linux-kernel - Re: [BUG][REGRESSION] mangled display since -rc1

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Date:   Tue, 01 Nov 2016 12:27:15 +0100
From:   Martin Kepplinger <martink@...teo.de>
To:     Joerg Roedel <jroedel@...e.de>
CC:     Linux kernel <linux-kernel@...r.kernel.org>,
        torvalds@...ux-foundation.org, daniel.vetter@...el.com,
        jani.nikula@...ux.intel.com
Subject: Re: [BUG][REGRESSION] mangled display since -rc1



Am 31. Oktober 2016 22:54:54 MEZ, schrieb Joerg Roedel <jroedel@...e.de>:
>On Mon, Oct 31, 2016 at 09:44:51PM +0100, Martin Kepplinger wrote:
>> This is one machine booting a bad kernel. I could provide another
>> example later this week.
>
>You have an Intel system without any IOMMU (enabled), otherwise you
>would have a DMAR-ACPI table, but there is none:
>
>> [    0.000000] ACPI: RSDP 0x00000000000FE020 000024 (v02 ACRSYS)
>> [    0.000000] ACPI: XSDT 0x00000000A6FFE210 00008C (v01 ACRSYS
>ACRPRDCT 00000001      01000013)
>> [    0.000000] ACPI: FACP 0x00000000A6FFB000 0000F4 (v04 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: DSDT 0x00000000A6FEC000 00B903 (v01 ACRSYS
>ACRPRDCT 00000000 1025 00040000)
>> [    0.000000] ACPI: FACS 0x00000000A6FBB000 000040
>> [    0.000000] ACPI: FACS 0x00000000A6FBB000 000040
>> [    0.000000] ACPI: UEFI 0x00000000A6FFD000 000236 (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: ASF! 0x00000000A6FFC000 0000A5 (v32 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: HPET 0x00000000A6FFA000 000038 (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: APIC 0x00000000A6FF9000 00008C (v02 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: MCFG 0x00000000A6FF8000 00003C (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: SLIC 0x00000000A6FEB000 000176 (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: SSDT 0x00000000A6FEA000 0006FE (v01 ACRSYS
>ACRPRDCT 00001000 1025 00040000)
>> [    0.000000] ACPI: BOOT 0x00000000A6FE8000 000028 (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: ASPT 0x00000000A6FE3000 000034 (v07 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: FPDT 0x00000000A6FE1000 000044 (v01 ACRSYS
>ACRPRDCT 00000001 1025 00040000)
>> [    0.000000] ACPI: SSDT 0x00000000A6FE0000 00079A (v01 ACRSYS
>ACRPRDCT 00003000 1025 00040000)
>> [    0.000000] ACPI: SSDT 0x00000000A6FDF000 000A92 (v01 ACRSYS
>ACRPRDCT 00003000 1025 00040000)
>
>So it is pretty unlikely that any change in IOMMU code causes your
>issue. Not sure why your bisecting ended up there. You also have an
>Intel GPU in the system:
>
>> 00:02.0 VGA compatible controller: Intel Corporation 2nd Generation
>Core Processor Family Integrated Graphics Controller (rev 09) (prog-if
>00 [VGA controller])
>> 	Subsystem: Acer Incorporated [ALI] Device 0748
>> 	Flags: bus master, fast devsel, latency 0, IRQ 28
>> 	Memory at c0000000 (64-bit, non-prefetchable) [size=4M]
>> 	Memory at b0000000 (64-bit, prefetchable) [size=256M]
>> 	I/O ports at 2000 [size=64]
>> 	[virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
>> 	Capabilities: <access denied>
>> 	Kernel driver in use: i915
>
>My best guess is that some changes in the i915 driver cause your issue,
>I add the maintainers of i915 to the cc-list, maybe they have an idea.
>
>
>	Joerg


I'll come up with a nouveau system example and it was quite easy to bisect. To quote the merge commit msg:

This also required some changes outside of the IOMMU code, but these are acked by the respective maintainers.

Any help on bisecting into it would be awesome.