Re: [PATCH v6 11/18] target/ppc: Only calculate RMLS derived RMA limit on demand

[Greg Kurz <groug@kaod.org>]

On Tue, 25 Feb 2020 10:37:17 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> When the LPCR is written, we update the env->rmls field with the RMA limit
> it implies.  Simplify things by just calculating the value directly from
> the LPCR value when we need it.
> 
> It's possible this is a little slower, but it's unlikely to be significant,
> since this is only for real mode accesses in a translation configuration
> that's not used very often, and the whole thing is behind the qemu TLB
> anyway.  Therefore, keeping the number of state variables down and not
> having to worry about making sure it's always in sync seems the better
> option.
> 

This patch also refactors the code of ppc_hash64_update_vrma(), which
is definitely an improvement, but seems a bit unrelated to the title...
I'd personally make it a separate patch but you decide of course :)

Also, a cosmetic remark. See below.

> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> Reviewed-by: Cédric Le Goater <clg@kaod.org>
> ---
>  target/ppc/cpu.h        |  1 -
>  target/ppc/mmu-hash64.c | 84 ++++++++++++++++++++---------------------
>  2 files changed, 40 insertions(+), 45 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 8077fdb068..f9871b1233 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1046,7 +1046,6 @@ struct CPUPPCState {
>      uint64_t insns_flags2;
>  #if defined(TARGET_PPC64)
>      ppc_slb_t vrma_slb;
> -    target_ulong rmls;
>  #endif
>  
>      int error_code;
> diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> index dd0df6fd01..ac21c14f68 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -791,6 +791,35 @@ static target_ulong rmls_limit(PowerPCCPU *cpu)
>      }
>  }
>  
> +static int build_vrma_slbe(PowerPCCPU *cpu, ppc_slb_t *slb)
> +{
> +    CPUPPCState *env = &cpu->env;
> +    target_ulong lpcr = env->spr[SPR_LPCR];
> +    uint32_t vrmasd = (lpcr & LPCR_VRMASD) >> LPCR_VRMASD_SHIFT;
> +    target_ulong vsid = SLB_VSID_VRMA | ((vrmasd << 4) & SLB_VSID_LLP_MASK);
> +    int i;
> +
> +    for (i = 0; i < PPC_PAGE_SIZES_MAX_SZ; i++) {
> +        const PPCHash64SegmentPageSizes *sps = &cpu->hash64_opts->sps[i];
> +
> +        if (!sps->page_shift) {
> +            break;
> +        }
> +
> +        if ((vsid & SLB_VSID_LLP_MASK) == sps->slb_enc) {
> +            slb->esid = SLB_ESID_V;
> +            slb->vsid = vsid;
> +            slb->sps = sps;
> +            return 0;
> +        }
> +    }
> +
> +    error_report("Bad page size encoding in LPCR[VRMASD]; LPCR=0x"
> +                 TARGET_FMT_lx"\n", lpcr);
> +
> +    return -1;
> +}
> +
>  int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, vaddr eaddr,
>                                  int rwx, int mmu_idx)
>  {
> @@ -844,8 +873,10 @@ int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, vaddr eaddr,
>  
>              goto skip_slb_search;
>          } else {
> +            target_ulong limit = rmls_limit(cpu);
> +
>              /* Emulated old-style RMO mode, bounds check against RMLS */
> -            if (raddr >= env->rmls) {
> +            if (raddr >= limit) {
>                  if (rwx == 2) {
>                      ppc_hash64_set_isi(cs, SRR1_PROTFAULT);
>                  } else {
> @@ -1007,8 +1038,9 @@ hwaddr ppc_hash64_get_phys_page_debug(PowerPCCPU *cpu, target_ulong addr)
>                  return -1;
>              }
>          } else {
> +            target_ulong limit = rmls_limit(cpu);

Maybe add an empty line like you did above for consistency and better
readability ?

Anyway, feel free to add:

Reviewed-by: Greg Kurz <groug@kaod.org>

>              /* Emulated old-style RMO mode, bounds check against RMLS */
> -            if (raddr >= env->rmls) {
> +            if (raddr >= limit) {
>                  return -1;
>              }
>              return raddr | env->spr[SPR_RMOR];
> @@ -1043,53 +1075,18 @@ void ppc_hash64_tlb_flush_hpte(PowerPCCPU *cpu, target_ulong ptex,
>  static void ppc_hash64_update_vrma(PowerPCCPU *cpu)
>  {
>      CPUPPCState *env = &cpu->env;
> -    const PPCHash64SegmentPageSizes *sps = NULL;
> -    target_ulong esid, vsid, lpcr;
>      ppc_slb_t *slb = &env->vrma_slb;
> -    uint32_t vrmasd;
> -    int i;
> -
> -    /* First clear it */
> -    slb->esid = slb->vsid = 0;
> -    slb->sps = NULL;
>  
>      /* Is VRMA enabled ? */
> -    if (!ppc_hash64_use_vrma(env)) {
> -        return;
> -    }
> -
> -    /*
> -     * Make one up. Mostly ignore the ESID which will not be needed
> -     * for translation
> -     */
> -    lpcr = env->spr[SPR_LPCR];
> -    vsid = SLB_VSID_VRMA;
> -    vrmasd = (lpcr & LPCR_VRMASD) >> LPCR_VRMASD_SHIFT;
> -    vsid |= (vrmasd << 4) & (SLB_VSID_L | SLB_VSID_LP);
> -    esid = SLB_ESID_V;
> -
> -    for (i = 0; i < PPC_PAGE_SIZES_MAX_SZ; i++) {
> -        const PPCHash64SegmentPageSizes *sps1 = &cpu->hash64_opts->sps[i];
> -
> -        if (!sps1->page_shift) {
> -            break;
> +    if (ppc_hash64_use_vrma(env)) {
> +        if (build_vrma_slbe(cpu, slb) == 0) {
> +            return;
>          }
> -
> -        if ((vsid & SLB_VSID_LLP_MASK) == sps1->slb_enc) {
> -            sps = sps1;
> -            break;
> -        }
> -    }
> -
> -    if (!sps) {
> -        error_report("Bad page size encoding esid 0x"TARGET_FMT_lx
> -                     " vsid 0x"TARGET_FMT_lx, esid, vsid);
> -        return;
>      }
>  
> -    slb->vsid = vsid;
> -    slb->esid = esid;
> -    slb->sps = sps;
> +    /* Otherwise, clear it to indicate error */
> +    slb->esid = slb->vsid = 0;
> +    slb->sps = NULL;
>  }
>  
>  void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
> @@ -1098,7 +1095,6 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
>      CPUPPCState *env = &cpu->env;
>  
>      env->spr[SPR_LPCR] = val & pcc->lpcr_mask;
> -    env->rmls = rmls_limit(cpu);
>      ppc_hash64_update_vrma(cpu);
>  }
>