linux-kernel - Re: [iommu/vt] c9ac3b69cf: WARNING:at_drivers/iommu/intel-iommu.c:#dmar_parse_one

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Date:   Mon, 3 Feb 2020 11:02:12 -0500
From:   Barret Rhoden <brho@...gle.com>
To:     kernel test robot <rong.a.chen@...el.com>
Cc:     0day robot <lkp@...el.com>, LKML <linux-kernel@...r.kernel.org>,
        lkp@...ts.01.org
Subject: Re: [iommu/vt] c9ac3b69cf:
 WARNING:at_drivers/iommu/intel-iommu.c:#dmar_parse_one_rmrr

Hi -

On 2/3/20 4:10 AM, kernel test robot wrote:
> FYI, we noticed the following commit (built with gcc-7):
> 
> commit: c9ac3b69cfdbc46a0504fa353b5126827e4b0bdb ("iommu/vt-d: skip RMRR entries that fail the sanity check")
> https://github.com/0day-ci/linux/commits/Barret-Rhoden/iommu-vt-d-bad-RMRR-workarounds/20200109-051817

This looks like your system's firmware might be buggy, which is what the 
warning is all about.

 From the kmesg:

> kern  :info  : [    2.912758] DMAR: RMRR base: 0x0000009f271000 end: 0x0000009f290fff
> kern  :info  : [    2.919226] DMAR: RMRR base: 0x000000a1800000 end: 0x000000a3ffffff
> kern  :err   : [    2.925692] DMAR: [Firmware Bug]: No firmware reserved region can cover this RMRR [0x00000000a1800000-0x00000000a3ffffff], contact BIOS vendor for fixes
> kern  :warn  : [    2.939636] ------------[ cut here ]------------
> kern  :warn  : [    2.944436] Your BIOS is broken; bad RMRR [0x00000000a1800000-0x00000000a3ffffff]
>                               BIOS vendor: Dell Inc.; Ver: 1.2.8; Product Version: 


The e820 map has this:

> kern  :info  : [    0.000000] BIOS-e820: [mem 0x00000000a0000000-0x00000000a00fffff] reserved
> kern  :info  : [    0.000000] BIOS-e820: [mem 0x00000000f8000000-0x00000000fbffffff] reserved
> kern  :info  : [    0.000000] BIOS-e820: [mem 0x00000000fe000000-0x00000000fe010fff] reserved

The region 0xa1800000-0xa3ffffff isn't explicitly reserved (it's not 
listed at all), which the IOMMU-folk say is the fault of the firmware.

My commit made it so that it merely spits out a warning, instead of 
failing to use the IOMMU at all.

Thanks,

Barret