Re: [PATCH] x86: add apic probe for genapic 64bit v2
From: Suresh Siddha
Date: Tue Jul 22 2008 - 14:11:14 EST
On Tue, Jul 22, 2008 at 11:05:17AM -0700, Yinghai Lu wrote:
> On Tue, Jul 22, 2008 at 10:57 AM, Suresh Siddha
> <suresh.b.siddha@xxxxxxxxx> wrote:
> > Yinghai, though not directly realted to this probe cleanup, what is this
> > 'max_physical_apicid' doing.
> > I don't understand the need for this commit.
> >> commit e0da33646826b66ef933d47ea2fb7a693fd849bf
> >> Author: Yinghai Lu <yhlu.kernel@xxxxxxxxx>
> >> Date: Sun Jun 8 18:29:22 2008 -0700
> >> x86: introduce max_physical_apicid for bigsmp switching
> >> a multi-socket test-system with 3 or 4 ioapics, when 4 dualcore cpus or
> >> 2 quadcore cpus installed, needs to switch to bigsmp or physflat.
> >> CPU apic id is [4,11] instead of [0,7], and we need to check max apic
> >> id instead of cpu numbers.
> > for logical flat, it really shouldn't matter how large the physical apic id
> > is. In logical flat, OS programs the LDR and the limitation is the
> > number of cpu's which is '8'.
> before i clean up 32bit, 64bit already used max_physical_apicid to
> check if need to switch to physflat.
No. It was introduced by your commit e0da33646826b66ef933d47ea2fb7a693fd849bf
we were using num_possible_cpus > 8 check before.
> for 32bit, if not switch to bigsmp, cpu with physical apic id >=8 can
> not be started by BSP.
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