On Mon, Apr 16, 2012 at 10:51 PM, 陳韋任 <che...@iis.sinica.edu.tw> wrote:
>> 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 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))) {
> 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.
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()
...
}
>
> 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
