Re: [PATCH v2 10/10] target/ppc: Only calculate RMLS derived RMA limit on demand

["Cédric Le Goater" <clg@kaod.org>]

On 1/7/20 5:48 AM, David Gibson 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.
> 
> 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 | 8 +++++---
>  2 files changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
> index 2de9e2fa2b..2a79b97bd8 100644
> --- a/target/ppc/cpu.h
> +++ b/target/ppc/cpu.h
> @@ -1075,7 +1075,6 @@ 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 e6f24be93e..170a78bd2e 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -842,8 +842,10 @@ 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 {
> @@ -1005,8 +1007,9 @@ hwaddr ppc_hash64_get_phys_page_debug(PowerPCCPU *cpu, target_ulong addr)
>                  return -1;
>              }
>          } else {
> +            target_ulong limit = rmls_limit(cpu);
>              /* Emulated old-style RMO mode, bounds check against RMLS */
> -            if (raddr >= env->rmls) {
> +            if (raddr >= limit) {
>                  return -1;
>              }
>              return raddr | env->spr[SPR_RMOR];
> @@ -1096,7 +1099,6 @@ 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);
>  }
>  
>