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

[陳韋任]

> > 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