Re: [RFC 8/8] x86_64: Support for new UV apic

From: Jack Steiner
Date: Sun Mar 30 2008 - 17:04:19 EST


On Sun, Mar 30, 2008 at 01:23:12PM -0700, Yinghai Lu wrote:
> On Wed, Mar 26, 2008 at 12:38 AM, Ingo Molnar <mingo@xxxxxxx> wrote:
> >
> > * Jack Steiner <steiner@xxxxxxx> wrote:
> >
> > > > > - obj-y += genapic_64.o genapic_flat_64.o
> > > > > + obj-y += genapic_64.o genapic_flat_64.o genx2apic_uv_x.o
> > > >
> > > > Definitely should be a CONFIG
> > >
> > > Not sure that I understand why. The overhead of UV is minimal & we
> > > want UV enabled in all distro kernels. OTOH, small embedded systems
> > > probably want to eliminate every last bit of unneeded code.
> > >
> > > Might make sense to have a config option. Thoughts????
> >
> > i wouldnt mind having UV enabled by default (it can be a config option
> > but default-enabled on generic kernels so all distros will pick this hw
> > support up), but we definitely need the genapic unification before we
> > can add more features.
>
> config option would be reasonable.
> for x86_64
> subarch already have X86_PC, X86_VSMP.
> we have X86_UVSMP

If there was a significant differece between UV and generic kernels
(or hardware), then I would agree. However, the only significant
difference is the APIC model on large systems. Small systems are
exactly compatible.

The problem with subarch is that we want 1 binary kernel to support
both generic hardware AND uv hardware. This restriction is desirable
for the distros and software vendors. Otherwise, additional kernel
images would have to be built, released, & certified.

--- jack

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