Re: [PATCH v4 1/3] target-arm: Add support for Fujitsu A64FX

[Andrew Jones <drjones@redhat.com>]

On Tue, Aug 17, 2021 at 05:53:34AM -1000, Richard Henderson wrote:
> On 8/17/21 5:36 AM, Andrew Jones wrote:
> > On Tue, Aug 17, 2021 at 05:23:17AM -1000, Richard Henderson wrote:
> > > On 8/17/21 1:56 AM, Andrew Jones wrote:
> > > > I guess it's fine. You could easily create a new cpu_arm_set_sve_vq()
> > > > which would forbid changing the properties if you wanted to, but then
> > > > we need to answer Peter's question in order to see if there's a
> > > > precedent for that type of property.
> > > 
> > > I don't see the point in read-only properties.  If the user wants to set
> > > non-standard values on the command-line, let them.  What is most important
> > > is getting the correct default from '-cpu a64fx'.
> > > 
> > 
> > So maybe we should just go ahead and add all sve* properties, but then
> > make sure the default vq map is correct.
> 
> I think that's the right answer.
> 
> Presently we have a kvm_supported variable that's initialized by
> kvm_arm_sve_get_vls().  I think we want to rename that variable and provide
> a version of that function for tcg. Probably we should have done that
> before, with a trivial function for -cpu max to set all bits.
> 
> Then eliminate most of the other kvm_enabled() checks in
> arm_cpu_sve_finalize.  I think the only one we keep is the last, where we
> verify that the final sve_vq_map matches kvm_enabled exactly, modulo max_vq.
> 
> This should minimize the differences in behaviour between tcg and kvm.

That's a good idea. I'll send a patch with your suggested-by.

Thanks,
drew