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From: Thomas Gleixner <>
To: Vikas Shivappa <>
Subject: Re: [PATCH 1/3] x86/intel_rdt: Fix issue when mkdir uses a freed CLOSid
Date: Wed, 5 Apr 2017 17:20:24 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.20.1704051714460.2803@nanos> (raw)
In-Reply-To: <>

On Mon, 3 Apr 2017, Vikas Shivappa wrote:

> Subject: x86/intel_rdt: Fix issue when mkdir uses a freed CLOSid

This subject line is useless again. It want's to be descriptive.

"Fix issue" Which issue?

> Each resctrl directory has one CLOSid allocated which is mapped to a
> control register/QOS_MSR. During an rmdir this CLOSid is freed and can
> be reused later when a new directory is created.  Currently we do not
> reset the QOS_MSR to a default when the CLOSid is freed. So when the
> next mkdir uses a freed CLOSid, the new directory is associated with a
> stale QOS_MSR.

That's not an issue. That's maybe something people are not expecting.

> Fix this issue by writing a default value to the QOS_MSR when the
> associated CLOSid is freed. The default value is all 1s for CBM which
> means no control is enforced when a mkdir reuses this CLOSid.

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.



  reply	other threads:[~2017-04-05 15:20 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-03 21:44 [PATCH 0/3 V3] x86/intel_rdt: Improvements/Fixes to RDT framework Vikas Shivappa
2017-04-03 21:44 ` [PATCH 1/3] x86/intel_rdt: Fix issue when mkdir uses a freed CLOSid Vikas Shivappa
2017-04-05 15:20   ` Thomas Gleixner [this message]
2017-04-05 18:03     ` Shivappa Vikas
2017-04-05 18:07     ` Luck, Tony
2017-04-05 20:17       ` Fenghua Yu
2017-04-10 17:08       ` Thomas Gleixner
2017-04-11 18:51         ` Shivappa Vikas
2017-04-03 21:44 ` [PATCH 2/3] x86/intel_rdt: Implement "update" mode when writing schemata file Vikas Shivappa
2017-04-05 15:27   ` [tip:x86/cpu] " tip-bot for Tony Luck
2017-04-03 21:44 ` [PATCH 3/3] x86/intel_rdt: Update schemata read to show data in tabular format Vikas Shivappa
2017-04-05 15:28   ` [tip:x86/cpu] " tip-bot for Vikas Shivappa

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