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Re: [Qemu-devel] qemu-kvm command-line compat


From: Michael Tokarev
Subject: Re: [Qemu-devel] qemu-kvm command-line compat
Date: Tue, 22 Jan 2013 09:09:50 +0400
User-agent: Mozilla/5.0 (X11; Linux i686 on x86_64; rv:17.0) Gecko/17.0 Icedove/17.0

18.01.2013 09:28, Michael Tokarev wrote:

As far as I remember, qemu-kvm had quite some differences compared
with qemu, at least:

  -accel kvm,tcg
  -cpu kvm64 (or kvm32?)
  -kernel_irqchip (machine option)

The latter two aren't needed.

I'm not sure when, but apparently qemu-kvm switched to qemu64 CPU
by default a while back, and kvm64 CPU has a few flags less than
qemu64.  So the default is right here, and -cpu kvm64 is actually
making things worse.

For kernel_irqchip, at least in 1.3 it is on by default, so it is
just not needed.

So, what we left with is just one:

  -accel kvm:tcg

which is manageable.

There _was_ one more difference - qemu-kvm had VGA ram size = 16M,
while old qemu had it equal to 8M.  But now qemu switched to 16M
as well, so it should be fine.

So, my question is, -- what to suggest to use when a user switches
from qemu-kvm to qemu now?

I can try to come up with a compat script of some sort which will
try to translate old qemu-kvm command line to new qemu command line,
something like:

  exec qemu-system-x86_64 -machine accel=kvm:tcg,kernel_irqchip=on -cpu kvm64 
"$@"

   exec qemu-system-x86_64 -machine accel=kvm:tcg "$@"

works fine, on x86 anyway.

Thanks,

/mjt



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