Re: [Qemu-devel] [PATCH v2 1/6] cputlb: Add functions for flushing TLB for a single MMU index

[Edgar E. Iglesias]

On Fri, Aug 14, 2015 at 11:41:14AM +0100, Peter Maydell wrote:
> Guest CPU TLB maintenance operations may be sufficiently
> specialized to only need to flush TLB entries corresponding
> to a particular MMU index. Implement cputlb functions for
> this, to avoid the inefficiency of flushing TLB entries
> which we don't need to.
> 
> Signed-off-by: Peter Maydell <address@hidden>

Reviewed-by: Edgar E. Iglesias <address@hidden>




> ---
>  cputlb.c                | 97 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  include/exec/exec-all.h | 47 ++++++++++++++++++++++++
>  2 files changed, 144 insertions(+)
> 
> diff --git a/cputlb.c b/cputlb.c
> index a506086..4bc6c24 100644
> --- a/cputlb.c
> +++ b/cputlb.c
> @@ -69,6 +69,47 @@ void tlb_flush(CPUState *cpu, int flush_global)
>      tlb_flush_count++;
>  }
>  
> +static inline void v_tlb_flush_by_mmuidx(CPUState *cpu, va_list argp)
> +{
> +    CPUArchState *env = cpu->env_ptr;
> +
> +#if defined(DEBUG_TLB)
> +    printf("tlb_flush_by_mmuidx:");
> +#endif
> +    /* must reset current TB so that interrupts cannot modify the
> +       links while we are modifying them */
> +    cpu->current_tb = NULL;
> +
> +    for (;;) {
> +        int mmu_idx = va_arg(argp, int);
> +
> +        if (mmu_idx < 0) {
> +            break;
> +        }
> +
> +#if defined(DEBUG_TLB)
> +        printf(" %d", mmu_idx);
> +#endif
> +
> +        memset(env->tlb_table[mmu_idx], -1, sizeof(env->tlb_table[0]));
> +        memset(env->tlb_v_table[mmu_idx], -1, sizeof(env->tlb_v_table[0]));
> +    }
> +
> +#if defined(DEBUG_TLB)
> +    printf("\n");
> +#endif
> +
> +    memset(cpu->tb_jmp_cache, 0, sizeof(cpu->tb_jmp_cache));
> +}
> +
> +void tlb_flush_by_mmuidx(CPUState *cpu, ...)
> +{
> +    va_list argp;
> +    va_start(argp, cpu);
> +    v_tlb_flush_by_mmuidx(cpu, argp);
> +    va_end(argp);
> +}
> +
>  static inline void tlb_flush_entry(CPUTLBEntry *tlb_entry, target_ulong addr)
>  {
>      if (addr == (tlb_entry->addr_read &
> @@ -121,6 +162,62 @@ void tlb_flush_page(CPUState *cpu, target_ulong addr)
>      tb_flush_jmp_cache(cpu, addr);
>  }
>  
> +void tlb_flush_page_by_mmuidx(CPUState *cpu, target_ulong addr, ...)
> +{
> +    CPUArchState *env = cpu->env_ptr;
> +    int i, k;
> +    va_list argp;
> +
> +    va_start(argp, addr);
> +
> +#if defined(DEBUG_TLB)
> +    printf("tlb_flush_page_by_mmu_idx: " TARGET_FMT_lx, addr);
> +#endif
> +    /* Check if we need to flush due to large pages.  */
> +    if ((addr & env->tlb_flush_mask) == env->tlb_flush_addr) {
> +#if defined(DEBUG_TLB)
> +        printf(" forced full flush ("
> +               TARGET_FMT_lx "/" TARGET_FMT_lx ")\n",
> +               env->tlb_flush_addr, env->tlb_flush_mask);
> +#endif
> +        v_tlb_flush_by_mmuidx(cpu, argp);
> +        va_end(argp);
> +        return;
> +    }
> +    /* must reset current TB so that interrupts cannot modify the
> +       links while we are modifying them */
> +    cpu->current_tb = NULL;
> +
> +    addr &= TARGET_PAGE_MASK;
> +    i = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
> +
> +    for (;;) {
> +        int mmu_idx = va_arg(argp, int);
> +
> +        if (mmu_idx < 0) {
> +            break;
> +        }
> +
> +#if defined(DEBUG_TLB)
> +        printf(" %d", mmu_idx);
> +#endif
> +
> +        tlb_flush_entry(&env->tlb_table[mmu_idx][i], addr);
> +
> +        /* check whether there are vltb entries that need to be flushed */
> +        for (k = 0; k < CPU_VTLB_SIZE; k++) {
> +            tlb_flush_entry(&env->tlb_v_table[mmu_idx][k], addr);
> +        }
> +    }
> +    va_end(argp);
> +
> +#if defined(DEBUG_TLB)
> +    printf("\n");
> +#endif
> +
> +    tb_flush_jmp_cache(cpu, addr);
> +}
> +
>  /* update the TLBs so that writes to code in the virtual page 'addr'
>     can be detected */
>  void tlb_protect_code(ram_addr_t ram_addr)
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index a6fce04..4933683 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -96,8 +96,46 @@ bool qemu_in_vcpu_thread(void);
>  void cpu_reload_memory_map(CPUState *cpu);
>  void tcg_cpu_address_space_init(CPUState *cpu, AddressSpace *as);
>  /* cputlb.c */
> +/**
> + * tlb_flush_page:
> + * @cpu: CPU whose TLB should be flushed
> + * @addr: virtual address of page to be flushed
> + *
> + * Flush one page from the TLB of the specified CPU, for all
> + * MMU indexes.
> + */
>  void tlb_flush_page(CPUState *cpu, target_ulong addr);
> +/**
> + * tlb_flush:
> + * @cpu: CPU whose TLB should be flushed
> + * @flush_global: ignored
> + *
> + * Flush the entire TLB for the specified CPU.
> + * The flush_global flag is in theory an indicator of whether the whole
> + * TLB should be flushed, or only those entries not marked global.
> + * In practice QEMU does not implement any global/not global flag for
> + * TLB entries, and the argument is ignored.
> + */
>  void tlb_flush(CPUState *cpu, int flush_global);
> +/**
> + * tlb_flush_page_by_mmuidx:
> + * @cpu: CPU whose TLB should be flushed
> + * @addr: virtual address of page to be flushed
> + * @...: list of MMU indexes to flush, terminated by a negative value
> + *
> + * Flush one page from the TLB of the specified CPU, for the specified
> + * MMU indexes.
> + */
> +void tlb_flush_page_by_mmuidx(CPUState *cpu, target_ulong addr, ...);
> +/**
> + * tlb_flush_by_mmuidx:
> + * @cpu: CPU whose TLB should be flushed
> + * @...: list of MMU indexes to flush, terminated by a negative value
> + *
> + * Flush all entries from the TLB of the specified CPU, for the specified
> + * MMU indexes.
> + */
> +void tlb_flush_by_mmuidx(CPUState *cpu, ...);
>  void tlb_set_page(CPUState *cpu, target_ulong vaddr,
>                    hwaddr paddr, int prot,
>                    int mmu_idx, target_ulong size);
> @@ -115,6 +153,15 @@ static inline void tlb_flush_page(CPUState *cpu, 
> target_ulong addr)
>  static inline void tlb_flush(CPUState *cpu, int flush_global)
>  {
>  }
> +
> +static inline void tlb_flush_page_by_mmuidx(CPUState *cpu,
> +                                            target_ulong addr, ...)
> +{
> +}
> +
> +static inline void tlb_flush_by_mmuidx(CPUState *cpu, ...)
> +{
> +}
>  #endif
>  
>  #define CODE_GEN_ALIGN           16 /* must be >= of the size of a icache 
> line */
> -- 
> 1.9.1
>