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

[Steven <wangwangkang@gmail.com>]

Hi, Xin,
Try Max's patch
http://lists.gnu.org/archive/html/qemu-devel/2012-08/msg03226.html

I used it to get all the guest virtual address because this patch
disable the fast mmu path.

Steven

On Thu, Aug 23, 2012 at 12:18 PM, Xin Tong <xerox.time.tech@gmail.com> wrote:
> On Thu, Aug 23, 2012 at 8:52 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On 23 August 2012 16:34, Xin Tong <xerox.time.tech@gmail.com> wrote:
>>> I am emulating arm on x86. i want to track the virt and physical
>>> address of last memory operation. so i put 2 fields in the CPUState
>>> and make tcg_global_mem_new_i32 on them Therefore, before every
>>> translation i generate code to save the virtual address as follow:
>>>
>>> static inline void gen_st32(TCGv val, TCGv addr, int index)
>>> {
>>>     tcg_gen_mov_i32(cpu_last_vaddr, addr);
>>>     tcg_gen_qemu_st32(val, addr, index);
>>>    // tcg_gen_mov_i32(cpu_last_paddr, addr);
>>>     tcg_temp_free_i32(val);
>>> }
>>>
>>> But i do not know how to save the physical, as the physical address is
>>> never passed out of tcg_gen_qemu_st32. what would be the best way to
>>> get the physical address here ? i want to pass it out by the "TCGv
>>> addr here" but it did not work ...
>>
>> This is quite difficult because our fast-path code doesn't actually
>> deal with the guest physical address at all: we create a TLB which
>> maps directly from guest virtual address to host virtual address
>> and use that most of the time.
>>
>> In general you are running into the problem that QEMU is designed
>> to run code fast, not to be easy to instrument.
>
> 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 ?
>
> Xin
>
>>
>> -- PMM
>