Re: [Xen-devel] [PATCH v10 02/13] x86: detect and initialize Intel CAT feature

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 26.06.15 at 10:43, <chao.p.peng@xxxxxxxxxxxxxxx> 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>
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> Changes in v0:
> * Add comment for cpu notification priority.

I'm afraid you did this just mechanically, while I implied you to also
verify that what you chose is correct:

>  static struct notifier_block cpu_nfb = {
> -    .notifier_call = cpu_callback
> +    .notifier_call = cpu_callback,
> +    /*
> +     * Ensure socket_cpumask is still valid in CPU_DEAD notification
> +     * (E.g. the CPU_DEAD notification should be called ahead of
> +     * cpu_smpboot_free).
> +     */
> +    .priority = 1

CPU_DEAD is a NOTIFY_REVERSE notification, i.e. lowest priority
first. I.e. your comment now contradicts the code afaict. Unless
I'm mistaken with that, I assume you didn't really test this code
path? Since everything else is fine with this patch, I'd be fine
with doing the adjustment while committing, but I need your
confirmation which variant actually works.

Jan


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