Re: [Xen-devel] [PATCH 1/6] x86: detect and initialize Intel CAT feature

[Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>]

On Fri, Mar 13, 2015 at 09:40:13AM -0400, Konrad Rzeszutek Wilk wrote:
> On Fri, Mar 13, 2015 at 06:13:20PM +0800, Chao Peng wrote:
> > Detect Intel Cache Allocation Technology(CAT) feature and store the
> > cpuid information for later use. Currently only L3 cache allocation is
> > supported. The L3 CAT features may vary among sockets so per-socket
> > feature information is stored. The initialization can happen either at
> > boot time or when CPU(s) is hot plugged after booting.
> > 
> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> > ---
> >  docs/misc/xen-command-line.markdown |  15 +++-
> >  xen/arch/x86/psr.c                  | 151 
> > +++++++++++++++++++++++++++++++++---
> >  xen/include/asm-x86/cpufeature.h    |   1 +
> >  3 files changed, 155 insertions(+), 12 deletions(-)
> > 
> > +    cat_cpu_init(smp_processor_id());
> 
> Do 'if (!cat_cpu_init(..)).`'
> 
> as the CPU might not support this.
> 
> At which point you should also free the cat_socket_info and
> not register the cpu notifier.

Even the booting CPU does not support this, other CPUs may still support
this. Generally the feature is a per-socket feature. So break here is
not the intention.

Except this, all other comments will be addressed by the next version.
Thanks for your time.

Chao
> 
> > +    register_cpu_notifier(&cpu_nfb);
> > +}
> > +

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