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

[Wei-Ren Chen]

On Wed, Aug 22, 2012 at 09:38:17PM -0700, Xin Tong wrote:
> On Wed, Aug 22, 2012 at 8:14 PM, 陳韋任 (Wei-Ren Chen)
> <address@hidden> wrote:
> >> In tcg_gen_qemu_ld8s(tmp, addr, index); a TCGv addr is passed to the
> >> INDEX_op_qemu_ld8s as param and the loaded value is passed back in
> >> tmp. i want to get the translated value as well.  how can i do that ?
> >
> >   IIUC, qemu_ld takes addr as guest virtual address, then loads the
> > value in that address into tmp. So, what "translated value" you mean
> > here? The guest physical address, host virtual address, or the value
> > of the guest virtual address?
> 
> either the guest physical or the host virtual is fine with me. but
> better to be guest physical. i think guest physical can be obtained by
> subtracting host virtual with a fixed offset for ram. but the thing i
> do not know how to do is how to pass the guest physical back, can i
> store the guest physical in the TCGv from the guest virtual.

  qemu_ld will go through software tlb first, you will get host virtual
address there. It will go ld{b,w,l,q}_mmu if software tlb miss, call
tlb_fill -> cpu_x86_handle_mmu_fault, you can get guest physical address
there (target_phys_addr_t paddr). If you want to get guest physical
address for each guest memory access, I guess you need to disable
software tlb lookup, you can refer to Max's patch [1]. Or as you said,
maybe you can get guest physical addr from host virtual addr. You can
refer to cpu_physical_memory_map (exec.c) which map guest physical addr
to host virtual addr, then see how you can do the reverse.

HTH,
chenwj

[1] http://lists.gnu.org/archive/html/qemu-devel/2012-08/msg03226.html

-- 
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