written by
> +         * the supervisor to indicate that counter was not incremented.
> +         */
> +        if (!counter.started) {
> +            *val = ctr_val;
> +            return RISCV_EXCP_NONE;
> +        } else {
> +            /* Mark that the counter has been stopped */
> +            counter.started = false;
> +        }
> +    }
> +
> +
> +    /**
> +     * The kernel computes the perf delta by subtracting the current value from
> +     * the value it initialized previously (ctr_val).
> +     */
> +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> +        *val = get_icount_ticks(upper_half) - ctr_prev + ctr_val;
> +    } else {
> +        *val = ctr_val;
> +    }
>
>      return RISCV_EXCP_NONE;
>  }
>
>  static int read_hpmcounter(CPURISCVState *env, int csrno, target_ulong *val)
>  {
> -    int ctr_index;
> +    uint16_t ctr_index;
>
>      if (env->priv == PRV_M) {
> -        ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
> +        ctr_index = csrno - CSR_MCYCLE;
>      } else {
> -        ctr_index = csrno - CSR_HPMCOUNTER3 + 3;
> +        ctr_index = csrno - CSR_CYCLE;
>      }
> -    *val = env->mhpmcounter_val[ctr_index];
>
> -    return RISCV_EXCP_NONE;
> +    return riscv_pmu_read_ctr(env, val, false, ctr_index);
>  }
>
>  static int read_hpmcounterh(CPURISCVState *env, int csrno, target_ulong *val)
>  {
> -    int ctr_index;
> +    uint16_t ctr_index;
>
>      if (env->priv == PRV_M) {
> -        ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
> +        ctr_index = csrno - CSR_MCYCLEH;
>      } else {
> -        ctr_index = csrno - CSR_HPMCOUNTER3H + 3;
> +        ctr_index = csrno - CSR_CYCLEH;
>      }
>
> -    *val = env->mhpmcounterh_val[ctr_index];
> -
> -    return RISCV_EXCP_NONE;
> +    return riscv_pmu_read_ctr(env, val, true, ctr_index);
>  }
>
> -
>  #if defined(CONFIG_USER_ONLY)
>  static RISCVException read_time(CPURISCVState *env, int csrno,
>                                  target_ulong *val)
> @@ -1468,11 +1513,23 @@ static RISCVException read_mcountinhibit(CPURISCVState *env, int csrno,
>  static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno,
>                                            target_ulong val)
>  {
> +    int cidx;
> +    PMUCTRState *counter;
> +
>      if (env->priv_ver < PRIV_VERSION_1_11_0) {
>          return RISCV_EXCP_ILLEGAL_INST;
>      }
>
>      env->mcountinhibit = val;
> +
> +    /* Check if any other counter is also monitoring cycles/instructions */
> +    for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) {
> +        if (!get_field(env->mcountinhibit, BIT(cidx))) {
> +            counter = &env->pmu_ctrs[cidx];
> +            counter->started = true;
> +        }
> +    }
> +
>      return RISCV_EXCP_NONE;
>  }
>
> @@ -3347,10 +3404,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>      [CSR_VLENB]    = { "vlenb",    vs,    read_vlenb,
>                                            .min_priv_ver = PRIV_VERSION_1_12_0 },
>      /* User Timers and Counters */
> -    [CSR_CYCLE]    = { "cycle",    ctr,    read_instret  },
> -    [CSR_INSTRET]  = { "instret",  ctr,    read_instret  },
> -    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_instreth },
> -    [CSR_INSTRETH] = { "instreth", ctr32,  read_instreth },
> +    [CSR_CYCLE]    = { "cycle",    ctr,    read_hpmcounter  },
> +    [CSR_INSTRET]  = { "instret",  ctr,    read_hpmcounter  },
> +    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_hpmcounterh },
> +    [CSR_INSTRETH] = { "instreth", ctr32,  read_hpmcounterh },
>
>      /*
>       * In privileged mode, the monitor will have to emulate TIME CSRs only if
> @@ -3361,10 +3418,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
>
>  #if !defined(CONFIG_USER_ONLY)
>      /* Machine Timers and Counters */
> -    [CSR_MCYCLE]    = { "mcycle",    any,   read_instret  },
> -    [CSR_MINSTRET]  = { "minstret",  any,   read_instret  },
> -    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_instreth },
> -    [CSR_MINSTRETH] = { "minstreth", any32, read_instreth },
> +    [CSR_MCYCLE]    = { "mcycle",    any,   read_hpmcounter, write_mhpmcounter},
> +    [CSR_MINSTRET]  = { "minstret",  any,   read_hpmcounter, write_mhpmcounter},
> +    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_hpmcounterh, write_mhpmcounterh},
> +    [CSR_MINSTRETH] = { "minstreth", any32, read_hpmcounterh, write_mhpmcounterh},
>
>      /* Machine Information Registers */
>      [CSR_MVENDORID] = { "mvendorid", any,   read_zero    },
> diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> index 042d655ce3ef..1f2186935666 100644
> --- a/target/riscv/machine.c
> +++ b/target/riscv/machine.c
> @@ -248,7 +248,28 @@ static const VMStateDescription vmstate_envcfg = {
>          VMSTATE_UINT64(env.menvcfg, RISCVCPU),
>          VMSTATE_UINTTL(env.senvcfg, RISCVCPU),
>          VMSTATE_UINT64(env.henvcfg, RISCVCPU),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
> +static bool pmu_needed(void *opaque)
> +{
> +    RISCVCPU *cpu = opaque;
>
> +    return cpu->cfg.pmu_num;
> +}
> +
> +static const VMStateDescription vmstate_pmu_ctr_state = {
> +    .name = "cpu/pmu",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .needed = pmu_needed,
> +    .fields = (VMStateField[]) {
> +        VMSTATE_UINTTL(mhpmcounter_val, PMUCTRState),
> +        VMSTATE_UINTTL(mhpmcounterh_val, PMUCTRState),
> +        VMSTATE_UINTTL(mhpmcounter_prev, PMUCTRState),
> +        VMSTATE_UINTTL(mhpmcounterh_prev, PMUCTRState),
> +        VMSTATE_BOOL(started, PMUCTRState),
>          VMSTATE_END_OF_LIST()
>      }
>  };
> @@ -300,8 +321,8 @@ const VMStateDescription vmstate_riscv_cpu = {
>          VMSTATE_UINTTL(env.scounteren, RISCVCPU),
>          VMSTATE_UINTTL(env.mcounteren, RISCVCPU),
>          VMSTATE_UINTTL(env.mcountinhibit, RISCVCPU),
> -        VMSTATE_UINTTL_ARRAY(env.mhpmcounter_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
> -        VMSTATE_UINTTL_ARRAY(env.mhpmcounterh_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
> +        VMSTATE_STRUCT_ARRAY(env.pmu_ctrs, RISCVCPU, RV_MAX_MHPMCOUNTERS, 0,
> +                             vmstate_pmu_ctr_state, PMUCTRState),
>          VMSTATE_UINTTL_ARRAY(env.mhpmevent_val, RISCVCPU, RV_MAX_MHPMEVENTS),
>          VMSTATE_UINTTL(env.sscratch, RISCVCPU),
>          VMSTATE_UINTTL(env.mscratch, RISCVCPU),
> diff --git a/target/riscv/meson.build b/target/riscv/meson.build
> index 91f0ac32ff3d..b41967b8c54a 100644
> --- a/target/riscv/meson.build
> +++ b/target/riscv/meson.build
> @@ -27,6 +27,7 @@ riscv_softmmu_ss = ss.source_set()
>  riscv_softmmu_ss.add(files(
>    'arch_dump.c',
>    'pmp.c',
> +  'pmu.c',
>    'monitor.c',
>    'machine.c'
>  ))
> diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> new file mode 100644
> index 000000000000..000fe8da45ef
> --- /dev/null
> +++ b/target/riscv/pmu.c
> @@ -0,0 +1,32 @@
> +/*
> + * RISC-V PMU file.
> + *
> + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "cpu.h"
> +#include "pmu.h"
> +
> +bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
> +                                        uint32_t target_ctr)
> +{
> +    return (target_ctr == 0) ? true : false;
> +}
> +
> +bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env, uint32_t target_ctr)
> +{
> +    return (target_ctr == 2) ? true : false;
> +}
> diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
> new file mode 100644
> index 000000000000..58a5bc3a4089
> --- /dev/null
> +++ b/target/riscv/pmu.h
> @@ -0,0 +1,28 @@
> +/*
> + * RISC-V PMU header file.
> + *
> + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/log.h"
> +#include "cpu.h"
> +#include "qemu/main-loop.h"
> +#include "exec/exec-all.h"
> +
> +bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
> +                                        uint32_t target_ctr);
> +bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env,
> +                                  uint32_t target_ctr);
> --
> 2.30.2
>
>
Atish Kumar Patra March 3, 2022, 8:04 p.m. UTC | #2
On Mon, Feb 28, 2022 at 10:14 PM Alistair Francis <alistair23@gmail.com> wrote:
>
> On Sat, Feb 19, 2022 at 10:32 AM Atish Patra <atishp@rivosinc.com> wrote:
> >
> > From: Atish Patra <atish.patra@wdc.com>
> >
> > mcycle/minstret are actually WARL registers and can be written with any
> > given value. With SBI PMU extension, it will be used to store a initial
> > value provided from supervisor OS. The Qemu also need prohibit the counter
> > increment if mcountinhibit is set.
> >
> > Support mcycle/minstret through generic counter infrastructure.
> >
> > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > Signed-off-by: Atish Patra <atishp@rivosinc.com>
> > ---
> >  target/riscv/cpu.h       |  23 +++++--
> >  target/riscv/csr.c       | 145 +++++++++++++++++++++++++++------------
> >  target/riscv/machine.c   |  25 ++++++-
> >  target/riscv/meson.build |   1 +
> >  target/riscv/pmu.c       |  32 +++++++++
> >  target/riscv/pmu.h       |  28 ++++++++
> >  6 files changed, 201 insertions(+), 53 deletions(-)
> >  create mode 100644 target/riscv/pmu.c
> >  create mode 100644 target/riscv/pmu.h
> >
> > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> > index cce5c3538c89..68522acda4d2 100644
> > --- a/target/riscv/cpu.h
> > +++ b/target/riscv/cpu.h
> > @@ -109,7 +109,7 @@ typedef struct CPURISCVState CPURISCVState;
> >  #endif
> >
> >  #define RV_VLEN_MAX 1024
> > -#define RV_MAX_MHPMEVENTS 29
> > +#define RV_MAX_MHPMEVENTS 32
> >  #define RV_MAX_MHPMCOUNTERS 32
> >
> >  FIELD(VTYPE, VLMUL, 0, 3)
> > @@ -119,6 +119,18 @@ FIELD(VTYPE, VMA, 7, 1)
> >  FIELD(VTYPE, VEDIV, 8, 2)
> >  FIELD(VTYPE, RESERVED, 10, sizeof(target_ulong) * 8 - 11)
> >
> > +typedef struct PMUCTRState {
> > +    /* Current value of a counter */
> > +    target_ulong mhpmcounter_val;
> > +    /* Current value of a counter in RV32*/
> > +    target_ulong mhpmcounterh_val;
> > +    /* Snapshot values of counter */
> > +    target_ulong mhpmcounter_prev;
> > +    /* Snapshort value of a counter in RV32 */
> > +    target_ulong mhpmcounterh_prev;
> > +    bool started;
> > +} PMUCTRState;
> > +
> >  struct CPURISCVState {
> >      target_ulong gpr[32];
> >      target_ulong gprh[32]; /* 64 top bits of the 128-bit registers */
> > @@ -263,13 +275,10 @@ struct CPURISCVState {
> >
> >      target_ulong mcountinhibit;
> >
> > -    /* PMU counter configured values */
> > -    target_ulong mhpmcounter_val[RV_MAX_MHPMCOUNTERS];
> > -
> > -    /* for RV32 */
> > -    target_ulong mhpmcounterh_val[RV_MAX_MHPMCOUNTERS];
> > +    /* PMU counter state */
> > +    PMUCTRState pmu_ctrs[RV_MAX_MHPMCOUNTERS];
> >
> > -    /* PMU event selector configured values */
> > +    /* PMU event selector configured values. First three are unused*/
> >      target_ulong mhpmevent_val[RV_MAX_MHPMEVENTS];
> >
> >      target_ulong sscratch;
> > diff --git a/target/riscv/csr.c b/target/riscv/csr.c
> > index dbb723a3307b..dc4d258205b3 100644
> > --- a/target/riscv/csr.c
> > +++ b/target/riscv/csr.c
> > @@ -20,6 +20,7 @@
> >  #include "qemu/osdep.h"
> >  #include "qemu/log.h"
> >  #include "cpu.h"
> > +#include "pmu.h"
> >  #include "qemu/main-loop.h"
> >  #include "exec/exec-all.h"
> >
> > @@ -539,39 +540,33 @@ static int write_vcsr(CPURISCVState *env, int csrno, target_ulong val)
> >  }
> >
> >  /* User Timers and Counters */
> > -static RISCVException read_instret(CPURISCVState *env, int csrno,
> > -                                   target_ulong *val)
> > +static target_ulong get_icount_ticks(bool rv32)
>
> Maybe get_ticks() instead?
>

Sure. Will rename it.


> Also rv32 could be something more descriptive, maybe just shift instead?
>

Sure. Will change it.

> Otherwise:
>
> Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
>
> Alistair
>
> >  {
> > +    int64_t val;
> > +    target_ulong result;
> > +
> >  #if !defined(CONFIG_USER_ONLY)
> >      if (icount_enabled()) {
> > -        *val = icount_get();
> > +        val = icount_get();
> >      } else {
> > -        *val = cpu_get_host_ticks();
> > +        val = cpu_get_host_ticks();
> >      }
> >  #else
> > -    *val = cpu_get_host_ticks();
> > +    val = cpu_get_host_ticks();
> >  #endif
> > -    return RISCV_EXCP_NONE;
> > -}
> >
> > -static RISCVException read_instreth(CPURISCVState *env, int csrno,
> > -                                    target_ulong *val)
> > -{
> > -#if !defined(CONFIG_USER_ONLY)
> > -    if (icount_enabled()) {
> > -        *val = icount_get() >> 32;
> > +    if (rv32) {
> > +        result = val >> 32;
> >      } else {
> > -        *val = cpu_get_host_ticks() >> 32;
> > +        result = val;
> >      }
> > -#else
> > -    *val = cpu_get_host_ticks() >> 32;
> > -#endif
> > -    return RISCV_EXCP_NONE;
> > +
> > +    return result;
> >  }
> >
> >  static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
> >  {
> > -    int evt_index = csrno - CSR_MHPMEVENT3;
> > +    int evt_index = csrno - CSR_MCOUNTINHIBIT;
> >
> >      *val = env->mhpmevent_val[evt_index];
> >
> > @@ -580,7 +575,7 @@ static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
> >
> >  static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
> >  {
> > -    int evt_index = csrno - CSR_MHPMEVENT3;
> > +    int evt_index = csrno - CSR_MCOUNTINHIBIT;
> >
> >      env->mhpmevent_val[evt_index] = val;
> >
> > @@ -589,52 +584,102 @@ static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
> >
> >  static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
> >  {
> > -    int ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
> > +    int ctr_idx = csrno - CSR_MCYCLE;
> > +    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
> >
> > -    env->mhpmcounter_val[ctr_index] = val;
> > +    counter->mhpmcounter_val = val;
> > +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> > +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > +        counter->mhpmcounter_prev = get_icount_ticks(false);
> > +    } else {
> > +        /* Other counters can keep incrementing from the given value */
> > +        counter->mhpmcounter_prev = val;
> > +    }
> >
> >      return RISCV_EXCP_NONE;
> >  }
> >
> >  static int write_mhpmcounterh(CPURISCVState *env, int csrno, target_ulong val)
> >  {
> > -    int ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
> > +    int ctr_idx = csrno - CSR_MCYCLEH;
> > +    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
> >
> > -    env->mhpmcounterh_val[ctr_index] = val;
> > +    counter->mhpmcounterh_val = val;
> > +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> > +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > +        counter->mhpmcounterh_prev = get_icount_ticks(true);
> > +    } else {
> > +        counter->mhpmcounterh_prev = val;
> > +    }
> > +
> > +    return RISCV_EXCP_NONE;
> > +}
> > +
> > +static RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val,
> > +                                         bool upper_half, uint32_t ctr_idx)
> > +{
> > +    PMUCTRState counter = env->pmu_ctrs[ctr_idx];
> > +    target_ulong ctr_prev = upper_half ? counter.mhpmcounterh_prev :
> > +                                         counter.mhpmcounter_prev;
> > +    target_ulong ctr_val = upper_half ? counter.mhpmcounterh_val :
> > +                                        counter.mhpmcounter_val;
> > +
> > +    if (get_field(env->mcountinhibit, BIT(ctr_idx))) {
> > +        /**
> > +         * Counter should not increment if inhibit bit is set. We can't really
> > +         * stop the icount counting. Just return the counter value written by
> > +         * the supervisor to indicate that counter was not incremented.
> > +         */
> > +        if (!counter.started) {
> > +            *val = ctr_val;
> > +            return RISCV_EXCP_NONE;
> > +        } else {
> > +            /* Mark that the counter has been stopped */
> > +            counter.started = false;
> > +        }
> > +    }
> > +
> > +
> > +    /**
> > +     * The kernel computes the perf delta by subtracting the current value from
> > +     * the value it initialized previously (ctr_val).
> > +     */
> > +    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
> > +        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
> > +        *val = get_icount_ticks(upper_half) - ctr_prev + ctr_val;
> > +    } else {
> > +        *val = ctr_val;
> > +    }
> >
> >      return RISCV_EXCP_NONE;
> >  }
> >
> >  static int read_hpmcounter(CPURISCVState *env, int csrno, target_ulong *val)
> >  {
> > -    int ctr_index;
> > +    uint16_t ctr_index;
> >
> >      if (env->priv == PRV_M) {
> > -        ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
> > +        ctr_index = csrno - CSR_MCYCLE;
> >      } else {
> > -        ctr_index = csrno - CSR_HPMCOUNTER3 + 3;
> > +        ctr_index = csrno - CSR_CYCLE;
> >      }
> > -    *val = env->mhpmcounter_val[ctr_index];
> >
> > -    return RISCV_EXCP_NONE;
> > +    return riscv_pmu_read_ctr(env, val, false, ctr_index);
> >  }
> >
> >  static int read_hpmcounterh(CPURISCVState *env, int csrno, target_ulong *val)
> >  {
> > -    int ctr_index;
> > +    uint16_t ctr_index;
> >
> >      if (env->priv == PRV_M) {
> > -        ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
> > +        ctr_index = csrno - CSR_MCYCLEH;
> >      } else {
> > -        ctr_index = csrno - CSR_HPMCOUNTER3H + 3;
> > +        ctr_index = csrno - CSR_CYCLEH;
> >      }
> >
> > -    *val = env->mhpmcounterh_val[ctr_index];
> > -
> > -    return RISCV_EXCP_NONE;
> > +    return riscv_pmu_read_ctr(env, val, true, ctr_index);
> >  }
> >
> > -
> >  #if defined(CONFIG_USER_ONLY)
> >  static RISCVException read_time(CPURISCVState *env, int csrno,
> >                                  target_ulong *val)
> > @@ -1468,11 +1513,23 @@ static RISCVException read_mcountinhibit(CPURISCVState *env, int csrno,
> >  static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno,
> >                                            target_ulong val)
> >  {
> > +    int cidx;
> > +    PMUCTRState *counter;
> > +
> >      if (env->priv_ver < PRIV_VERSION_1_11_0) {
> >          return RISCV_EXCP_ILLEGAL_INST;
> >      }
> >
> >      env->mcountinhibit = val;
> > +
> > +    /* Check if any other counter is also monitoring cycles/instructions */
> > +    for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) {
> > +        if (!get_field(env->mcountinhibit, BIT(cidx))) {
> > +            counter = &env->pmu_ctrs[cidx];
> > +            counter->started = true;
> > +        }
> > +    }
> > +
> >      return RISCV_EXCP_NONE;
> >  }
> >
> > @@ -3347,10 +3404,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
> >      [CSR_VLENB]    = { "vlenb",    vs,    read_vlenb,
> >                                            .min_priv_ver = PRIV_VERSION_1_12_0 },
> >      /* User Timers and Counters */
> > -    [CSR_CYCLE]    = { "cycle",    ctr,    read_instret  },
> > -    [CSR_INSTRET]  = { "instret",  ctr,    read_instret  },
> > -    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_instreth },
> > -    [CSR_INSTRETH] = { "instreth", ctr32,  read_instreth },
> > +    [CSR_CYCLE]    = { "cycle",    ctr,    read_hpmcounter  },
> > +    [CSR_INSTRET]  = { "instret",  ctr,    read_hpmcounter  },
> > +    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_hpmcounterh },
> > +    [CSR_INSTRETH] = { "instreth", ctr32,  read_hpmcounterh },
> >
> >      /*
> >       * In privileged mode, the monitor will have to emulate TIME CSRs only if
> > @@ -3361,10 +3418,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
> >
> >  #if !defined(CONFIG_USER_ONLY)
> >      /* Machine Timers and Counters */
> > -    [CSR_MCYCLE]    = { "mcycle",    any,   read_instret  },
> > -    [CSR_MINSTRET]  = { "minstret",  any,   read_instret  },
> > -    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_instreth },
> > -    [CSR_MINSTRETH] = { "minstreth", any32, read_instreth },
> > +    [CSR_MCYCLE]    = { "mcycle",    any,   read_hpmcounter, write_mhpmcounter},
> > +    [CSR_MINSTRET]  = { "minstret",  any,   read_hpmcounter, write_mhpmcounter},
> > +    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_hpmcounterh, write_mhpmcounterh},
> > +    [CSR_MINSTRETH] = { "minstreth", any32, read_hpmcounterh, write_mhpmcounterh},
> >
> >      /* Machine Information Registers */
> >      [CSR_MVENDORID] = { "mvendorid", any,   read_zero    },
> > diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> > index 042d655ce3ef..1f2186935666 100644
> > --- a/target/riscv/machine.c
> > +++ b/target/riscv/machine.c
> > @@ -248,7 +248,28 @@ static const VMStateDescription vmstate_envcfg = {
> >          VMSTATE_UINT64(env.menvcfg, RISCVCPU),
> >          VMSTATE_UINTTL(env.senvcfg, RISCVCPU),
> >          VMSTATE_UINT64(env.henvcfg, RISCVCPU),
> > +        VMSTATE_END_OF_LIST()
> > +    }
> > +};
> > +
> > +static bool pmu_needed(void *opaque)
> > +{
> > +    RISCVCPU *cpu = opaque;
> >
> > +    return cpu->cfg.pmu_num;
> > +}
> > +
> > +static const VMStateDescription vmstate_pmu_ctr_state = {
> > +    .name = "cpu/pmu",
> > +    .version_id = 1,
> > +    .minimum_version_id = 1,
> > +    .needed = pmu_needed,
> > +    .fields = (VMStateField[]) {
> > +        VMSTATE_UINTTL(mhpmcounter_val, PMUCTRState),
> > +        VMSTATE_UINTTL(mhpmcounterh_val, PMUCTRState),
> > +        VMSTATE_UINTTL(mhpmcounter_prev, PMUCTRState),
> > +        VMSTATE_UINTTL(mhpmcounterh_prev, PMUCTRState),
> > +        VMSTATE_BOOL(started, PMUCTRState),
> >          VMSTATE_END_OF_LIST()
> >      }
> >  };
> > @@ -300,8 +321,8 @@ const VMStateDescription vmstate_riscv_cpu = {
> >          VMSTATE_UINTTL(env.scounteren, RISCVCPU),
> >          VMSTATE_UINTTL(env.mcounteren, RISCVCPU),
> >          VMSTATE_UINTTL(env.mcountinhibit, RISCVCPU),
> > -        VMSTATE_UINTTL_ARRAY(env.mhpmcounter_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
> > -        VMSTATE_UINTTL_ARRAY(env.mhpmcounterh_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
> > +        VMSTATE_STRUCT_ARRAY(env.pmu_ctrs, RISCVCPU, RV_MAX_MHPMCOUNTERS, 0,
> > +                             vmstate_pmu_ctr_state, PMUCTRState),
> >          VMSTATE_UINTTL_ARRAY(env.mhpmevent_val, RISCVCPU, RV_MAX_MHPMEVENTS),
> >          VMSTATE_UINTTL(env.sscratch, RISCVCPU),
> >          VMSTATE_UINTTL(env.mscratch, RISCVCPU),
> > diff --git a/target/riscv/meson.build b/target/riscv/meson.build
> > index 91f0ac32ff3d..b41967b8c54a 100644
> > --- a/target/riscv/meson.build
> > +++ b/target/riscv/meson.build
> > @@ -27,6 +27,7 @@ riscv_softmmu_ss = ss.source_set()
> >  riscv_softmmu_ss.add(files(
> >    'arch_dump.c',
> >    'pmp.c',
> > +  'pmu.c',
> >    'monitor.c',
> >    'machine.c'
> >  ))
> > diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> > new file mode 100644
> > index 000000000000..000fe8da45ef
> > --- /dev/null
> > +++ b/target/riscv/pmu.c
> > @@ -0,0 +1,32 @@
> > +/*
> > + * RISC-V PMU file.
> > + *
> > + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms and conditions of the GNU General Public License,
> > + * version 2 or later, as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope it will be useful, but WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> > + * more details.
> > + *
> > + * You should have received a copy of the GNU General Public License along with
> > + * this program.  If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "cpu.h"
> > +#include "pmu.h"
> > +
> > +bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
> > +                                        uint32_t target_ctr)
> > +{
> > +    return (target_ctr == 0) ? true : false;
> > +}
> > +
> > +bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env, uint32_t target_ctr)
> > +{
> > +    return (target_ctr == 2) ? true : false;
> > +}
> > diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
> > new file mode 100644
> > index 000000000000..58a5bc3a4089
> > --- /dev/null
> > +++ b/target/riscv/pmu.h
> > @@ -0,0 +1,28 @@
> > +/*
> > + * RISC-V PMU header file.
> > + *
> > + * Copyright (c) 2021 Western Digital Corporation or its affiliates.
> > + *
> > + * This program is free software; you can redistribute it and/or modify it
> > + * under the terms and conditions of the GNU General Public License,
> > + * version 2 or later, as published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope it will be useful, but WITHOUT
> > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> > + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> > + * more details.
> > + *
> > + * You should have received a copy of the GNU General Public License along with
> > + * this program.  If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "qemu/log.h"
> > +#include "cpu.h"
> > +#include "qemu/main-loop.h"
> > +#include "exec/exec-all.h"
> > +
> > +bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
> > +                                        uint32_t target_ctr);
> > +bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env,
> > +                                  uint32_t target_ctr);
> > --
> > 2.30.2
> >
> >
diff mbox series

Patch

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index cce5c3538c89..68522acda4d2 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -109,7 +109,7 @@  typedef struct CPURISCVState CPURISCVState;
 #endif
 
 #define RV_VLEN_MAX 1024
-#define RV_MAX_MHPMEVENTS 29
+#define RV_MAX_MHPMEVENTS 32
 #define RV_MAX_MHPMCOUNTERS 32
 
 FIELD(VTYPE, VLMUL, 0, 3)
@@ -119,6 +119,18 @@  FIELD(VTYPE, VMA, 7, 1)
 FIELD(VTYPE, VEDIV, 8, 2)
 FIELD(VTYPE, RESERVED, 10, sizeof(target_ulong) * 8 - 11)
 
+typedef struct PMUCTRState {
+    /* Current value of a counter */
+    target_ulong mhpmcounter_val;
+    /* Current value of a counter in RV32*/
+    target_ulong mhpmcounterh_val;
+    /* Snapshot values of counter */
+    target_ulong mhpmcounter_prev;
+    /* Snapshort value of a counter in RV32 */
+    target_ulong mhpmcounterh_prev;
+    bool started;
+} PMUCTRState;
+
 struct CPURISCVState {
     target_ulong gpr[32];
     target_ulong gprh[32]; /* 64 top bits of the 128-bit registers */
@@ -263,13 +275,10 @@  struct CPURISCVState {
 
     target_ulong mcountinhibit;
 
-    /* PMU counter configured values */
-    target_ulong mhpmcounter_val[RV_MAX_MHPMCOUNTERS];
-
-    /* for RV32 */
-    target_ulong mhpmcounterh_val[RV_MAX_MHPMCOUNTERS];
+    /* PMU counter state */
+    PMUCTRState pmu_ctrs[RV_MAX_MHPMCOUNTERS];
 
-    /* PMU event selector configured values */
+    /* PMU event selector configured values. First three are unused*/
     target_ulong mhpmevent_val[RV_MAX_MHPMEVENTS];
 
     target_ulong sscratch;
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index dbb723a3307b..dc4d258205b3 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -20,6 +20,7 @@ 
 #include "qemu/osdep.h"
 #include "qemu/log.h"
 #include "cpu.h"
+#include "pmu.h"
 #include "qemu/main-loop.h"
 #include "exec/exec-all.h"
 
@@ -539,39 +540,33 @@  static int write_vcsr(CPURISCVState *env, int csrno, target_ulong val)
 }
 
 /* User Timers and Counters */
-static RISCVException read_instret(CPURISCVState *env, int csrno,
-                                   target_ulong *val)
+static target_ulong get_icount_ticks(bool rv32)
 {
+    int64_t val;
+    target_ulong result;
+
 #if !defined(CONFIG_USER_ONLY)
     if (icount_enabled()) {
-        *val = icount_get();
+        val = icount_get();
     } else {
-        *val = cpu_get_host_ticks();
+        val = cpu_get_host_ticks();
     }
 #else
-    *val = cpu_get_host_ticks();
+    val = cpu_get_host_ticks();
 #endif
-    return RISCV_EXCP_NONE;
-}
 
-static RISCVException read_instreth(CPURISCVState *env, int csrno,
-                                    target_ulong *val)
-{
-#if !defined(CONFIG_USER_ONLY)
-    if (icount_enabled()) {
-        *val = icount_get() >> 32;
+    if (rv32) {
+        result = val >> 32;
     } else {
-        *val = cpu_get_host_ticks() >> 32;
+        result = val;
     }
-#else
-    *val = cpu_get_host_ticks() >> 32;
-#endif
-    return RISCV_EXCP_NONE;
+
+    return result;
 }
 
 static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    int evt_index = csrno - CSR_MHPMEVENT3;
+    int evt_index = csrno - CSR_MCOUNTINHIBIT;
 
     *val = env->mhpmevent_val[evt_index];
 
@@ -580,7 +575,7 @@  static int read_mhpmevent(CPURISCVState *env, int csrno, target_ulong *val)
 
 static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
 {
-    int evt_index = csrno - CSR_MHPMEVENT3;
+    int evt_index = csrno - CSR_MCOUNTINHIBIT;
 
     env->mhpmevent_val[evt_index] = val;
 
@@ -589,52 +584,102 @@  static int write_mhpmevent(CPURISCVState *env, int csrno, target_ulong val)
 
 static int write_mhpmcounter(CPURISCVState *env, int csrno, target_ulong val)
 {
-    int ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
+    int ctr_idx = csrno - CSR_MCYCLE;
+    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
 
-    env->mhpmcounter_val[ctr_index] = val;
+    counter->mhpmcounter_val = val;
+    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
+        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
+        counter->mhpmcounter_prev = get_icount_ticks(false);
+    } else {
+        /* Other counters can keep incrementing from the given value */
+        counter->mhpmcounter_prev = val;
+    }
 
     return RISCV_EXCP_NONE;
 }
 
 static int write_mhpmcounterh(CPURISCVState *env, int csrno, target_ulong val)
 {
-    int ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
+    int ctr_idx = csrno - CSR_MCYCLEH;
+    PMUCTRState *counter = &env->pmu_ctrs[ctr_idx];
 
-    env->mhpmcounterh_val[ctr_index] = val;
+    counter->mhpmcounterh_val = val;
+    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
+        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
+        counter->mhpmcounterh_prev = get_icount_ticks(true);
+    } else {
+        counter->mhpmcounterh_prev = val;
+    }
+
+    return RISCV_EXCP_NONE;
+}
+
+static RISCVException riscv_pmu_read_ctr(CPURISCVState *env, target_ulong *val,
+                                         bool upper_half, uint32_t ctr_idx)
+{
+    PMUCTRState counter = env->pmu_ctrs[ctr_idx];
+    target_ulong ctr_prev = upper_half ? counter.mhpmcounterh_prev :
+                                         counter.mhpmcounter_prev;
+    target_ulong ctr_val = upper_half ? counter.mhpmcounterh_val :
+                                        counter.mhpmcounter_val;
+
+    if (get_field(env->mcountinhibit, BIT(ctr_idx))) {
+        /**
+         * Counter should not increment if inhibit bit is set. We can't really
+         * stop the icount counting. Just return the counter value written by
+         * the supervisor to indicate that counter was not incremented.
+         */
+        if (!counter.started) {
+            *val = ctr_val;
+            return RISCV_EXCP_NONE;
+        } else {
+            /* Mark that the counter has been stopped */
+            counter.started = false;
+        }
+    }
+
+
+    /**
+     * The kernel computes the perf delta by subtracting the current value from
+     * the value it initialized previously (ctr_val).
+     */
+    if (riscv_pmu_ctr_monitor_cycles(env, ctr_idx) ||
+        riscv_pmu_ctr_monitor_instructions(env, ctr_idx)) {
+        *val = get_icount_ticks(upper_half) - ctr_prev + ctr_val;
+    } else {
+        *val = ctr_val;
+    }
 
     return RISCV_EXCP_NONE;
 }
 
 static int read_hpmcounter(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    int ctr_index;
+    uint16_t ctr_index;
 
     if (env->priv == PRV_M) {
-        ctr_index = csrno - CSR_MHPMCOUNTER3 + 3;
+        ctr_index = csrno - CSR_MCYCLE;
     } else {
-        ctr_index = csrno - CSR_HPMCOUNTER3 + 3;
+        ctr_index = csrno - CSR_CYCLE;
     }
-    *val = env->mhpmcounter_val[ctr_index];
 
-    return RISCV_EXCP_NONE;
+    return riscv_pmu_read_ctr(env, val, false, ctr_index);
 }
 
 static int read_hpmcounterh(CPURISCVState *env, int csrno, target_ulong *val)
 {
-    int ctr_index;
+    uint16_t ctr_index;
 
     if (env->priv == PRV_M) {
-        ctr_index = csrno - CSR_MHPMCOUNTER3H + 3;
+        ctr_index = csrno - CSR_MCYCLEH;
     } else {
-        ctr_index = csrno - CSR_HPMCOUNTER3H + 3;
+        ctr_index = csrno - CSR_CYCLEH;
     }
 
-    *val = env->mhpmcounterh_val[ctr_index];
-
-    return RISCV_EXCP_NONE;
+    return riscv_pmu_read_ctr(env, val, true, ctr_index);
 }
 
-
 #if defined(CONFIG_USER_ONLY)
 static RISCVException read_time(CPURISCVState *env, int csrno,
                                 target_ulong *val)
@@ -1468,11 +1513,23 @@  static RISCVException read_mcountinhibit(CPURISCVState *env, int csrno,
 static RISCVException write_mcountinhibit(CPURISCVState *env, int csrno,
                                           target_ulong val)
 {
+    int cidx;
+    PMUCTRState *counter;
+
     if (env->priv_ver < PRIV_VERSION_1_11_0) {
         return RISCV_EXCP_ILLEGAL_INST;
     }
 
     env->mcountinhibit = val;
+
+    /* Check if any other counter is also monitoring cycles/instructions */
+    for (cidx = 0; cidx < RV_MAX_MHPMCOUNTERS; cidx++) {
+        if (!get_field(env->mcountinhibit, BIT(cidx))) {
+            counter = &env->pmu_ctrs[cidx];
+            counter->started = true;
+        }
+    }
+
     return RISCV_EXCP_NONE;
 }
 
@@ -3347,10 +3404,10 @@  riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
     [CSR_VLENB]    = { "vlenb",    vs,    read_vlenb,
                                           .min_priv_ver = PRIV_VERSION_1_12_0 },
     /* User Timers and Counters */
-    [CSR_CYCLE]    = { "cycle",    ctr,    read_instret  },
-    [CSR_INSTRET]  = { "instret",  ctr,    read_instret  },
-    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_instreth },
-    [CSR_INSTRETH] = { "instreth", ctr32,  read_instreth },
+    [CSR_CYCLE]    = { "cycle",    ctr,    read_hpmcounter  },
+    [CSR_INSTRET]  = { "instret",  ctr,    read_hpmcounter  },
+    [CSR_CYCLEH]   = { "cycleh",   ctr32,  read_hpmcounterh },
+    [CSR_INSTRETH] = { "instreth", ctr32,  read_hpmcounterh },
 
     /*
      * In privileged mode, the monitor will have to emulate TIME CSRs only if
@@ -3361,10 +3418,10 @@  riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
 
 #if !defined(CONFIG_USER_ONLY)
     /* Machine Timers and Counters */
-    [CSR_MCYCLE]    = { "mcycle",    any,   read_instret  },
-    [CSR_MINSTRET]  = { "minstret",  any,   read_instret  },
-    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_instreth },
-    [CSR_MINSTRETH] = { "minstreth", any32, read_instreth },
+    [CSR_MCYCLE]    = { "mcycle",    any,   read_hpmcounter, write_mhpmcounter},
+    [CSR_MINSTRET]  = { "minstret",  any,   read_hpmcounter, write_mhpmcounter},
+    [CSR_MCYCLEH]   = { "mcycleh",   any32, read_hpmcounterh, write_mhpmcounterh},
+    [CSR_MINSTRETH] = { "minstreth", any32, read_hpmcounterh, write_mhpmcounterh},
 
     /* Machine Information Registers */
     [CSR_MVENDORID] = { "mvendorid", any,   read_zero    },
diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index 042d655ce3ef..1f2186935666 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -248,7 +248,28 @@  static const VMStateDescription vmstate_envcfg = {
         VMSTATE_UINT64(env.menvcfg, RISCVCPU),
         VMSTATE_UINTTL(env.senvcfg, RISCVCPU),
         VMSTATE_UINT64(env.henvcfg, RISCVCPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static bool pmu_needed(void *opaque)
+{
+    RISCVCPU *cpu = opaque;
 
+    return cpu->cfg.pmu_num;
+}
+
+static const VMStateDescription vmstate_pmu_ctr_state = {
+    .name = "cpu/pmu",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = pmu_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINTTL(mhpmcounter_val, PMUCTRState),
+        VMSTATE_UINTTL(mhpmcounterh_val, PMUCTRState),
+        VMSTATE_UINTTL(mhpmcounter_prev, PMUCTRState),
+        VMSTATE_UINTTL(mhpmcounterh_prev, PMUCTRState),
+        VMSTATE_BOOL(started, PMUCTRState),
         VMSTATE_END_OF_LIST()
     }
 };
@@ -300,8 +321,8 @@  const VMStateDescription vmstate_riscv_cpu = {
         VMSTATE_UINTTL(env.scounteren, RISCVCPU),
         VMSTATE_UINTTL(env.mcounteren, RISCVCPU),
         VMSTATE_UINTTL(env.mcountinhibit, RISCVCPU),
-        VMSTATE_UINTTL_ARRAY(env.mhpmcounter_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
-        VMSTATE_UINTTL_ARRAY(env.mhpmcounterh_val, RISCVCPU, RV_MAX_MHPMCOUNTERS),
+        VMSTATE_STRUCT_ARRAY(env.pmu_ctrs, RISCVCPU, RV_MAX_MHPMCOUNTERS, 0,
+                             vmstate_pmu_ctr_state, PMUCTRState),
         VMSTATE_UINTTL_ARRAY(env.mhpmevent_val, RISCVCPU, RV_MAX_MHPMEVENTS),
         VMSTATE_UINTTL(env.sscratch, RISCVCPU),
         VMSTATE_UINTTL(env.mscratch, RISCVCPU),
diff --git a/target/riscv/meson.build b/target/riscv/meson.build
index 91f0ac32ff3d..b41967b8c54a 100644
--- a/target/riscv/meson.build
+++ b/target/riscv/meson.build
@@ -27,6 +27,7 @@  riscv_softmmu_ss = ss.source_set()
 riscv_softmmu_ss.add(files(
   'arch_dump.c',
   'pmp.c',
+  'pmu.c',
   'monitor.c',
   'machine.c'
 ))
diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
new file mode 100644
index 000000000000..000fe8da45ef
--- /dev/null
+++ b/target/riscv/pmu.c
@@ -0,0 +1,32 @@ 
+/*
+ * RISC-V PMU file.
+ *
+ * Copyright (c) 2021 Western Digital Corporation or its affiliates.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "pmu.h"
+
+bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
+                                        uint32_t target_ctr)
+{
+    return (target_ctr == 0) ? true : false;
+}
+
+bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env, uint32_t target_ctr)
+{
+    return (target_ctr == 2) ? true : false;
+}
diff --git a/target/riscv/pmu.h b/target/riscv/pmu.h
new file mode 100644
index 000000000000..58a5bc3a4089
--- /dev/null
+++ b/target/riscv/pmu.h
@@ -0,0 +1,28 @@ 
+/*
+ * RISC-V PMU header file.
+ *
+ * Copyright (c) 2021 Western Digital Corporation or its affiliates.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/log.h"
+#include "cpu.h"
+#include "qemu/main-loop.h"
+#include "exec/exec-all.h"
+
+bool riscv_pmu_ctr_monitor_instructions(CPURISCVState *env,
+                                        uint32_t target_ctr);
+bool riscv_pmu_ctr_monitor_cycles(CPURISCVState *env,
+                                  uint32_t target_ctr);