Re: [Qemu-devel] [PATCH 26/32] ppc: Speed up dcbz

[David Gibson]

On Wed, Jul 27, 2016 at 08:21:20AM +1000, Benjamin Herrenschmidt wrote:
> Use tlb_vaddr_to_host to do a fast path single translate for
> the whole cache line. Also make the reservation check match
> the entire range.
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> ---
>  target-ppc/mem_helper.c | 46 +++++++++++++++++++++++++---------------------
>  target-ppc/translate.c  | 11 ++++-------
>  2 files changed, 29 insertions(+), 28 deletions(-)
> 
> diff --git a/target-ppc/mem_helper.c b/target-ppc/mem_helper.c
> index 92a594c..6548715 100644
> --- a/target-ppc/mem_helper.c
> +++ b/target-ppc/mem_helper.c
> @@ -141,35 +141,39 @@ void helper_stsw(CPUPPCState *env, target_ulong addr, 
> uint32_t nb,
>      }
>  }
>  
> -static void do_dcbz(CPUPPCState *env, target_ulong addr, int 
> dcache_line_size,
> -                    uintptr_t raddr)
> +void helper_dcbz(CPUPPCState *env, target_ulong addr, uint32_t opcode)
>  {
> -    int i;
> -
> -    addr &= ~(dcache_line_size - 1);
> -    for (i = 0; i < dcache_line_size; i += 4) {
> -        cpu_stl_data_ra(env, addr + i, 0, raddr);
> -    }
> -    if (env->reserve_addr == addr) {
> -        env->reserve_addr = (target_ulong)-1ULL;
> -    }
> -}
> -
> -void helper_dcbz(CPUPPCState *env, target_ulong addr, uint32_t is_dcbzl)
> -{
> -    int dcbz_size = env->dcache_line_size;
> +    target_ulong mask, dcbz_size = env->dcache_line_size;
> +    uint32_t i;
> +    void *haddr;
>  
>  #if defined(TARGET_PPC64)
> -    if (!is_dcbzl &&
> -        (env->excp_model == POWERPC_EXCP_970) &&
> -        ((env->spr[SPR_970_HID5] >> 7) & 0x3) == 1) {
> +    /* Check for dcbz vs dcbzl on 970 */
> +    if (env->excp_model == POWERPC_EXCP_970 &&
> +        !(opcode & 0x00200000) && ((env->spr[SPR_970_HID5] >> 7) & 0x3) == 
> 1) {
>          dcbz_size = 32;
>      }
>  #endif
>  
> -    /* XXX add e500mc support */
> +    /* Align address */
> +    mask = ~(dcbz_size - 1);
> +    addr &= mask;
> +
> +    /* Check reservation */
> +    if ((env->reserve_addr & mask) == (addr & mask))  {
> +        env->reserve_addr = (target_ulong)-1ULL;
> +    }
>  
> -    do_dcbz(env, addr, dcbz_size, GETPC());
> +    /* Try fast path translate */
> +    haddr = tlb_vaddr_to_host(env, addr, MMU_DATA_STORE, env->dmmu_idx);

It worries me slightly that this doesn't take any length to verify.  I
guess it's ok in practice, because memory blocks will always be at
least cache line size aligned.

> +    if (haddr) {
> +        memset(haddr, 0, dcbz_size);
> +    } else {
> +        /* Slow path */
> +        for (i = 0; i < dcbz_size; i += 8) {
> +            cpu_stq_data_ra(env, addr + i, 0, GETPC());
> +        }
> +    }
>  }
>  
>  void helper_icbi(CPUPPCState *env, target_ulong addr)
> diff --git a/target-ppc/translate.c b/target-ppc/translate.c
> index 57a891b..5288e02 100644
> --- a/target-ppc/translate.c
> +++ b/target-ppc/translate.c
> @@ -3851,18 +3851,15 @@ static void gen_dcbtls(DisasContext *ctx)
>  static void gen_dcbz(DisasContext *ctx)
>  {
>      TCGv tcgv_addr;
> -    TCGv_i32 tcgv_is_dcbzl;
> -    int is_dcbzl = ctx->opcode & 0x00200000 ? 1 : 0;
> +    TCGv_i32 tcgv_op;
>  
>      gen_set_access_type(ctx, ACCESS_CACHE);
>      tcgv_addr = tcg_temp_new();
> -    tcgv_is_dcbzl = tcg_const_i32(is_dcbzl);
> -
> +    tcgv_op = tcg_const_i32(ctx->opcode & 0x03FF000);
>      gen_addr_reg_index(ctx, tcgv_addr);
> -    gen_helper_dcbz(cpu_env, tcgv_addr, tcgv_is_dcbzl);
> -
> +    gen_helper_dcbz(cpu_env, tcgv_addr, tcgv_op);
>      tcg_temp_free(tcgv_addr);
> -    tcg_temp_free_i32(tcgv_is_dcbzl);
> +    tcg_temp_free_i32(tcgv_op);
>  }
>  
>  /* dst / dstt */

-- 
David Gibson                    | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au  | minimalist, thank you.  NOT _the_ _other_
                                | _way_ _around_!
http://www.ozlabs.org/~dgibson

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