Re: [Xen-devel] [PATCH] x86/apic: remove the legacy bigsmp APIC driver

[Matt Wilson <msw@xxxxxxxxxx>]

On Tue, Aug 27, 2013 at 09:17:37AM +0100, Jan Beulich wrote:
> >>> On 27.08.13 at 07:44, Matt Wilson <msw@xxxxxxxxxx> wrote:
> > The bigsmp APIC driver was used on legacy (32-bit only) x86 platforms
> > with 8 or more CPUs. In Linux the X86_BIGSMP Kconfig option depends on
> > X86_32. Since we no longer support 32-bit hypervisors on the x86
> > platform we can remove this code.
> 
> The fact that this is 32-bit only in Linux doesn't mean anything.
> Linux has other 64-bit only models, which we don't have (in
> favor of, originally, having a single shared implementation).
> 
> On a system without x2APIC but more than 8 CPUs - how would
> you see us bringing up the CPUs beyond 8? This is particularly
> shown by your adjustment to MP_processor_info_x(), which is
> code removal without replacement.

Aargh, my mistake. I didn't realize that the default driver didn't
have physical flat support, and missed that bigsmp is actually the
physflat implementation.

> Despite Keir's ack, unless I'm overlooking something I'm explicitly
> nack-ing this.

Agreed, sorry for the noise. What we can remove, however, is the DMI
check for 32-bit only systems in the bigsmp code.

It's a bit confusing to call this mode "bigsmp" instead of "physical."
Any thoughts on that?

--msw


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