Re: [Qemu-devel] [PATCH 0/2] introduce "accel=best"

[Andrew Jones]

On Tue, Oct 04, 2016 at 01:07:28PM +0100, Daniel P. Berrange wrote:
> On Tue, Oct 04, 2016 at 02:00:46PM +0200, Andrew Jones wrote:
> > On Tue, Oct 04, 2016 at 01:30:46PM +0200, Laurent Vivier wrote:
> > > This series introduces a new parameter to "accel" to
> > > ask to use the best one.
> > > 
> > > This allows to remove ugly "kvm accelerator not found"
> > > from the "make check" logs.
> > > 
> > > Laurent Vivier (2):
> > >   accel: allows to select the "best" accelerator
> > >   tests: use accel=best instead of accel=kvm:tcg
> > > 
> > >  accel.c                  | 58 
> > > ++++++++++++++++++++++++++++++++++++++++--------
> > >  include/sysemu/accel.h   |  1 +
> > >  kvm-all.c                |  1 +
> > >  qemu-options.hx          |  4 +++-
> > >  qtest.c                  |  1 +
> > >  tests/bios-tables-test.c |  2 +-
> > >  tests/postcopy-test.c    |  8 +++----
> > >  xen-common.c             |  1 +
> > >  8 files changed, 61 insertions(+), 15 deletions(-)
> > 
> > How about probing the host for KVM in the tests. When it's
> > available, then only emit accel=kvm. When it's not (and
> > it's OK to fallback to tcg), then emit only accel=tcg.
> > That's what we do in kvm-unit-tests.
> 
> Arguably unit tests should not have any dependancy on the host hardware,
> and should be using accel=tcg exclusively, so that they have stable and
> predictable behaviour for all developers. Only functional / integration
> tests should have dependancies on host hardware/OS, so where accel=kvm
> would be appropriate.
>

Agreed. However, if you want to make the test case usable for
both TCG and KVM, then it doesn't hurt to give the option.
kvm-unit-tests has an ACCEL env. When it's not set then the
probe, fallback algorithm described above is used. When it is
set (to either kvm or tcg), then it uses only that selection
or fails.

How about doing that here, but with an unset ACCEL having the
default value of tcg?

Thanks,
drew