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Re: What's the correct way to implement rfi and related instruction.


From: Yonggang Luo
Subject: Re: What's the correct way to implement rfi and related instruction.
Date: Fri, 8 Jan 2021 12:21:17 +0800



On Fri, Jan 8, 2021 at 5:54 AM Cédric Le Goater <clg@kaod.org> wrote:
>
> On 1/7/21 8:14 PM, 罗勇刚(Yonggang Luo) wrote:
> > This is the first patch,:
> > It's store MSR bits differntly for different rfi instructions:
> > [Qemu-devel] [PATCH] target-ppc: fix RFI by clearing some bits of MSR
> > https://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02999.html <https://lists.gnu.org/archive/html/qemu-devel/2010-05/msg02999.html>
> > Comes from  target-ppc: fix RFI by clearing some bits of MSR
> > SHA-1: c3d420ead1aee9fcfd12be11cbdf6b1620134773
> >  target-ppc/op_helper.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> > ```
> > diff --git a/target-ppc/op_helper.c b/target-ppc/op_helper.c
> > index 8f2ee986bb..3c3aa60bc3 100644
> > --- a/target-ppc/op_helper.c
> > +++ b/target-ppc/op_helper.c
> > @@ -1646,20 +1646,20 @@ static inline void do_rfi(target_ulong nip, target_ulong msr,
> >  void helper_rfi (void)
> >  {
> >      do_rfi(env->spr[SPR_SRR0], env->spr[SPR_SRR1],
> > -           ~((target_ulong)0x0), 1);
> > +           ~((target_ulong)0x783F0000), 1);
> >  }
> >  
> >  #if defined(TARGET_PPC64)
> >  void helper_rfid (void)
> >  {
> >      do_rfi(env->spr[SPR_SRR0], env->spr[SPR_SRR1],
> > -           ~((target_ulong)0x0), 0);
> > +           ~((target_ulong)0x783F0000), 0);
> >  }
> >  
> >  void helper_hrfid (void)
> >  {
> >      do_rfi(env->spr[SPR_HSRR0], env->spr[SPR_HSRR1],
> > -           ~((target_ulong)0x0), 0);
> > +           ~((target_ulong)0x783F0000), 0);
> >  }
> >  #endif
> >  #endif
> > ```
> >
> > This is the second patch,:
> > it's remove the parameter  `target_ulong msrm, int keep_msrh`
> > Comes from ppc: Fix rfi/rfid/hrfi/... emulation
> > SHA-1: a2e71b28e832346409efc795ecd1f0a2bcb705a3
> > ```
> >  target-ppc/excp_helper.c | 51 +++++++++++++++++++-----------------------------
> >  1 file changed, 20 insertions(+), 31 deletions(-)
> >
> > diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
> > index 30e960e30b..aa0b63f4b0 100644
> > --- a/target-ppc/excp_helper.c
> > +++ b/target-ppc/excp_helper.c
> > @@ -922,25 +922,20 @@ void helper_store_msr(CPUPPCState *env, target_ulong val)
> >      }
> >  }
> >  
> > -static inline void do_rfi(CPUPPCState *env, target_ulong nip, target_ulong msr,
> > -                          target_ulong msrm, int keep_msrh)
> > +static inline void do_rfi(CPUPPCState *env, target_ulong nip, target_ulong msr)
> >  {
> >      CPUState *cs = CPU(ppc_env_get_cpu(env));
> >  
> > +    /* MSR:POW cannot be set by any form of rfi */
> > +    msr &= ~(1ULL << MSR_POW);
> > +
> >  #if defined(TARGET_PPC64)
> > -    if (msr_is_64bit(env, msr)) {
> > -        nip = (uint64_t)nip;
> > -        msr &= (uint64_t)msrm;
> > -    } else {
> > +    /* Switching to 32-bit ? Crop the nip */
> > +    if (!msr_is_64bit(env, msr)) {
> >          nip = (uint32_t)nip;
> > -        msr = (uint32_t)(msr & msrm);
> > -        if (keep_msrh) {
> > -            msr |= env->msr & ~((uint64_t)0xFFFFFFFF);
> > -        }
> >      }
> >  #else
> >      nip = (uint32_t)nip;
> > -    msr &= (uint32_t)msrm;
> >  #endif
> >      /* XXX: beware: this is false if VLE is supported */
> >      env->nip = nip & ~((target_ulong)0x00000003);
> > @@ -959,26 +954,24 @@ static inline void do_rfi(CPUPPCState *env, target_ulong nip, target_ulong msr,
> >  
> >  void helper_rfi(CPUPPCState *env)
> >  {
> > -    if (env->excp_model == POWERPC_EXCP_BOOKE) {
> > -        do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1],
> > -               ~((target_ulong)0), 0);
> > -    } else {
> > -        do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1],
> > -               ~((target_ulong)0x783F0000), 1);
> > -    }
> > +    do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1] & 0xfffffffful);
> >  }
> >  
> > +#define MSR_BOOK3S_MASK
> >  #if defined(TARGET_PPC64)
> >  void helper_rfid(CPUPPCState *env)
> >  {
> > -    do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1],
> > -           ~((target_ulong)0x783F0000), 0);
> > +    /* The architeture defines a number of rules for which bits
> > +     * can change but in practice, we handle this in hreg_store_msr()
> > +     * which will be called by do_rfi(), so there is no need to filter
> > +     * here
> > +     */
> > +    do_rfi(env, env->spr[SPR_SRR0], env->spr[SPR_SRR1]);
> >  }
> >  
> >  void helper_hrfid(CPUPPCState *env)
> >  {
> > -    do_rfi(env, env->spr[SPR_HSRR0], env->spr[SPR_HSRR1],
> > -           ~((target_ulong)0x783F0000), 0);
> > +    do_rfi(env, env->spr[SPR_HSRR0], env->spr[SPR_HSRR1]);
> >  }
> >  #endif
> >  
> > @@ -986,28 +979,24 @@ void helper_hrfid(CPUPPCState *env)
> >  /* Embedded PowerPC specific helpers */
> >  void helper_40x_rfci(CPUPPCState *env)
> >  {
> > -    do_rfi(env, env->spr[SPR_40x_SRR2], env->spr[SPR_40x_SRR3],
> > -           ~((target_ulong)0xFFFF0000), 0);
> > +    do_rfi(env, env->spr[SPR_40x_SRR2], env->spr[SPR_40x_SRR3]);
> >  }
> >  
> >  void helper_rfci(CPUPPCState *env)
> >  {
> > -    do_rfi(env, env->spr[SPR_BOOKE_CSRR0], env->spr[SPR_BOOKE_CSRR1],
> > -           ~((target_ulong)0), 0);
> > +    do_rfi(env, env->spr[SPR_BOOKE_CSRR0], env->spr[SPR_BOOKE_CSRR1]);
> >  }
> >  
> >  void helper_rfdi(CPUPPCState *env)
> >  {
> >      /* FIXME: choose CSRR1 or DSRR1 based on cpu type */
> > -    do_rfi(env, env->spr[SPR_BOOKE_DSRR0], env->spr[SPR_BOOKE_DSRR1],
> > -           ~((target_ulong)0), 0);
> > +    do_rfi(env, env->spr[SPR_BOOKE_DSRR0], env->spr[SPR_BOOKE_DSRR1]);
> >  }
> >  
> >  void helper_rfmci(CPUPPCState *env)
> >  {
> >      /* FIXME: choose CSRR1 or MCSRR1 based on cpu type */
> > -    do_rfi(env, env->spr[SPR_BOOKE_MCSRR0], env->spr[SPR_BOOKE_MCSRR1],
> > -           ~((target_ulong)0), 0);
> > +    do_rfi(env, env->spr[SPR_BOOKE_MCSRR0], env->spr[SPR_BOOKE_MCSRR1]);
> >  }
> >  #endif
> >  
> > @@ -1045,7 +1034,7 @@ void helper_td(CPUPPCState *env, target_ulong arg1, target_ulong arg2,
> >  
> >  void helper_rfsvc(CPUPPCState *env)
> >  {
> > -    do_rfi(env, env->lr, env->ctr, 0x0000FFFF, 0);
> > +    do_rfi(env, env->lr, env->ctr & 0x0000FFFF);
> >  }
> >  
> >  /* Embedded.Processor Control */
> > ```
> >
> > And of cause, the second patch fixes some problem, but also cause new problem,
> > how to implement these instruction properly?
>
> What are the new problems  ?
Before this patch, VxWorks can working, but after this, VxWorks can not boot anymore.

>
> C.
>
> >
> >
> >
> > --
> >          此致
> > 礼
> > 罗勇刚
> > Yours
> >     sincerely,
> > Yonggang Luo
>


--
         此致

罗勇刚
Yours
    sincerely,
Yonggang Luo

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