Re: [PATCH kvm-unit-tests] arm64: TCG: Use max cpu type

[Cornelia Huck <cohuck@redhat.com>]

On Fri, Jun 03 2022, Andrew Jones <drjones@redhat.com> wrote:

> On Fri, Jun 03, 2022 at 02:21:10PM +0200, Cornelia Huck wrote:
>> On Fri, Jun 03 2022, Andrew Jones <drjones@redhat.com> wrote:
>> 
>> > The max cpu type is a better default cpu type for running tests
>> > with TCG as it provides the maximum possible feature set. Also,
>> > the max cpu type was introduced in QEMU v2.12, so we should be
>> > safe to switch to it at this point.
>> >
>> > There's also a 32-bit arm max cpu type, but we leave the default
>> > as cortex-a15, because compilation requires we specify for which
>> > processor we want to compile and there's no such thing as a 'max'.
>> >
>> > Signed-off-by: Andrew Jones <drjones@redhat.com>
>> > ---
>> >  configure | 2 +-
>> >  1 file changed, 1 insertion(+), 1 deletion(-)
>> >
>> > diff --git a/configure b/configure
>> > index 5b7daac3c6e8..1474dde2c70d 100755
>> > --- a/configure
>> > +++ b/configure
>> > @@ -223,7 +223,7 @@ fi
>> >  [ -z "$processor" ] && processor="$arch"
>> >  
>> >  if [ "$processor" = "arm64" ]; then
>> > -    processor="cortex-a57"
>> > +    processor="max"
>> >  elif [ "$processor" = "arm" ]; then
>> >      processor="cortex-a15"
>> >  fi
>> 
>> This looks correct, but the "processor" usage is confusing, as it seems
>> to cover two different things:
>> 
>> - what processor to compile for; this is what configure help claims
>>   "processor" is used for, but it only seems to have that effect on
>>   32-bit arm
>> - which cpu model to use for tcg on 32-bit and 64-bit arm (other archs
>>   don't seem to care)
>> 
>> So, I wonder whether it would be less confusing to drop setting
>> "processor" for arm64, and set the cpu models for tcg in arm/run (if
>> none have been specified)?
>>
>
> Good observation, Conny. So, I should probably leave configure alone,
> cortex-a57 is a reasonable processor to compile for, max is based off
> that.

Yes, it would be reasonable; however, I only see Makefile.arm put it
into CFLAGS, not Makefile.arm64, unless I'm missing something here. But
it doesn't hurt, either.

> Then, I can select max in arm/run for both arm and arm64 tests
> instead of using processor there.

Unless you want to be able to override this via -processor=
explicitly... although I doubt that this is in common use.