Re: [PATCH 34/35] x86: use num_processors for possible cpus

From: H. Peter Anvin
Date: Wed Feb 17 2010 - 20:33:44 EST


On 02/10/2010 01:20 AM, Yinghai Lu wrote:
> some systems that have disable cpus entries because same
> BIOS will support 2 sockets and 4 sockets and more at
> same time, BIOS just leave some disable entries, but
> those system do not support cpu hotplug. we don't need
> treat disabled_cpus as hotplug cpus.
> so we can make nr_cpu_ids smaller and save more space
> (pcpu data allocations), and could make some systems run
> with logical flat instead of physical flat apic mode
>
> -v2: change to black list instead
> -v3: just remove that, and the one use possible_cpus= directly.
>
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

I'm confused by this one. This would seem to mean that unless you're
specifying possible_cpus= then you are not treating anything as
hotpluggable.

This is clearly wrong, and it would appear to go the wrong direction in
terms of what is safe.

What am I missing here?

-hpa
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