linux-kernel - Re: [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <alpine.DEB.2.21.1802210934060.24268@nanos.tec.linutronix.de>
Date:   Wed, 21 Feb 2018 09:34:57 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mike Kravetz <mike.kravetz@...cle.com>
cc:     Reinette Chatre <reinette.chatre@...el.com>, fenghua.yu@...el.com,
        tony.luck@...el.com, gavin.hindman@...el.com,
        vikas.shivappa@...ux.intel.com, dave.hansen@...el.com,
        mingo@...hat.com, hpa@...or.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2 13/22] x86/intel_rdt: Support schemata write -
 pseudo-locking core

On Tue, 20 Feb 2018, Mike Kravetz wrote:
> On 02/20/2018 03:21 PM, Thomas Gleixner wrote:
> > The other problem is that we'd need to have MAP_CONTIG first so you
> > actually can allocate physically contigous memory from user space. Mike is
> > working on that, but it's not available today. The only way to do so today
> > (with lots of waste) would be MAP_HUGETLB, which might be an acceptable
> > constraint up to the point where MAP_CONTIG is available.
> 
> Just to clarify, there is not any activity on exposing a general purpose
> MAP_CONTIG interface to user space.  When initially proposed, MAP_CONTIG
> was shot down and the suggestion was to create a new in kernel interface
> to make allocation of contiguous pages easier.  The initial use case was
> a driver which could use the new internal interface as part of it's
> mmap() routine to give contiguous regions to user space.

Thanks for the clarification.

> Reinette is using this new interface, but that must be for the ?immediate
> allocation? case you are trying to move away from.  Sorry, I have not been
> following development of this feature.
> 
> If you would have to create a device to accept a user buffer, could you
> perhaps use the same device to create/hand out a contiguous mapping?

Yes, that's straight forward.

Thanks,

	tglx