linux-kernel - Re: [PATCH v7 0/5] Add Intel IOMMU debugfs support

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Date:   Thu, 29 Mar 2018 09:05:35 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Gary R Hook <gary.hook@....com>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH v7 0/5] Add Intel IOMMU debugfs support

On Thu, 29 Mar 2018 10:48:24 +0200
Joerg Roedel <joro@...tes.org> wrote:

> [ Adding Gary from AMD to Cc ]
> 
> On Mon, Mar 19, 2018 at 09:37:14AM -0700, Jacob Pan wrote:
> > On Thu, 15 Mar 2018 14:18:54 +0100
> > Joerg Roedel <joro@...tes.org> wrote:
> >   
> > > On Thu, Feb 15, 2018 at 08:38:11AM -0800, Jacob Pan wrote:  
> > > > Just wondering if your concern is on the implementation or the
> > > > debugfs idea in general. Perhaps have some common IOMMU
> > > > debugfs?    
> > > 
> > > My concern mainly is that we add interfaces which reveal
> > > potentially security relevant information  
> > I don;t think security is any worse than existing kernel page table
> > in debugfs. i.e. /sys/kernel/debug/page_tables
> > This is a debug feature.  
> 
> Okay, so here is the way to go: Please introduce a basic debugfs
> facility to the core iommu code. It should basically only create a
> 'iommu/' directory in debugfs where drivers can create their own
> sub-directories. This must be enabled by a new kconfig option
> (CONFIG_IOMMU_DEBUGFS) and the kernel should print a big fat warning
> at boot when it is enabled. This hopefully prevents anyone from
> enabling it for production kernels.
> 
> Then in the next cycle I will review again more closely what
> information about VT-d and AMD-Vi is revealed there and will probably
> apply what I can live with.
> 
sounds great. we will provide vt-d info for both current and
potential extensions so that you can consider if there can be any
abstractions.

> Thanks,
> 
> 	Joerg
> 

[Jacob Pan]