Re: [gentoo-user] mostly OT: qemu sparc64 emulation

[Walter Dnes]

On Mon, Oct 30, 2017 at 08:43:50AM -0700, Ian Zimmerman wrote
> I built the gentoo qemu package [1] with support for a couple of
> non-x86 arches.  Trying the sparc64 one, I installed FreeBSD-11.1
> into it.  It kind of works, but:
>
> 1.  It's very slow - I estimate about 5x-10x slower than an emulated
> x86_64, also running FreeBSD-11.1.

  Think this through; when running an x86_64 VM on an x86_64 host,
you're usually doing *HARDWARE* "emulation"; i.e. the compiled code
machine language instructions are handled native by the physical cpu if
you lanch with "qemu-system-x86_64 -enable-kvm".  Try software-only
emulation by launching with "qemu-x86_64" instead.  Guess what... it's
also very slow.  Since x86_64 does not have native sparc instructions,
it *MUST* use software emulation; hence the slow speed.

> 2.  1 processor on the host (a 4-way Phenom) is always at 100%, even
> when the guest is completely idle.  This makes me think there is a
> virtual interrupt line that is always on, and this probably is the
> cause of #1.  Again, this doesn't happen when the guest CPU is x86_64.
>
> 3.  There is no emulated network device.  This could be related to the
> ne2k_pci issue mentioned at [2].  I'd be willing to debug this, _if_ it
> were not for #1 and #2 ...
>
> anyone has a guess what is happening here?

  I run an OS/2 VM with a bunch of parameters that may not apply to your
case.  Are any of them relavant to you, e.g. "-parallel none"?

#!/bin/bash
cd /home/misc/qemu/os2
sudo /usr/bin/qemu-system-x86_64 -enable-kvm -runas waltdnes \
   -cpu pentium3 -monitor vc \
   -drive file=os2c.img,format=raw \
   -drive file=os2d.img,format=raw \
   -netdev user,id=mynetwork,tftp=/dev/shm/xfer \
   -device pcnet,netdev=mynetwork \
   -rtc base=localtime,clock=host \
   -m size=64 -name "OS/2 VM" -boot order=c \
   -vga std -parallel none \
   ${@}

-- 
Walter Dnes <waltdnes@××××××××.org>
I don't run "desktop environments"; I run useful applications