Re: [Qemu-devel] Unmaintained QEMU builds

[Peter Maydell]

On 5 September 2010 17:05, Avi Kivity <address@hidden> wrote:
> I'm perfectly fine with dropping it.  btw, there are other features in qemu
> that seem to be academic exercises - *-user for example.  What is it useful
> for?  Most open source stuff is multiplatform, and serious commercial work
> needs something faster than tcg.
>
> I can understand cross-cpu system mode being very useful to embedded or
> kernel developers.  x-on-x is only useful with virtualization, otherwise the
> performance penalty is too great.

Cross-cpu -user mode gets used in embedded development environments
like Scratchbox as a compilation environment, where it gets you a number
of advantages over -system mode:
 * much closer integration with the host filesystem etc
 * you can use a chroot with a mix of native and target-architecture binaries
(so eg bash is the fast native version, gcc is actually a cross compiler,
but target binaries built and run by autoconf also work, via binfmt_misc)
 * it's faster than full system emulation
 * you get to use all your host system's resources rather than just
   (for example) the 256MB RAM the target system supports

(There are disadvantages to doing it that way too, but I think it's a
real, common qemu use case.)

-- Peter Maydell