Re: [Qemu-devel] [PATCH v4] implementing victim TLB for QEMU system emulated TLB

[Peter Maydell]

On 3 February 2014 15:18, Xin Tong <address@hidden> wrote:
> This patch adds a victim TLB to the QEMU system mode TLB.

> @@ -264,8 +286,15 @@ void tlb_set_page(CPUArchState *env, target_ulong vaddr,
>                                              prot, &address);
>
>      index = (vaddr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
> -    env->iotlb[mmu_idx][index] = iotlb - vaddr;
>      te = &env->tlb_table[mmu_idx][index];
> +
> +    /* do not discard the translation in te, evict it into a victim tlb */
> +    unsigned vidx = env->vtlb_index++ % CPU_VTLB_SIZE;

Variable declarations should go at the start of a block.

> +/* macro to check the victim tlb */
> +#define VICTIM_TLB_HIT(ty)                                                   
>  \
> +({                                                                           
>  \
> +    /* we are about to do a page table walk. our last hope is the            
>  \
> +     * victim tlb. try to refill from the victim tlb before walking the      
>  \
> +     * page table. */                                                        
>  \
> +    int vidx;                                                                
>  \
> +    hwaddr tmpiotlb;                                                         
>  \
> +    CPUTLBEntry tmptlb;                                                      
>  \
> +    for (vidx = CPU_VTLB_SIZE; vidx >= 0; --vidx) {                          
>  \
> +        if (env->tlb_v_table[mmu_idx][vidx].ty == (addr & TARGET_PAGE_MASK)) 
> {\
> +            /* found entry in victim tlb, swap tlb and iotlb */              
>  \
> +            tmptlb = env->tlb_table[mmu_idx][index];                         
>  \
> +            env->tlb_table[mmu_idx][index] = 
> env->tlb_v_table[mmu_idx][vidx]; \
> +            env->tlb_v_table[mmu_idx][vidx] = tmptlb;                        
>  \
> +            tmpiotlb = env->iotlb[mmu_idx][index];                           
>  \
> +            env->iotlb[mmu_idx][index] = env->iotlb_v[mmu_idx][vidx];        
>  \
> +            env->iotlb_v[mmu_idx][vidx] = tmpiotlb;                          
>  \
> +            break;                                                           
>  \
> +        }                                                                    
>  \
> +    }                                                                        
>  \

This loop indexes off the end of the [vidx] arrays on its
first iteration, doesn't it?

thanks
-- PMM