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

[Rob Bradford]

On Thu, 2023-10-12 at 17:05 +0800, LIU Zhiwei wrote:
>  
> 
>  
>  
> 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.
>  

Good point, thanks Zhiwei. I think rather than masking those bits it is
better to add a check and error out if those bits are set.

Cheers,

Rob

> Zhiwei
>  
>  
> >  
> >  }
> >  
>