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

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Date:   Tue, 13 Feb 2018 15:03:03 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Sohil Mehta <sohil.mehta@...el.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        Ashok Raj <ashok.raj@...el.com>,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        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>
Subject: Re: [PATCH v7 0/5] Add Intel IOMMU debugfs support

On Fri, Feb 02, 2018 at 04:49:56PM -0800, Sohil Mehta wrote:
> This series aims to add debugfs support for Intel IOMMU. It exposes IOMMU
> registers, internal context and dumps individual table entries to help debug
> Intel IOMMUs.
> 
> The first patch does the ground work for the following patches by reorganizing
> some Intel IOMMU data structures. The following patches create a new Kconfig
> option - INTEL_IOMMU_DEBUG and add debugfs support for IOMMU context internals,
> register contents, PASID internals, and Interrupt remapping in that order. The
> information can be accessed in sysfs at '/sys/kernel/debug/intel_iommu/'.

This looks like it only presents data from the iommu-hardware (register
state) or from in-memory data structures used by the hardware. Can't all
this be read out from user-space with libpci and /dev/mem access?

Things are different for kernel-defined data structures, as they might
change between releases and can be presented to user-space via debugfs
is needed, but the data structures used by the hardware should be pretty
stable.


	Joerg