Re: [Qemu-devel] of apci_1_compatible in CPUHotplugFeatures

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 25 Jan 2019 14:49:28 -0500
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Fri, Jan 25, 2019 at 09:26:05AM +0100, Igor Mammedov wrote:
> > On Wed, 23 Jan 2019 18:28:59 +0000
> > "Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> >   
> > > * Michael S. Tsirkin (mst@redhat.com) wrote:  
> > > > On Tue, Jan 22, 2019 at 08:07:41PM +0000, Dr. David Alan Gilbert wrote:    
> > > > > Hi,
> > > > >   I noticed that the acpi_1_compatible flag was misspelt as
> > > > >                      apci_1_compatible
> > > > > 
> > > > > so have a trivial patch to fix that,  
> > pls post it.
> >   
> > > > > but looking at it - are
> > > > > thre any cases where a[cp]i_1_compatible can possibly be false?  
> > ATM it's not possible, but I've wrote it with intent to reuse
> > build_cpus_aml() in arm/virt board and there we shall use newer
> > aml_device() instead of legacy aml_processor(), hence a feature flag
> > to toggle behavior.  
> 
> Are there imminent plans to do this? If not why don't we
> drop unused code? One can always bring it back from git
> history if need arises but for now there's no guarantee
> it's not broken as it never runs.
I'm working on it (I mean adding CPU hotplug support for ARM (QEMU side of it)),
so I'd keep it.


> >   
> > > > > 
> > > > > Dave    
> > > > 
> > > > legacy_cpu_hotplug so machine 2.6 and older - no?    
> > > 
> > > That doesn't seem to affect that flag by my reading;
> > > the only place I see legacy_cpu_hotplug checked is
> > > acpi-build.c:build_dsdt and we have:
> > > 
> > >     if (pcmc->legacy_cpu_hotplug) {
> > >         build_legacy_cpu_hotplug_aml(dsdt, machine, pm->cpu_hp_io_base);
> > >     } else {
> > >         CPUHotplugFeatures opts = {
> > >             .acpi_1_compatible = true, .has_legacy_cphp = true
> > >         };
> > >         build_cpus_aml(dsdt, machine, opts, pm->cpu_hp_io_base,
> > >                        "\\_SB.PCI0", "\\_GPE._E02");
> > >     }
> > > 
> > > so the 'opts' field is only used in the non-legacy case.
> > > 
> > > That's the only caller of build_cpus_aml, and I'm not seeing another
> > > user of CPUHotplugFeatures.
> > > 
> > > Dave
> > >   
> > > > > --
> > > > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK    
> > > --
> > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK