Re: [Qemu-devel] passing translated address out in QEMU

[Xin Tong <xerox.time.tech@gmail.com>]

On Thu, Aug 23, 2012 at 7:57 PM, 陳韋任 (Wei-Ren Chen)
<chenwj@iis.sinica.edu.tw> wrote:
>> even that. is it possible to pass host virtual out. the fast path add
>> the addend to get host virtual ? so it must be in a register, most
>> likely eax in i386. what do you think would be the best way to get
>> that out ?
>
>   Take a look on comment on tcg_out_tlb_load (tcg/i386/tcg-target.c).
>
>    First argument register is loaded with the low part of the address.
>    In the TLB hit case, it has been adjusted as indicated by the TLB
>    and so is a host address.  In the TLB miss case, it continues to
>    hold a guest address.
>
> So I guess you can take "tcg_target_call_iarg_regs[0]" as host virtual
> address if software tlb hit.
>
>     /* TLB Hit.  */
>     tcg_out_qemu_ld_direct(s, data_reg, data_reg2,
>                            tcg_target_call_iarg_regs[0], 0, opc);
>
> As for how do you get host virtual address out, I think you can write
> a helper function logging those host virtual address into a file or
> something else, then insert a helper function call at the point of
> TLB hit.
>
> 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

That might be difficult. what i did was that i disabled inlined
translated and push the virt/phys address into 2 new fields in the cpu
structure in the call out lookup. because in the callout lookup we
have a handle to the cpu env.

not too sure how much impact inlined lookup has on the performance.
since i disabled it, next step i would just get rid of that piece of
generated assembly, as it is no good for icache ( generated for every
memory operation).

Xin