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

[陳韋任]

> what does the inline sequence look like ? what kind of things (other
> than refill tlb) performed in callout but not the inlined sequence ?

  What do you mean by the inline sequence, the host binary? If so, 

---
 ---- 0xe86c8
 mov_i32 tmp2,edi
 qemu_ld8u tmp0,tmp2,$0x0
 ext8u_i32 tmp12,tmp0
 movi_i32 tmp13,$0xffffff00
 and_i32 edx,edx,tmp13
 or_i32 edx,edx,tmp12

OUT: [size=172]
0x40000ce0:  mov    0x1c(%r14),%ebp
0x40000ce4:  mov    %ebp,%esi               <--- (a)
0x40000ce6:  mov    %ebp,%edi
0x40000ce8:  shr    $0x7,%esi               
0x40000ceb:  and    $0xfffff000,%edi        
0x40000cf1:  and    $0x1fe0,%esi            
0x40000cf7:  lea    0x348(%r14,%rsi,1),%rsi 
0x40000cff:  cmp    (%rsi),%edi             
0x40000d01:  mov    %ebp,%edi               
0x40000d03:  jne    0x40000d0e              
0x40000d05:  add    0x10(%rsi),%rdi         
0x40000d09:  movzbl (%rdi),%ebp             
0x40000d0c:  jmp    0x40000d18
0x40000d0e:  xor    %esi,%esi               
0x40000d10:  callq  0x54cf8e                <--- (b)
0x40000d15:  movzbl %al,%ebp                
0x40000d18:  movzbl %bpl,%ebp
0x40000d1c:  mov    0x8(%r14),%ebx
---

  The code between (a) and (b) is (almost) what TLB lookup hit/miss looks like.
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.  

HTH,
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