Re: [Qemu-devel] qemu softmmu inlined lookup sequence

[Blue Swirl]

On Tue, Apr 17, 2012 at 05:40, Xin Tong <address@hidden> wrote:
> that is possible. but if that is the case, why not split the tlb
> walking and the tlb fill ? can anyone please confirm ?

I sent a patch earlier that did something like that but it wasn't very
successful:
http://lists.nongnu.org/archive/html/qemu-devel/2012-04/msg00992.html

>
> Xin
>
>
> 2012/4/16 陳韋任 <address@hidden>:
>>> > If TLB miss, it will call something like __ldb_mmu (b). __ldb_mmu will 
>>> > try to
>>> > walk guest page table, then fill TLB entry if page table hit, or raise a 
>>> > guest
>>> > page fault exception if page table miss.
>>>
>>> Yep. that is what i was taught. the sequence of code above is an
>>> inlined assembly for walking the TLB.  In the __ldx_mmu, the tlb is
>>> walked again ? why ?
>>>
>>>     int index, shift;
>>>     target_phys_addr_t ioaddr;
>>>     unsigned long addend;
>>>     target_ulong tlb_addr, addr1, addr2;
>>>
>>>     index = (addr >> TARGET_PAGE_BITS) & (CPU_TLB_SIZE - 1);
>>>  redo:
>>>     tlb_addr = env->tlb_table[mmu_idx][index].ADDR_READ;
>>>     if ((addr & TARGET_PAGE_MASK) == (tlb_addr & (TARGET_PAGE_MASK |
>>> TLB_INVALID_MASK))) {
>>>     ...
>>>  }
>>>
>>>   ...
>>>   ...
>>>   fill_tlb()
>>>   ...
>>>
>>> }
>>
>>  Perhaps __ldb_mmu is not only called in the TLB lookup sequence, I guess.
>> But I am not sure of it.
>>
>> Regards,
>> chenwj
>>
>>
>> --
>> Wei-Ren Chen (陳韋任)
>> Computer Systems Lab, Institute of Information Science,
>> Academia Sinica, Taiwan (R.O.C.)
>> Tel:886-2-2788-3799 #1667
>> Homepage: http://people.cs.nctu.edu.tw/~chenwj
>