Re: [Qemu-devel] [PATCH 1/6] pseries: Minor cleanups to HPT management hypercalls

[Suraj Jitindar Singh <sjitindarsingh@gmail.com>]

On Thu, 2017-02-23 at 13:09 +1100, David Gibson wrote:
>  * Standardize on 'ptex' instead of 'pte_index' for HPTE index
> variables
>    for consistency and brevity
>  * Avoid variables named 'index'; shadowing index(3) from libc can
> lead to
>    surprising bugs if the variable is removed, because compiler
> errors
>    might not appear for remaining references
>  * Clarify index calculations in h_enter() - we have two cases,
> H_EXACT
>    where the exact HPTE slot is given, and !H_EXACT where we search
> for
>    an empty slot within the hash bucket.  Make the calculation more
>    consistent between the cases.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  hw/ppc/spapr_hcall.c | 58 +++++++++++++++++++++++++-----------------
> ----------
>  1 file changed, 28 insertions(+), 30 deletions(-)
> 
> diff --git a/hw/ppc/spapr_hcall.c b/hw/ppc/spapr_hcall.c
> index 42d20e0..3298a14 100644
> --- a/hw/ppc/spapr_hcall.c
> +++ b/hw/ppc/spapr_hcall.c
> @@ -47,12 +47,12 @@ static bool has_spr(PowerPCCPU *cpu, int spr)
>      return cpu->env.spr_cb[spr].name != NULL;
>  }
>  
> -static inline bool valid_pte_index(CPUPPCState *env, target_ulong
> pte_index)
> +static inline bool valid_ptex(PowerPCCPU *cpu, target_ulong ptex)
>  {
>      /*
>       * hash value/pteg group index is normalized by htab_mask
>       */
> -    if (((pte_index & ~7ULL) / HPTES_PER_GROUP) & ~env->htab_mask) {
> +    if (((ptex & ~7ULL) / HPTES_PER_GROUP) & ~cpu->env.htab_mask) {
>          return false;
>      }
>      return true;
> @@ -77,14 +77,13 @@ static bool is_ram_address(sPAPRMachineState
> *spapr, hwaddr addr)
>  static target_ulong h_enter(PowerPCCPU *cpu, sPAPRMachineState
> *spapr,
>                              target_ulong opcode, target_ulong *args)
>  {
> -    CPUPPCState *env = &cpu->env;
>      target_ulong flags = args[0];
> -    target_ulong pte_index = args[1];
> +    target_ulong ptex = args[1];
>      target_ulong pteh = args[2];
>      target_ulong ptel = args[3];
>      unsigned apshift;
>      target_ulong raddr;
> -    target_ulong index;
> +    target_ulong slot;
>      uint64_t token;
>  
>      apshift = ppc_hash64_hpte_page_shift_noslb(cpu, pteh, ptel);
> @@ -116,25 +115,26 @@ static target_ulong h_enter(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>  
>      pteh &= ~0x60ULL;
>  
> -    if (!valid_pte_index(env, pte_index)) {
> +    if (!valid_ptex(cpu, ptex)) {
>          return H_PARAMETER;
>      }
>  
> -    index = 0;
> +    slot = ptex & 7ULL;
> +    ptex = ptex & ~7ULL;
> +
>      if (likely((flags & H_EXACT) == 0)) {
> -        pte_index &= ~7ULL;
> -        token = ppc_hash64_start_access(cpu, pte_index);
> -        for (; index < 8; index++) {
> -            if (!(ppc_hash64_load_hpte0(cpu, token, index) &
> HPTE64_V_VALID)) {
> +        token = ppc_hash64_start_access(cpu, ptex);
> +        for (slot = 0; slot < 8; slot++) {
> +            if (!(ppc_hash64_load_hpte0(cpu, token, slot) &
> HPTE64_V_VALID)) {
>                  break;
>              }
>          }
>          ppc_hash64_stop_access(cpu, token);
> -        if (index == 8) {
> +        if (slot == 8) {
>              return H_PTEG_FULL;
>          }
>      } else {
> -        token = ppc_hash64_start_access(cpu, pte_index);
> +        token = ppc_hash64_start_access(cpu, ptex);
>          if (ppc_hash64_load_hpte0(cpu, token, 0) & HPTE64_V_VALID) {
>              ppc_hash64_stop_access(cpu, token);
>              return H_PTEG_FULL;
> @@ -142,10 +142,9 @@ static target_ulong h_enter(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>          ppc_hash64_stop_access(cpu, token);
>      }
>  
> -    ppc_hash64_store_hpte(cpu, pte_index + index,
> -                          pteh | HPTE64_V_HPTE_DIRTY, ptel);
> +    ppc_hash64_store_hpte(cpu, ptex + slot, pteh |
> HPTE64_V_HPTE_DIRTY, ptel);
>  
> -    args[0] = pte_index + index;
> +    args[0] = ptex + slot;
>      return H_SUCCESS;
>  }
>  
> @@ -161,11 +160,10 @@ static RemoveResult remove_hpte(PowerPCCPU
> *cpu, target_ulong ptex,
>                                  target_ulong flags,
>                                  target_ulong *vp, target_ulong *rp)
>  {
> -    CPUPPCState *env = &cpu->env;
>      uint64_t token;
>      target_ulong v, r;
>  
> -    if (!valid_pte_index(env, ptex)) {
> +    if (!valid_ptex(cpu, ptex)) {
>          return REMOVE_PARM;
>      }
>  
> @@ -191,11 +189,11 @@ static target_ulong h_remove(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>  {
>      CPUPPCState *env = &cpu->env;
>      target_ulong flags = args[0];
> -    target_ulong pte_index = args[1];
> +    target_ulong ptex = args[1];
>      target_ulong avpn = args[2];
>      RemoveResult ret;
>  
> -    ret = remove_hpte(cpu, pte_index, avpn, flags,
> +    ret = remove_hpte(cpu, ptex, avpn, flags,
>                        &args[0], &args[1]);
>  
>      switch (ret) {
> @@ -291,16 +289,16 @@ static target_ulong h_protect(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>  {
>      CPUPPCState *env = &cpu->env;
>      target_ulong flags = args[0];
> -    target_ulong pte_index = args[1];
> +    target_ulong ptex = args[1];
>      target_ulong avpn = args[2];
>      uint64_t token;
>      target_ulong v, r;
>  
> -    if (!valid_pte_index(env, pte_index)) {
> +    if (!valid_ptex(cpu, ptex)) {
>          return H_PARAMETER;
>      }
>  
> -    token = ppc_hash64_start_access(cpu, pte_index);
> +    token = ppc_hash64_start_access(cpu, ptex);
>      v = ppc_hash64_load_hpte0(cpu, token, 0);
>      r = ppc_hash64_load_hpte1(cpu, token, 0);
>      ppc_hash64_stop_access(cpu, token);
> @@ -315,13 +313,13 @@ static target_ulong h_protect(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>      r |= (flags << 55) & HPTE64_R_PP0;
>      r |= (flags << 48) & HPTE64_R_KEY_HI;
>      r |= flags & (HPTE64_R_PP | HPTE64_R_N | HPTE64_R_KEY_LO);
> -    ppc_hash64_store_hpte(cpu, pte_index,
> +    ppc_hash64_store_hpte(cpu, ptex,
>                            (v & ~HPTE64_V_VALID) |
> HPTE64_V_HPTE_DIRTY, 0);
> -    ppc_hash64_tlb_flush_hpte(cpu, pte_index, v, r);
> +    ppc_hash64_tlb_flush_hpte(cpu, ptex, v, r);
>      /* Flush the tlb */
>      check_tlb_flush(env, true);
>      /* Don't need a memory barrier, due to qemu's global lock */
> -    ppc_hash64_store_hpte(cpu, pte_index, v | HPTE64_V_HPTE_DIRTY,
> r);
> +    ppc_hash64_store_hpte(cpu, ptex, v | HPTE64_V_HPTE_DIRTY, r);
>      return H_SUCCESS;
>  }
>  
> @@ -330,21 +328,21 @@ static target_ulong h_read(PowerPCCPU *cpu,
> sPAPRMachineState *spapr,
>  {
>      CPUPPCState *env = &cpu->env;
>      target_ulong flags = args[0];
> -    target_ulong pte_index = args[1];
> +    target_ulong ptex = args[1];
>      uint8_t *hpte;
>      int i, ridx, n_entries = 1;
>  
> -    if (!valid_pte_index(env, pte_index)) {
> +    if (!valid_ptex(cpu, ptex)) {
>          return H_PARAMETER;
>      }
>  
>      if (flags & H_READ_4) {
>          /* Clear the two low order bits */
> -        pte_index &= ~(3ULL);
> +        ptex &= ~(3ULL);
>          n_entries = 4;
>      }
>  
> -    hpte = env->external_htab + (pte_index * HASH_PTE_SIZE_64);
> +    hpte = env->external_htab + (ptex * HASH_PTE_SIZE_64);
>  
>      for (i = 0, ridx = 0; i < n_entries; i++) {
>          args[ridx++] = ldq_p(hpte);
I wholeheartedly agree with this rename.

Reviewed-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>