Re: [PATCH v2 5/6] target/riscv: Add "pmu-mask" property to replace "pmu-num"

[LIU Zhiwei <baxiantai@gmail.com>]

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On 2023/10/11 22:45, Rob Bradford wrote:
> Using a mask instead of the number of PMU devices supports the accurate
> emulation of platforms that have a discontinuous set of PMU counters.
>
> Generate a warning if the old property changed from the default but
> still go ahead and use it to generate the mask if the user has changed
> it from the default
>
> Signed-off-by: Rob Bradford<rbradford@rivosinc.com>
> ---
>   target/riscv/cpu.c     |  5 +++--
>   target/riscv/cpu_cfg.h |  3 ++-
>   target/riscv/machine.c |  2 +-
>   target/riscv/pmu.c     | 14 ++++++++++----
>   4 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index c9d8fc12fe..4d2987e568 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -1487,7 +1487,7 @@ static void riscv_cpu_realize_tcg(DeviceState *dev, Error **errp)
>           riscv_timer_init(cpu);
>       }
>   
> -    if (cpu->cfg.pmu_num) {
> +    if (cpu->cfg.pmu_mask) {
>           riscv_pmu_init(cpu, &local_err);
>           if (local_err != NULL) {
>               error_propagate(errp, local_err);
> @@ -1812,7 +1812,8 @@ static void riscv_cpu_add_misa_properties(Object *cpu_obj)
>   
>   static Property riscv_cpu_extensions[] = {
>       /* Defaults for standard extensions */
> -    DEFINE_PROP_UINT8("pmu-num", RISCVCPU, cfg.pmu_num, 16),
> +    DEFINE_PROP_UINT8("pmu-num", RISCVCPU, cfg.pmu_num, 16), /* Deprecated */
> +    DEFINE_PROP_UINT32("pmu-mask", RISCVCPU, cfg.pmu_mask, MAKE_32BIT_MASK(3, 16)),
>       DEFINE_PROP_BOOL("sscofpmf", RISCVCPU, cfg.ext_sscofpmf, false),
>       DEFINE_PROP_BOOL("Zifencei", RISCVCPU, cfg.ext_ifencei, true),
>       DEFINE_PROP_BOOL("Zicsr", RISCVCPU, cfg.ext_icsr, true),
> diff --git a/target/riscv/cpu_cfg.h b/target/riscv/cpu_cfg.h
> index 0e6a0f245c..d273487040 100644
> --- a/target/riscv/cpu_cfg.h
> +++ b/target/riscv/cpu_cfg.h
> @@ -123,7 +123,8 @@ struct RISCVCPUConfig {
>       bool ext_xtheadsync;
>       bool ext_XVentanaCondOps;
>   
> -    uint8_t pmu_num;
> +    uint8_t pmu_num; /* Deprecated */
> +    uint32_t pmu_mask;
>       char *priv_spec;
>       char *user_spec;
>       char *bext_spec;
> diff --git a/target/riscv/machine.c b/target/riscv/machine.c
> index c7c862cdd3..9f6e3f7a6d 100644
> --- a/target/riscv/machine.c
> +++ b/target/riscv/machine.c
> @@ -313,7 +313,7 @@ static bool pmu_needed(void *opaque)
>   {
>       RISCVCPU *cpu = opaque;
>   
> -    return cpu->cfg.pmu_num;
> +    return (cpu->cfg.pmu_mask > 0);
>   }
>   
>   static const VMStateDescription vmstate_pmu_ctr_state = {
> diff --git a/target/riscv/pmu.c b/target/riscv/pmu.c
> index 360c76f63e..f2d35b4d3b 100644
> --- a/target/riscv/pmu.c
> +++ b/target/riscv/pmu.c
> @@ -18,6 +18,7 @@
>   
>   #include "qemu/osdep.h"
>   #include "qemu/log.h"
> +#include "qemu/error-report.h"
>   #include "cpu.h"
>   #include "pmu.h"
>   #include "sysemu/cpu-timers.h"
> @@ -182,7 +183,7 @@ int riscv_pmu_incr_ctr(RISCVCPU *cpu, enum riscv_pmu_event_idx event_idx)
>       CPURISCVState *env = &cpu->env;
>       gpointer value;
>   
> -    if (!cpu->cfg.pmu_num) {
> +    if (!cpu->cfg.pmu_mask) {
>           return 0;
>       }
>       value = g_hash_table_lookup(cpu->pmu_event_ctr_map,
> @@ -432,7 +433,7 @@ void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
>   {
>       uint8_t pmu_num = cpu->cfg.pmu_num;
>   
> -    if (pmu_num > (RV_MAX_MHPMCOUNTERS - 3)) {
> +    if (ctpop32(cpu->cfg.pmu_mask) > (RV_MAX_MHPMCOUNTERS - 3)) {
>           error_setg(errp, "Number of counters exceeds maximum available");
>           return;
>       }
> @@ -443,6 +444,11 @@ void riscv_pmu_init(RISCVCPU *cpu, Error **errp)
>           return;
>       }
>   
> -    /* Create a bitmask of available programmable counters */
> -    cpu->pmu_avail_ctrs = MAKE_32BIT_MASK(3, pmu_num);
> +    /* Check if user set it by comparing against default */
> +    if (pmu_num != 16) {
> +        warn_report("\"pmu-num\" property is deprecated; use \"pmu-mask\"");
> +        cpu->cfg.pmu_mask = MAKE_32BIT_MASK(3, pmu_num);
> +    }
> +
> +    cpu->pmu_avail_ctrs = cpu->cfg.pmu_mask;

How to process the pmu_mask[0:2] no-zero bits? They should not included 
into pmu_avail_ctrs.

Zhiwei

>   }

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