lkml.org 
[lkml]   [2009]   [Jan]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] x86: put trigger in to detect mismatched apic versions.

* Jack Steiner <steiner@sgi.com> wrote:

> > Btw, I checked with our UV architect and the problem is that we need a
> > 16 bit apic id which is what caused the MAX_APICS to be bumped to 32k.
> > The lower 8 bits are the normal apic id, and the upper bit relate to
> > the node. This means cpu 0 on node 0 has the same apic id as cpu 0 on
> > node 1, etc. I also asked about whether we could rely on always
> > having
>
> Not strictly true. The apicids in the ACPI tables are always globally
> unique across the entire system. Because of the size of UV systems, UV
> needs 16 bit apicids. This fits in the ACPI apicid id/eid fields.
>
> The actual processor apicid register is unfortunately only 11 bits and
> there are some restrictions on the actual values loaded into the apicid
> register.
>
> If we can put unique ids into the apicid register, we do. If we can't,
> the function that reads the apicid will automatically supply the rest of
> the bits. Most of the kernel is unaware that the processor apicid
> register may have only a subset of the bits that are in the ACPI tables.

apicid remapping is something we need/want, so we cannot remove that
array. But it would be nice to offload such properties to the percpu area
instead - is there any reason why that is hard? The local apic is attached
to a CPU in any case. Is there some early init reason that complicates
this?

Ingo


\
 
 \ /
  Last update: 2009-01-18 20:11    [W:0.916 / U:0.404 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site