Re: [Qemu-devel] When the tlb_fill will be called from generated code?

[陳韋任]

Hi, Jan

> You can find the answer yourself: Load qemu into gdb, set a breakpoint
> on that function and let it run. If you want to catch only the retaddr
> == NULL case, make the breakpoint conditional.

  Thanks for your tip. I see when retaddr != NULL, then the calling
sequence of tlb_fill might be something like (take i386 guest for
example):

  - __stl_mmu/__ldl_mmu -> tlb_fill

  - helper_ljmp_protected -> load_segment -> ldl_kernel -> __ldl_mmu

I am not sure when/where __stl_mmu/__ldl_mmu are used. I do set
breakpoint on __stl_mmu/__ldl_mmu, but the backtrace can only show
something like,

#0  __stl_mmu (addr=196608, val=0, mmu_idx=0) at 
/tmp/chenwj/temp/qemu-0.13.0/softmmu_template.h:228
#1  0x00000000400028e1 in ?? ()
#2  0x00000000000000b4 in ?? ()
#3  0xecc68ff412fa4137 in ?? ()
#4  0x0000000000000000 in ?? ()

When retaddr == NULL, then the calling sequence of tlb_fill is,

  tb_find_slow -> get_page_addr_code -> ldub_code -> __ldb_cmmu

I can only guest the b in __ldb_cmmu means load byte, but I can't
figure out what's the difference between _cmmu and _mmu. Could you
give me some hint? Thanks!


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