Re: [Qemu-arm] [PATCH 04/13] target/arm: Mask PMU register writes based on PMCR_EL0.N

[Aaron Lindsay <alindsay@codeaurora.org>]

On Oct 17 14:41, Peter Maydell wrote:
> On 30 September 2017 at 03:08, Aaron Lindsay <alindsay@codeaurora.org> wrote:
> > This is in preparation for enabling counters other than PMCCNTR
> >
> > Signed-off-by: Aaron Lindsay <alindsay@codeaurora.org>
> > ---
> >  target/arm/helper.c | 24 +++++++++++++++---------
> >  1 file changed, 15 insertions(+), 9 deletions(-)
> >
> > diff --git a/target/arm/helper.c b/target/arm/helper.c
> > index ecf8c55..54070a3 100644
> > --- a/target/arm/helper.c
> > +++ b/target/arm/helper.c
> > @@ -30,11 +30,6 @@ static bool get_phys_addr_lpae(CPUARMState *env, target_ulong address,
> >                                 hwaddr *phys_ptr, MemTxAttrs *txattrs, int *prot,
> >                                 target_ulong *page_size_ptr, uint32_t *fsr,
> >                                 ARMMMUFaultInfo *fi);
> > -
> > -/* Definitions for the PMCCNTR and PMCR registers */
> > -#define PMCRD   0x8
> > -#define PMCRC   0x4
> > -#define PMCRE   0x1
> >  #endif
> >
> >  static int vfp_gdb_get_reg(CPUARMState *env, uint8_t *buf, int reg)
> > @@ -876,6 +871,17 @@ static const ARMCPRegInfo v6_cp_reginfo[] = {
> >      REGINFO_SENTINEL
> >  };
> >
> > +/* Definitions for the PMU registers */
> > +#define PMCRN   0xf800
> 
> We usually name this kind of whole-field mask value something like PMCRN_MASK.
> 
> (We also have a FIELD() macro in hw/registerfields.h for defining
> mask/length/shift constants; though it can be a bit verbose in
> the length of the names it uses, so I don't insist on its use
> if you don't like the results. I'm on the fence myself about it.)

Will do.

> > +#define PMCRN_SHIFT 11
> > +#define PMCRD   0x8
> > +#define PMCRC   0x4
> > +#define PMCRE   0x1
> > +
> > +#define PMU_NUM_COUNTERS(env) ((env->cp15.c9_pmcr & PMCRN) >> PMCRN_SHIFT)
> > +/* Bits allowed to be set/cleared for PMCNTEN* and PMINTEN* */
> > +#define PMU_COUNTER_MASK(env) ((1 << 31) | ((1 << PMU_NUM_COUNTERS(env)) - 1))
> > +
> >  static CPAccessResult pmreg_access(CPUARMState *env, const ARMCPRegInfo *ri,
> >                                     bool isread)
> >  {
> > @@ -1060,14 +1066,14 @@ static void pmccfiltr_write(CPUARMState *env, const ARMCPRegInfo *ri,
> >  static void pmcntenset_write(CPUARMState *env, const ARMCPRegInfo *ri,
> >                              uint64_t value)
> >  {
> > -    value &= (1 << 31);
> > +    value &= (PMU_COUNTER_MASK(env) | (1 << 31));
> 
> PMU_COUNTER_MASK always contains bit 31, so why do we manually OR it in
> again here?

I forgot I'd also included the cycle counter in PMU_COUNTER_MASK... I'll
remove the duplication here and in pmcntenclr_write below.

> >      env->cp15.c9_pmcnten |= value;
> >  }
> >
> >  static void pmcntenclr_write(CPUARMState *env, const ARMCPRegInfo *ri,
> >                               uint64_t value)
> >  {
> > -    value &= (1 << 31);
> > +    value &= (PMU_COUNTER_MASK(env) | (1 << 31));
> >      env->cp15.c9_pmcnten &= ~value;
> >  }
> >
> > @@ -1115,14 +1121,14 @@ static void pmintenset_write(CPUARMState *env, const ARMCPRegInfo *ri,
> >                               uint64_t value)
> >  {
> >      /* We have no event counters so only the C bit can be changed */
> > -    value &= (1 << 31);
> > +    value &= PMU_COUNTER_MASK(env);
> >      env->cp15.c9_pminten |= value;
> >  }
> >
> >  static void pmintenclr_write(CPUARMState *env, const ARMCPRegInfo *ri,
> >                               uint64_t value)
> >  {
> > -    value &= (1 << 31);
> > +    value &= PMU_COUNTER_MASK(env);
> >      env->cp15.c9_pminten &= ~value;
> >  }
> >
> > --
> > Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.\nQualcomm Technologies, Inc. is a member of the\nCode Aurora Forum, a Linux Foundation Collaborative Project.
> 
> Shouldn't these '\n' in your sig be literal line breaks? :-)

Yes :( ...apparently `git config` doesn't interpret them as I expected.

> thanks
> -- PMM

-- 
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.