linux-kernel - Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event

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Date:   Tue, 27 Sep 2016 15:49:57 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after
 soft remove event

On Tue, Sep 27, 2016 at 07:45:56AM -0400, Prarit Bhargava wrote:
> On 09/26/2016 07:57 AM, Borislav Petkov wrote:
> > $ echo 0 > /sys/devices/system/cpu/cpu2/online
> 
> This results in the topology directory being destroyed.  It shouldn't be -- the
> socket and core are still there.  If you could open up your computer you could
> touch them.  This is similar to downing a PCI device, or removing !kernel memory
> DIMM from a system.  The device is still physically there.

If you remove a PCI device from the system, by turning it off from the
PCI hotplug interface, it will go away from sysfs, just like this CPU
device is going away, no matter if you physically remove the device or
not.

Thanks for validating that everything is working the same and correctly
:)

greg k-h