Re: [Qemu-devel] [PATCH 1/2] cputlb: Use memset when flushing entries

[Aurelien Jarno <aurelien@aurel32.net>]

On Sat, Dec 07, 2013 at 10:44:51AM +1300, Richard Henderson wrote:
> The size of tlb_table is 4k on a 64-bit host.  For overwriting
> memory at this size, cacheline tricks can help.
> 
> Signed-off-by: Richard Henderson <rth@twiddle.net>
> ---
>  cputlb.c | 19 ++-----------------
>  1 file changed, 2 insertions(+), 17 deletions(-)
> 
> diff --git a/cputlb.c b/cputlb.c
> index fff0afb..d2da404 100644
> --- a/cputlb.c
> +++ b/cputlb.c
> @@ -33,13 +33,6 @@
>  /* statistics */
>  int tlb_flush_count;
>  
> -static const CPUTLBEntry s_cputlb_empty_entry = {
> -    .addr_read  = -1,
> -    .addr_write = -1,
> -    .addr_code  = -1,
> -    .addend     = -1,
> -};
> -
>  /* NOTE:
>   * If flush_global is true (the usual case), flush all tlb entries.
>   * If flush_global is false, flush (at least) all tlb entries not
> @@ -55,7 +48,6 @@ static const CPUTLBEntry s_cputlb_empty_entry = {
>  void tlb_flush(CPUArchState *env, int flush_global)
>  {
>      CPUState *cpu = ENV_GET_CPU(env);
> -    int i;
>  
>  #if defined(DEBUG_TLB)
>      printf("tlb_flush:\n");
> @@ -64,14 +56,7 @@ void tlb_flush(CPUArchState *env, int flush_global)
>         links while we are modifying them */
>      cpu->current_tb = NULL;
>  
> -    for (i = 0; i < CPU_TLB_SIZE; i++) {
> -        int mmu_idx;
> -
> -        for (mmu_idx = 0; mmu_idx < NB_MMU_MODES; mmu_idx++) {
> -            env->tlb_table[mmu_idx][i] = s_cputlb_empty_entry;
> -        }
> -    }
> -
> +    memset(env->tlb_table, -1, sizeof(env->tlb_table));
>      memset(env->tb_jmp_cache, 0, TB_JMP_CACHE_SIZE * sizeof (void *));
>  
>      env->tlb_flush_addr = -1;
> @@ -87,7 +72,7 @@ static inline void tlb_flush_entry(CPUTLBEntry *tlb_entry, target_ulong addr)
>                   (TARGET_PAGE_MASK | TLB_INVALID_MASK)) ||
>          addr == (tlb_entry->addr_code &
>                   (TARGET_PAGE_MASK | TLB_INVALID_MASK))) {
> -        *tlb_entry = s_cputlb_empty_entry;
> +        memset(tlb_entry, -1, sizeof(*tlb_entry));
>      }
>  }

Reviewed-by: Aurelien Jarno <aurelien@aurel32.net>

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net