Re: [Qemu-devel] [QEMU-PPC] [PATCH 1/4] target/ppc/spapr: Add SPAPR_CAP_LARGE_DECREMENTER

[Suraj Jitindar Singh]

On Tue, 2019-02-26 at 14:39 +1100, David Gibson wrote:
> On Tue, Feb 26, 2019 at 02:05:28PM +1100, Suraj Jitindar Singh wrote:
> > Add spapr_cap SPAPR_CAP_LARGE_DECREMENTER to be used to control the
> > availability and size of the large decrementer made available to
> > the
> > guest.
> > 
> > Signed-off-by: Suraj Jitindar Singh <address@hidden>
> > ---
> >  hw/ppc/spapr.c         |  2 ++
> >  hw/ppc/spapr_caps.c    | 45
> > +++++++++++++++++++++++++++++++++++++++++++++
> >  include/hw/ppc/spapr.h |  5 ++++-
> >  3 files changed, 51 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index b6a571b6f1..acf62a2b9f 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -2077,6 +2077,7 @@ static const VMStateDescription vmstate_spapr
> > = {
> >          &vmstate_spapr_irq_map,
> >          &vmstate_spapr_cap_nested_kvm_hv,
> >          &vmstate_spapr_dtb,
> > +        &vmstate_spapr_cap_large_decr,
> >          NULL
> >      }
> >  };
> > @@ -4288,6 +4289,7 @@ static void
> > spapr_machine_class_init(ObjectClass *oc, void *data)
> >      smc->default_caps.caps[SPAPR_CAP_IBS] = SPAPR_CAP_BROKEN;
> >      smc->default_caps.caps[SPAPR_CAP_HPT_MAXPAGESIZE] = 16; /*
> > 64kiB */
> >      smc->default_caps.caps[SPAPR_CAP_NESTED_KVM_HV] =
> > SPAPR_CAP_OFF;
> > +    smc->default_caps.caps[SPAPR_CAP_LARGE_DECREMENTER] = 0;
> 
> This looks basically fine, but the name kind of suggests it's a
> boolean, whereas it's actually a number of bits.  I wonder if just
> calling it "decrementer bits" would be clearer, with it defaulting to
> 32.

Yes, except there's a difference between a decrementer with 32 bits and
a large decrementer with 32 bits...

SPAPR_CAP_LARGE_DECR_NR_BITS?

> 
> >      spapr_caps_add_properties(smc, &error_abort);
> >      smc->irq = &spapr_irq_xics;
> >      smc->dr_phb_enabled = true;
> > diff --git a/hw/ppc/spapr_caps.c b/hw/ppc/spapr_caps.c
> > index 64f98ae68d..1545a02729 100644
> > --- a/hw/ppc/spapr_caps.c
> > +++ b/hw/ppc/spapr_caps.c
> > @@ -182,6 +182,34 @@ static void spapr_cap_set_pagesize(Object
> > *obj, Visitor *v, const char *name,
> >      spapr->eff.caps[cap->index] = val;
> >  }
> >  
> > +static void spapr_cap_get_uint8(Object *obj, Visitor *v, const
> > char *name,
> > +                                void *opaque, Error **errp)
> > +{
> > +    sPAPRCapabilityInfo *cap = opaque;
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> > +    uint8_t val = spapr_get_cap(spapr, cap->index);
> > +
> > +    visit_type_uint8(v, name, &val, errp);
> > +}
> > +
> > +static void spapr_cap_set_uint8(Object *obj, Visitor *v, const
> > char *name,
> > +                                void *opaque, Error **errp)
> > +{
> > +    sPAPRCapabilityInfo *cap = opaque;
> > +    sPAPRMachineState *spapr = SPAPR_MACHINE(obj);
> > +    Error *local_err = NULL;
> > +    uint8_t val;
> > +
> > +    visit_type_uint8(v, name, &val, &local_err);
> > +    if (local_err) {
> > +        error_propagate(errp, local_err);
> > +        return;
> > +    }
> > +
> > +    spapr->cmd_line_caps[cap->index] = true;
> > +    spapr->eff.caps[cap->index] = val;
> > +}
> > +
> >  static void cap_htm_apply(sPAPRMachineState *spapr, uint8_t val,
> > Error **errp)
> >  {
> >      if (!val) {
> > @@ -390,6 +418,13 @@ static void
> > cap_nested_kvm_hv_apply(sPAPRMachineState *spapr,
> >      }
> >  }
> >  
> > +static void cap_large_decr_apply(sPAPRMachineState *spapr,
> > +                                 uint8_t val, Error **errp)
> > +{
> > +    if (val)
> > +        error_setg(errp, "No large decrementer support, try cap-
> > large-decr=0");
> > +}
> > +
> >  sPAPRCapabilityInfo capability_table[SPAPR_CAP_NUM] = {
> >      [SPAPR_CAP_HTM] = {
> >          .name = "htm",
> > @@ -468,6 +503,15 @@ sPAPRCapabilityInfo
> > capability_table[SPAPR_CAP_NUM] = {
> >          .type = "bool",
> >          .apply = cap_nested_kvm_hv_apply,
> >      },
> > +    [SPAPR_CAP_LARGE_DECREMENTER] = {
> > +        .name = "large-decr",
> > +        .description = "Size of Large Decrementer for the Guest
> > (bits) 0=disabled",
> > +        .index = SPAPR_CAP_LARGE_DECREMENTER,
> > +        .get = spapr_cap_get_uint8,
> > +        .set = spapr_cap_set_uint8,
> > +        .type = "int",
> > +        .apply = cap_large_decr_apply,
> > +    },
> >  };
> >  
> >  static sPAPRCapabilities default_caps_with_cpu(sPAPRMachineState
> > *spapr,
> > @@ -596,6 +640,7 @@ SPAPR_CAP_MIG_STATE(cfpc, SPAPR_CAP_CFPC);
> >  SPAPR_CAP_MIG_STATE(sbbc, SPAPR_CAP_SBBC);
> >  SPAPR_CAP_MIG_STATE(ibs, SPAPR_CAP_IBS);
> >  SPAPR_CAP_MIG_STATE(nested_kvm_hv, SPAPR_CAP_NESTED_KVM_HV);
> > +SPAPR_CAP_MIG_STATE(large_decr, SPAPR_CAP_LARGE_DECREMENTER);
> >  
> >  void spapr_caps_init(sPAPRMachineState *spapr)
> >  {
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index 59073a7579..8efc5e0779 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -74,8 +74,10 @@ typedef enum {
> >  #define SPAPR_CAP_HPT_MAXPAGESIZE       0x06
> >  /* Nested KVM-HV */
> >  #define SPAPR_CAP_NESTED_KVM_HV         0x07
> > +/* Large Decrementer */
> > +#define SPAPR_CAP_LARGE_DECREMENTER     0x08
> >  /* Num Caps */
> > -#define SPAPR_CAP_NUM                   (SPAPR_CAP_NESTED_KVM_HV +
> > 1)
> > +#define
> > SPAPR_CAP_NUM                   (SPAPR_CAP_LARGE_DECREMENTER + 1)
> >  
> >  /*
> >   * Capability Values
> > @@ -828,6 +830,7 @@ extern const VMStateDescription
> > vmstate_spapr_cap_cfpc;
> >  extern const VMStateDescription vmstate_spapr_cap_sbbc;
> >  extern const VMStateDescription vmstate_spapr_cap_ibs;
> >  extern const VMStateDescription vmstate_spapr_cap_nested_kvm_hv;
> > +extern const VMStateDescription vmstate_spapr_cap_large_decr;
> >  
> >  static inline uint8_t spapr_get_cap(sPAPRMachineState *spapr, int
> > cap)
> >  {
> 
>