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From: Shivappa Vikas <vikas.shivappa@intel.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Vikas Shivappa <vikas.shivappa@linux.intel.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org, hpa@zytor.com,
	peterz@infradead.org, ravi.v.shankar@intel.com,
	vikas.shivappa@intel.com, tony.luck@intel.com,
	fenghua.yu@intel.com, andi.kleen@intel.com
Subject: Re: [PATCH 21/21] x86/intel_rdt/mbm: Handle counter overflow
Date: Thu, 6 Jul 2017 16:53:40 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.10.1707061651540.3798@vshiva-Udesk> (raw)
In-Reply-To: <alpine.DEB.2.20.1707021548460.2296@nanos>



On Sun, 2 Jul 2017, Thomas Gleixner wrote:

> On Mon, 26 Jun 2017, Vikas Shivappa wrote:
>> +static void mbm_update(struct rdt_domain *d, int rmid)
>> +{
>> +	struct rmid_read rr;
>> +
>> +	rr.first = false;
>> +	rr.d = d;
>> +
>> +	if (is_mbm_total_enabled()) {
>> +		rr.evtid = QOS_L3_MBM_TOTAL_EVENT_ID;
>> +		__mon_event_count(rmid, &rr);
>
> This is broken as it is not protected against a concurrent read from user
> space which comes in via a smp function call.

The read from user also has the rdtgroup_mutex.

Thanks,
Vikas

>
> This means both the internal state and __rmid_read() are unprotected.
>
> I'm not sure whether it's enough to disable interrupts around
> __mon_event_count(), but that's the minimal protection required. It's
> definitely good enough for __rmid_read(), but it might not be sufficient
> for protecting domain->mbm_[local|total]. I leave the exercise of figuring
> that out to you.
>
> Thanks,
>
> 	tglx
>

  reply	other threads:[~2017-07-06 23:52 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-26 18:55 [PATCH V1 00/21] x86/cqm3: Resctrl based cqm Vikas Shivappa
2017-06-26 18:55 ` [PATCH 01/21] x86/perf/cqm: Wipe out perf " Vikas Shivappa
2017-06-26 18:55 ` [PATCH 02/21] x86/intel_rdt: Fix memory leak during mount Vikas Shivappa
2017-06-30 19:24   ` [tip:x86/urgent] x86/intel_rdt: Fix memory leak on mount failure tip-bot for Vikas Shivappa
2017-06-26 18:55 ` [PATCH 03/21] x86/intel_rdt/cqm: Documentation for resctrl based RDT Monitoring Vikas Shivappa
2017-06-26 18:55 ` [PATCH 04/21] x86/intel_rdt: Introduce a common compile option for RDT Vikas Shivappa
2017-06-26 18:55 ` [PATCH 05/21] x86/intel_rdt: Change file names to accommodate RDT monitor code Vikas Shivappa
2017-06-26 18:55 ` [PATCH 06/21] x86/intel_rdt: Cleanup namespace to support RDT monitoring Vikas Shivappa
2017-06-26 18:55 ` [PATCH 07/21] x86/intel_rdt/cqm: Add RDT monitoring initialization Vikas Shivappa
2017-07-02  9:14   ` Thomas Gleixner
2017-07-06 21:07     ` Shivappa Vikas
2017-06-26 18:55 ` [PATCH 08/21] x86/intel_rdt/cqm: Add RMID(Resource monitoring ID) management Vikas Shivappa
2017-07-02 10:05   ` Thomas Gleixner
2017-07-03  9:55     ` Thomas Gleixner
2017-07-05 15:34       ` Peter Zijlstra
2017-07-05 17:25         ` Thomas Gleixner
2017-07-11 23:54       ` Shivappa Vikas
2017-07-12 20:14         ` Thomas Gleixner
2017-07-05 17:59     ` Tony Luck
2017-07-06  6:51       ` Thomas Gleixner
2017-06-26 18:55 ` [PATCH 09/21] x86/intel_rdt: Simplify info and base file lists Vikas Shivappa
2017-07-02 10:09   ` Thomas Gleixner
2017-07-06 21:09     ` Shivappa Vikas
2017-06-26 18:55 ` [PATCH 10/21] x86/intel_rdt/cqm: Add info files for RDT monitoring Vikas Shivappa
2017-06-26 18:55 ` [PATCH 11/21] x86/intel_rdt/cqm: Add mkdir support " Vikas Shivappa
2017-07-02 10:58   ` Thomas Gleixner
2017-07-06 21:23     ` Shivappa Vikas
2017-06-26 18:55 ` [PATCH 12/21] x86/intel_rdt/cqm: Add tasks file support Vikas Shivappa
2017-07-02 11:01   ` Thomas Gleixner
2017-07-06 21:25     ` Shivappa Vikas
2017-06-26 18:56 ` [PATCH 13/21] x86/intel_rdt/cqm: Add cpus " Vikas Shivappa
2017-07-02 11:11   ` Thomas Gleixner
2017-07-06 21:26     ` Shivappa Vikas
2017-07-02 12:29   ` Thomas Gleixner
2017-07-06 21:42     ` Shivappa Vikas
2017-07-07  6:44       ` Thomas Gleixner
2017-07-13 18:37         ` Shivappa Vikas
2017-07-13 22:09     ` Shivappa Vikas
2017-06-26 18:56 ` [PATCH 14/21] x86/intel_rdt/cqm: Add mon_data Vikas Shivappa
2017-07-02 12:43   ` Thomas Gleixner
2017-07-06 21:48     ` Shivappa Vikas
2017-07-07  6:22       ` Thomas Gleixner
2017-07-11 21:17         ` Shivappa Vikas
2017-07-11 21:37           ` Luck, Tony
2017-06-26 18:56 ` [PATCH 15/21] x86/intel_rdt/cqm: Add rmdir support Vikas Shivappa
2017-07-02 13:16   ` Thomas Gleixner
2017-07-06 21:49     ` Shivappa Vikas
2017-06-26 18:56 ` [PATCH 16/21] x86/intel_rdt/cqm: Add mount,umount support Vikas Shivappa
2017-07-02 13:22   ` Thomas Gleixner
2017-07-06 21:58     ` Shivappa Vikas
2017-06-26 18:56 ` [PATCH 17/21] x86/intel_rdt/cqm: Add sched_in support Vikas Shivappa
2017-07-02 13:37   ` Thomas Gleixner
2017-07-06 23:35     ` Shivappa Vikas
2017-06-26 18:56 ` [PATCH 18/21] x86/intel_rdt/cqm: Add hotcpu support Vikas Shivappa
2017-06-26 18:56 ` [PATCH 19/21] x86/intel_rdt/mbm: Basic counting of MBM events (total and local) Vikas Shivappa
2017-07-02 13:46   ` Thomas Gleixner
2017-07-06 23:39     ` Shivappa Vikas
2017-07-07  6:47       ` Thomas Gleixner
2017-06-26 18:56 ` [PATCH 20/21] x86/intel_rdt/mbm: Add mbm counter initialization Vikas Shivappa
2017-06-26 18:56 ` [PATCH 21/21] x86/intel_rdt/mbm: Handle counter overflow Vikas Shivappa
2017-07-02 13:57   ` Thomas Gleixner
2017-07-06 23:53     ` Shivappa Vikas [this message]
2017-07-07  6:50       ` Thomas Gleixner
2017-07-10 17:54         ` Luck, Tony
2017-07-11 15:22           ` Thomas Gleixner

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