> I am studying QEMU, I would like to know that Is QEMU TB lookup based on
> guest system virtual address or physical address ?
QEMU lookups TB in two steps:
tb_find_fast (exec.c):
It'll try to use guest virtual address (pc) to index tb_jmp_cache.
tb = env->tb_jmp_cache[tb_jmp_cache_hash_func(pc)];
Then it'll check if there is a hit or not. Also check the finded TB
is valid or not.
if (unlikely(!tb || tb->pc != pc || tb->cs_base != cs_base ||
tb->flags != flags)) {
tb = tb_find_slow(env, pc, cs_base, flags);
}
tb_find_slow (exec.c):
If tb_find_fast fail to find a TB by using guest virtual address (pc),
then it comes to tb_find_slow. tb_find_slow use pc's corresponding
guest physical address to index tb_phys_hash.
/* find translated block using physical mappings */
phys_pc = get_page_addr_code(env, pc);
phys_page1 = phys_pc & TARGET_PAGE_MASK;
h = tb_phys_hash_func(phys_pc);
ptb1 = &tb_phys_hash[h];
Then it'll check if there is a hit or not. Also check the finded TB
is valid or not. If tb_phys_hash hit and the finded TB is valid, then
it goes to lable found:
found:
/* we add the TB in the virtual pc hash table */
env->tb_jmp_cache[tb_jmp_cache_hash_func(pc)] = tb;
Otherwise, it goes to lable not_found:
not_found:
/* if no translated code available, then translate it now */
tb = tb_gen_code(env, pc, cs_base, flags, 0);
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
