[Bug 112256] New: i915, git bisect, 5.4-rc1: corrupted page table using ply-image after "drm/i915: Disregard drm_mode_config.fb_base"

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=112256

            Bug ID: 112256
           Summary: i915, git bisect, 5.4-rc1: corrupted page table using
                    ply-image after "drm/i915: Disregard
                    drm_mode_config.fb_base"
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: not set
          Priority: not set
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: freedesktop at nmacleod.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 145944
  --> https://bugs.freedesktop.org/attachment.cgi?id=145944&action=edit
5.4-rc7 with corrupted page table trace

Testing on a Skylake NUC6i5SYH.

In LibreELEC we use plymouth-lite[1] to display a splash image (png) during
initrd.

Since 5.4-rc1 whenever ply-image is executed the kernel produces a corrupted
page table trace and the png image does not appear (as ply-image fails):

[    1.712976] ply-image: Corrupted page table at address 7f4f8f2fffe0
[    1.712999] PGD 80000001cbe3c067 P4D 80000001cbe3c067 PUD 2727a6067 PMD
1cbcec067 PTE 800fbfa2307e8237
[    1.713024] Bad pagetable: 000f [#1] SMP PTI
[    1.713035] CPU: 2 PID: 272 Comm: ply-image Not tainted 5.4.0-rc7 #1
[    1.713052] Hardware name:  /NUC6i5SYB, BIOS
SYSKLi35.86A.0063.2017.1115.1550 11/15/2017
[    1.713073] RIP: 0033:0x7f4f8fd8240e
[    1.713083] Code: ff ff 0f 18 89 40 fe ff ff c5 fe 6f 01 c5 fe 6f 49 e0 c5
fe 6f 51 c0 c5 fe 6f 59 a0 48 81 e9 80 00 00 00 48 81 ea 80 00 00 00 <c4> c1 7d
e7 01 c4 c1 7d e7 49 e0 c4 c1 7d e7 51 c0 c4 c1 7d e7 59
[    1.713129] RSP: 002b:00007fff9e3a6e68 EFLAGS: 00010202
[    1.713143] RAX: 00007f4f8eb17000 RBX: 00000000006454f0 RCX:
00007f4f8eb15f70
[    1.713161] RDX: 00000000007e8f80 RSI: 00007f4f8e32d010 RDI:
00007f4f8eb17000
[    1.713178] RBP: 00000000006454f0 R08: 0000000000000000 R09:
00007f4f8f2fffe0
[    1.713195] R10: 00007f4f8f2feff0 R11: 00007f4f8f2fffe0 R12:
00000000006455d0
[    1.713213] R13: 0000000000000780 R14: 00007f4f8db43010 R15:
0000000000000000
[    1.713231] FS:  00007f4f8faea740 GS:  0000000000000000
[    1.713245] Modules linked in:
[    1.713254] ---[ end trace a347200260b0a1b5 ]---
[    1.713269] RIP: 0033:0x7f4f8fd8240e
[    1.713284] Code: ff ff 0f 18 89 40 fe ff ff c5 fe 6f 01 c5 fe 6f 49 e0 c5
fe 6f 51 c0 c5 fe 6f 59 a0 48 81 e9 80 00 00 00 48 81 ea 80 00 00 00 <c4> c1 7d
e7 01 c4 c1 7d e7 49 e0 c4 c1 7d e7 51 c0 c4 c1 7d e7 59
[    1.713328] RSP: 002b:00007fff9e3a6e68 EFLAGS: 00010202
[    1.713341] RAX: 00007f4f8eb17000 RBX: 00000000006454f0 RCX:
00007f4f8eb15f70
[    1.713358] RDX: 00000000007e8f80 RSI: 00007f4f8e32d010 RDI:
00007f4f8eb17000
[    1.713375] RBP: 00000000006454f0 R08: 0000000000000000 R09:
00007f4f8f2fffe0
[    1.713392] R10: 00007f4f8f2feff0 R11: 00007f4f8f2fffe0 R12:
00000000006455d0
[    1.713410] R13: 0000000000000780 R14: 00007f4f8db43010 R15:
0000000000000000
[    1.713428] FS:  00007f4f8faea740(0000) GS:ffffa35575b00000(0000)
knlGS:0000000000000000
[    1.713448] CS:  0033 DS: 0000 ES: 0000 CR0: 0000000080050033

(full log with drm.debug=0xe attached)

Bisecting the kernel from 5.3.0 (good) to 5.4-rc1 (bad) identifies the first
bad commit as:

drm/i915: Disregard drm_mode_config.fb_base[2]

Reverting this commit[2] stops the trace appearing with all kernels 5.4-rc1
through to 5.4-rc7, and ply-image now successfully displays the splash image.

I have tested drm-tip[3] and this also produces the same trace as 5.4-rc with
the bad commit[2] is present.

This version of plymouth-lite[1] is working fine with all kernels prior to
5.4-rc1.

Is this a plymouth-lite issue, or a kernel 5.4 issue? 

Thanks.

1. http://sources.libreelec.tv/devel/plymouth-lite-0.6.0.tar.bz2
2.
https://github.com/torvalds/linux/commit/5f889b9a61dd7069e61d0328bc514f0f508328c1
3.
https://cgit.freedesktop.org/drm-tip/commit/?id=dd07789205270dd69eca30ef7d123b5d2322d7a8

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