Re: [Qemu-devel] [PATCH v2] cpu: implementing victim TLB for QEMU system emulated TLB

[Xin Tong]

Hi Max

Thank you for taking the time to review my patch

On Thu, Jan 23, 2014 at 2:44 PM, Max Filippov <address@hidden> wrote:
> Hi Xin,
>
> On Thu, Jan 23, 2014 at 11:49 PM, Xin Tong <address@hidden> wrote:
>
> [...]
>
>> diff --git a/cputlb.c b/cputlb.c
>> index b533f3f..03a048a 100644
>> --- a/cputlb.c
>> +++ b/cputlb.c
>> @@ -34,6 +34,22 @@
>>  /* statistics */
>>  int tlb_flush_count;
>>
>> +/* swap the 2 given TLB entries as well as their corresponding IOTLB */
>> +inline void swap_tlb(CPUTLBEntry *te, CPUTLBEntry *se, hwaddr *iote,
>> +                     hwaddr *iose)
>> +{
>> +   hwaddr iotmp;
>> +   CPUTLBEntry t;
>> +   /* swap iotlb */
>> +   iotmp = *iote;
>> +   *iote = *iose;
>> +   *iose = iotmp;
>> +   /* swap tlb */
>> +   memcpy(&t, te, sizeof(CPUTLBEntry));
>> +   memcpy(te, se, sizeof(CPUTLBEntry));
>> +   memcpy(se, &t, sizeof(CPUTLBEntry));
>
> You could use assignment operator, it works:
>     t = *te;
>     *te = *se;
>     *se = t;
>
i see, will fix in patch v3.

> Also all users of this function are inline functions from softmmu_template.h
> Could this function be a static inline function in that file too?

I am following where tlb_fill and tlb_flush are placed. Also, the
softmmu_template.h is included more than once, would put the swap_tlb
in softmmu_template.h result in multiple definitions ?
>
>> +}
>
> [...]
>
>> --- a/include/exec/softmmu_template.h
>> +++ b/include/exec/softmmu_template.h
>> @@ -141,6 +141,7 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, 
>> target_ulong addr, int mmu_idx,
>>      target_ulong tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
>>      uintptr_t haddr;
>>      DATA_TYPE res;
>> +    int vtlb_idx;
>>
>>      /* Adjust the given return address.  */
>>      retaddr -= GETPC_ADJ;
>> @@ -153,7 +154,24 @@ WORD_TYPE helper_le_ld_name(CPUArchState *env, 
>> target_ulong addr, int mmu_idx,
>>              do_unaligned_access(env, addr, READ_ACCESS_TYPE, mmu_idx, 
>> retaddr);
>>          }
>>  #endif
>> -        tlb_fill(env, addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
>> +        /* 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. */
>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].ADDR_READ
>
> Is it ADDR_READ or addr_read, as it is called in other places?

I am following  target_ulong tlb_addr =
env->tlb_table[mmu_idx][index].ADDR_READ; in the same function. I am
not sure i get what you mean.

>
>> +                == (addr & TARGET_PAGE_MASK)) {
>> +                /* found entry in victim tlb */
>> +                swap_tlb(&env->tlb_table[mmu_idx][index],
>> +                         &env->tlb_v_table[mmu_idx][vtlb_idx],
>> +                         &env->iotlb[mmu_idx][index],
>> +                         &env->iotlb_v[mmu_idx][vtlb_idx]);
>> +                break;
>> +            }
>> +        }
>> +        /* miss victim tlb */
>> +        if (vtlb_idx < 0) {
>> +            tlb_fill(env, addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
>> +        }
>>          tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
>>      }
>>
>> @@ -223,6 +241,7 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, 
>> target_ulong addr, int mmu_idx,
>>      target_ulong tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
>>      uintptr_t haddr;
>>      DATA_TYPE res;
>> +    int vtlb_idx;
>>
>>      /* Adjust the given return address.  */
>>      retaddr -= GETPC_ADJ;
>> @@ -235,7 +254,24 @@ WORD_TYPE helper_be_ld_name(CPUArchState *env, 
>> target_ulong addr, int mmu_idx,
>>              do_unaligned_access(env, addr, READ_ACCESS_TYPE, mmu_idx, 
>> retaddr);
>>          }
>>  #endif
>> -        tlb_fill(env, addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
>> +        /* 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. */
>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].ADDR_READ
>> +                == (addr & TARGET_PAGE_MASK)) {
>> +                /* found entry in victim tlb */
>> +                swap_tlb(&env->tlb_table[mmu_idx][index],
>> +                         &env->tlb_v_table[mmu_idx][vtlb_idx],
>> +                         &env->iotlb[mmu_idx][index],
>> +                         &env->iotlb_v[mmu_idx][vtlb_idx]);
>> +                break;
>> +            }
>> +        }
>
> It could be a good inline function.
>
>> +        /* miss victim tlb */
>> +        if (vtlb_idx < 0) {
>> +            tlb_fill(env, addr, READ_ACCESS_TYPE, mmu_idx, retaddr);
>> +        }
>>          tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
>>      }
>>
>> @@ -342,6 +378,7 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
>> addr, DATA_TYPE val,
>>      int index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
>>      target_ulong tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
>>      uintptr_t haddr;
>> +    int vtlb_idx;
>>
>>      /* Adjust the given return address.  */
>>      retaddr -= GETPC_ADJ;
>> @@ -354,7 +391,24 @@ void helper_le_st_name(CPUArchState *env, target_ulong 
>> addr, DATA_TYPE val,
>>              do_unaligned_access(env, addr, 1, mmu_idx, retaddr);
>>          }
>>  #endif
>> -        tlb_fill(env, addr, 1, mmu_idx, retaddr);
>> +        /* 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. */
>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].addr_write
>> +                == (addr & TARGET_PAGE_MASK)) {
>> +                /* found entry in victim tlb */
>> +                swap_tlb(&env->tlb_table[mmu_idx][index],
>> +                         &env->tlb_v_table[mmu_idx][vtlb_idx],
>> +                         &env->iotlb[mmu_idx][index],
>> +                         &env->iotlb_v[mmu_idx][vtlb_idx]);
>> +                break;
>> +            }
>> +        }
>> +        /* miss victim tlb */
>> +        if (vtlb_idx < 0) {
>> +            tlb_fill(env, addr, 1, mmu_idx, retaddr);
>> +        }
>>          tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
>>      }
>>
>> @@ -418,6 +472,7 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
>> addr, DATA_TYPE val,
>>      int index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
>>      target_ulong tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
>>      uintptr_t haddr;
>> +    int vtlb_idx;
>>
>>      /* Adjust the given return address.  */
>>      retaddr -= GETPC_ADJ;
>> @@ -430,7 +485,24 @@ void helper_be_st_name(CPUArchState *env, target_ulong 
>> addr, DATA_TYPE val,
>>              do_unaligned_access(env, addr, 1, mmu_idx, retaddr);
>>          }
>>  #endif
>> -        tlb_fill(env, addr, 1, mmu_idx, retaddr);
>> +        /* 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. */
>> +        for (vtlb_idx = CPU_VTLB_SIZE; vtlb_idx >= 0; --vtlb_idx) {
>> +            if (env->tlb_v_table[mmu_idx][vtlb_idx].addr_write
>> +                == (addr & TARGET_PAGE_MASK)) {
>> +                /* found entry in victim tlb */
>> +                swap_tlb(&env->tlb_table[mmu_idx][index],
>> +                         &env->tlb_v_table[mmu_idx][vtlb_idx],
>> +                         &env->iotlb[mmu_idx][index],
>> +                         &env->iotlb_v[mmu_idx][vtlb_idx]);
>> +                break;
>> +            }
>> +        }
>
> It could be a good inline function too.

One way is to define the victim tlb lookup code in a C function which
gets called before tlb_fill. but i need the ADDR_READ and addr_write
macros.
>
>> +        /* miss victim tlb */
>> +        if (vtlb_idx < 0) {
>> +            tlb_fill(env, addr, 1, mmu_idx, retaddr);
>> +        }
>>          tlb_addr = env->tlb_table[mmu_idx][index].addr_write;
>>      }
>
> --
> Thanks.
> -- Max