Re: [PATCH] arm/run: don't enable KVM if system can't do it

[Andrew Jones <drjones@redhat.com>]

On Thu, Jul 02, 2015 at 12:05:31PM +0100, Alex Bennée wrote:
> As ARM (and no doubt other systems) can also run tests in pure TCG mode
> we might as well not bother enabling accel=kvm if we aren't on a real
> ARM based system. This prevents us seeing ugly warning messages when
> testing TCG.

First,
YAY! We're getting contributions to kvm-unit-tests/arm!

> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> ---
>  arm/run | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/arm/run b/arm/run
> index 662a856..2bdb4be 100755
> --- a/arm/run
> +++ b/arm/run
> @@ -33,7 +33,13 @@ if $qemu $M -chardev testdev,id=id -initrd . 2>&1 \
>  	exit 2
>  fi
>  
> -M='-machine virt,accel=kvm:tcg'
> +host=`uname -m | sed -e 's/arm.*/arm/'`
> +if [ "${host}" = "arm" ] || [ "${host}" = "aarch64" ]; then
> +    M='-machine virt,accel=kvm:tcg'
> +else
> +    M='-machine virt,accel=tcg'
> +fi

I think this is a good idea, although I had actually left that warning
on purpose. Originally, the plan was for these unit tests to be kvm
specific. If they could be developed with the aid of tcg, and even used
to test tcg, then fine, but running them on tcg should always complain,
in order to make sure that the test output clearly showed that it had
not been running on kvm. Developing unit tests for tcg is also a good
idea though, and there's really no reason not to share this framework.

So, for this patch I'd prefer we do a few things differently;

1) we should be able to integrate this new condition with the
   "arm64 must use '-cpu host' with kvm" condition that is lower down.
   And, let's just make this $HOST variable one that ./configure
   prepares, allowing that arm64 condition to s/$(arch)/$HOST/ and
   avoiding the need to duplicate the sed -e 's/arm.*/arm/'

2) we might as well do something like

   M='-machine virt'
   if using-kvm
     M+=',accel=kvm'
   else
     M+=',accel=tcg'
   fi

   now, since we don't want to use the accel fallback feature anymore

3) outputting which one we're using might still be nice, otherwise
   one must inspect the qemu command line in the logs to find out

4) I recently mentioned[*] it might be nice to add a '-force-tcg' type
   of arm/run command line option, allowing tcg to be used even if
   it's possible to use kvm. Adding that at the same time would be
   nice.

5) we use tabs for indentation in arm/run, and only bother with the
   variable's {}, if necessary

6) we should post patches with [kvm-unit-tests PATCH] to avoid
   confusion with other kvm postings. (I screwed that up on my
   last two postings...).

Thanks!
drew

[*] https://lists.gnu.org/archive/html/qemu-devel/2015-06/msg07514.html

> +
>  chr_testdev='-device virtio-serial-device'
>  chr_testdev+=' -device virtconsole,chardev=ctd -chardev testdev,id=ctd'
>  
> -- 
> 2.4.5
> 
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