Re[2]: [Qemu-devel] qemu dynamic translation (system design) question

[Paul Sokolovsky]

Hello S.P.T.Krishnan,

Sunday, August 20, 2006, 6:23:11 PM, you wrote:

> Hi Laurent,

> Thanks for the direction.

> I am just thinking.  If I run a guest OS once and observe the blocks
> that are translated and may be reused.  Then I again re-run the OS,
> can I expect the same blocks are translated ?  i.e., is qemu
> consistent on how it partitions the asm into blocks on successive runs
> or the guest OS ?

> Note: in both cases the user doesn't interact with the Guest OS.  It
> is up for, say 1 min and then shutdown in both runs.

  My 2 cents of pure scholastic reasoning:
  
  Let's assume that QEMU uses deterministic rules for block
translation. Then, it just translates what CPU goes thru. Does any
contemporary OS leads CPU in deterministic ways? No. It largely
depends on various environment parameters, of which user interaction
is not the last. There're interrupts occuring in rather random places
with respect to mainline execution, I/O delays, etc. As these
parameters in guest OS depend on QEMU's interaction with host OS, they
are not deterministic in it either. Well, but does QEMU's translation
itself deterministic? Not really, as it uses caches, and thus depend on
memory parameters in host OS.

> regards,
> Krishnan


-- 
Best regards,
 Paul                            mailto:address@hidden