[Qemu-devel] Re: [questions] savevm|loadvm

[Wenhao Xu]

Hi, Juan,
   I am fresh to both QEMU and KVM. But so far, I notice that QEMU
uses "KVM_SET_USER_MEMORY_REGION" to set memory region that KVM can
use and uses cpu_register_physical_memory_offset to register the same
memory to QEMU emulator, which means QEMU and KVM use the same host
virtual memory. And therefore the memory KVM modified could be
directly reflected to QEMU. I don't quite understand the different
memory layout problem between the two. So I don't know exactly what
you mean to "fix" it?

   For why switching is useful? Actually, I am a master student now
and doing a course project. What am I arguing is that QEMU could be
potentially useful to do many instrumentation analysis, but it is a
bit slow. So by combing with KVM, when the os runs to some place where
we are interested in, switch it to QEMU emulator mode and do the
analysis and then switch back.
   FYI, there is a paper doing so in Xen, "Practical taint-based
protection using demand emulation". I want to do the same "demand
emulation" for KVM.

   I am trying to patch some code.  When kvm_run returns, I tried to
synchronize the CPU state and memory dirty map, and then run into QEMU
emulator mode. However, I got an error, "qemu: fatal: invalid tss
type". I don't know exactly where is the problem.

   Thanks for helping me working this out. I am really stuck into this problem.

regards,
Wenhao

On Tue, Mar 30, 2010 at 1:22 AM, Juan Quintela <address@hidden> wrote:
> Wenhao Xu <address@hidden> wrote:
>> Hi, all,
>> żď˝ I am working with switching QEMU from running in KVM mode to QEMU
>> emulatoin mode dynamically.
>> żď˝ Intuitively, if the snapshot created using savevm in kvm mode can be
>> used by the loadvm command in QEMU emulator mode, the switchment could
>> makes use of this.ż I tried to do so. However, it does not work.ż Any idea
>> how to fix it?
>> żď˝ż Thanks for the help.
>
> kvm uses a different memory layout (slots in qemu/kvm lingo), that means
> that memory can't be migrated (that is a big problem).  Once that is
> "fixed", you need to work on the several in-kernel chips that don't
> exist in qemu (kvm-irq-chip and the like).  Once that is fixed, you can
> look for what more things are broken.
>
> Once here, why do you want to do that switch?
>
> Later, Juan.
>
>> regards,
>> Wenhao
>>
>> --
>> ~_~
>



-- 
~_~