linux-kernel - Re: [PATCH 1/3] x86/intel_rdt: Fix issue when mkdir uses a freed CLOSid

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Date:   Wed, 5 Apr 2017 13:17:02 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        vikas.shivappa@...el.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        fenghua.yu@...el.com, h.peter.anvin@...el.com
Subject: Re: [PATCH 1/3] x86/intel_rdt: Fix issue when mkdir uses a freed
 CLOSid

On Wed, Apr 05, 2017 at 11:07:37AM -0700, Luck, Tony wrote:
> On Wed, Apr 05, 2017 at 05:20:24PM +0200, Thomas Gleixner wrote:
> > That's just wrong.
> > 
> > The proper behaviour for a new control group is, that at the time when it
> > is created it copies the CBM values of the default group and not claiming
> > access to ALL of the cache by default.
> 
> I don't see that as any more helpful. When you make a new
> control group it is because none of the existing groups
> provides the QoS that you want.  So the first thing the
> user will do is write the schemata file with the values
> they do want.
> 
> So "all access", or "same as default group" are both the
> same to the user ... not what they want.
> 
> We do need to make sure that the schemata matches what is
> in the registers. We need to make sure that changes to the
> schemata file result in the MSRs being written where needed.

FYI. This behavior and a fix patch were discussed before:
http://lkml.org/lkml/2017/1/9/747

Thanks.

-Fenghua