linux-kernel - Re: [PATCH v2] iommu/vt-d: Dump DMAR translation structure

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Message-ID: <YP6pw9j8i3bGOb13@8bytes.org>
Date:   Mon, 26 Jul 2021 14:25:39 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     Kyung Min Park <kyung.min.park@...el.com>
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        baolu.lu@...ux.intel.com, dwmw2@...radead.org, will@...nel.org,
        yian.chen@...el.com, sohil.mehta@...el.com,
        ravi.v.shankar@...el.com, ashok.raj@...el.com
Subject: Re: [PATCH v2] iommu/vt-d: Dump DMAR translation structure

On Wed, Jul 21, 2021 at 09:24:53PM -0700, Kyung Min Park wrote:
> When the dmar translation fault happens, the kernel prints a single line
> fault reason with corresponding hexadecimal code defined in the Intel VT-d
> specification.
> 
> Currently, when user wants to debug the translation fault in detail,
> debugfs is used for dumping the dmar_translation_struct, which is not
> available when the kernel failed to boot.
> 
> Dump the DMAR translation structure, pagewalk the IO page table and print
> the page table entry when the fault happens.
> 
> Signed-off-by: Kyung Min Park <kyung.min.park@...el.com>

This is too much noise in dmesg for a single dmar fault. Please hide
that additional debug information behind a debug kernel option for the
VT-d driver.

Thanks,
	
	Joerg