Re: [PATCH 3/3] hw/arm/virt: Support host CPU type only when KVM or HVF is configured

[Gavin Shan]

Hi Connie,

On 7/13/23 22:46, Cornelia Huck wrote:
> On Thu, Jul 13 2023, Gavin Shan <gshan@redhat.com> wrote:
>
> > The CPU type 'host-arm-cpu' class won't be registered until KVM or
> > HVF is configured in target/arm/cpu64.c. Support the corresponding
> > CPU type only when KVM or HVF is configured.
> >
> > Signed-off-by: Gavin Shan <gshan@redhat.com>
> > ---
> >   hw/arm/virt.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> > index 43d7772ffd..ad28634445 100644
> > --- a/hw/arm/virt.c
> > +++ b/hw/arm/virt.c
> > @@ -217,7 +217,9 @@ static const char *valid_cpu_types[] = {
> >   #endif
> >       ARM_CPU_TYPE_NAME("cortex-a53"),
> >       ARM_CPU_TYPE_NAME("cortex-a57"),
> > +#if defined(CONFIG_KVM) || defined(CONFIG_HVF)
> >       ARM_CPU_TYPE_NAME("host"),
> > +#endif
> >       ARM_CPU_TYPE_NAME("max"),
> >       NULL
> >   };
>
> Doesn't the check in parse_cpu_option() already catch the case where
> the "host" cpu model isn't registered? I might be getting lost in the
> code flow, though.

Right, it's guranteed that the needed CPU type (class) is registered by 
parse_cpu_option().
However, we have different story here. The CPU type invalidation intends to 
limit the CPU type
(class) into a range for the specific machine (board). Taking 
"cortex-a8-arm-cpu" as an example,
it's not expected by hw/arm/virt machines even it has been registered when we 
have CONFIG_TCG=y.
the list of supported CPU type (class) will be dumped by 
hw/core/machine.c::validate_cpu_type()
in PATCH[1], "host" is obviously invalid when we have CONFIG_KVM=n and 
CONFIG_HVF=n. We can't
tell user that "host" is supported, to confuse user.

Thanks,
Gavin