[REGRESSION] Panic in gen8_ggtt_insert_entries() with v6.5

[Oleksandr Natalenko <oleksandr@natalenko.name>]

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Hello.

Since v6.5 kernel the following HW:

* Lenovo T460s laptop with Skylake GT2 [HD Graphics 520] (rev 07)
* Lenovo T490s laptop with WhiskeyLake-U GT2 [UHD Graphics 620] (rev 02)

is affected by the following crash once KDE on either X11 or Wayland is started:

i915 0000:00:02.0: enabling device (0006 -> 0007)
i915 0000:00:02.0: vgaarb: deactivate vga console
i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=mem
i915 0000:00:02.0: [drm] Finished loading DMC firmware i915/skl_dmc_ver1_27.bin (v1.27)
[drm] Initialized i915 1.6.0 20201103 for 0000:00:02.0 on minor 1
fbcon: i915drmfb (fb0) is primary device
i915 0000:00:02.0: [drm] fb0: i915drmfb frame buffer device
…
memfd_create() without MFD_EXEC nor MFD_NOEXEC_SEAL, pid=674 'kwin_wayland'
BUG: unable to handle page fault for address: ffffb422c2800000
#PF: supervisor write access in kernel mode
#PF: error_code(0x0002) - not-present page
PGD 100000067 P4D 100000067 PUD 1001df067 PMD 10d1cf067 PTE 0
Oops: 0002 [#1] PREEMPT SMP PTI
CPU: 1 PID: 674 Comm: kwin_wayland Not tainted 6.5.0-pf1 #1 a6c58ff41a7b8bb16a19f5af9e0e9bce20f9f38d
Hardware name: LENOVO 20FAS2BM0F/20FAS2BM0F, BIOS N1CET90W (1.58 ) 11/15/2022
RIP: 0010:gen8_ggtt_insert_entries+0xc2/0x140 [i915]
…
Call Trace:
 <TASK>
 intel_ggtt_bind_vma+0x3e/0x60 [i915 a83fdc6539431252dba13053979a8b680af86836]
 i915_vma_bind+0x216/0x4b0 [i915 a83fdc6539431252dba13053979a8b680af86836]
 i915_vma_pin_ww+0x405/0xa80 [i915 a83fdc6539431252dba13053979a8b680af86836]
 __i915_ggtt_pin+0x5a/0x130 [i915 a83fdc6539431252dba13053979a8b680af86836]
 i915_ggtt_pin+0x78/0x1f0 [i915 a83fdc6539431252dba13053979a8b680af86836]
 __intel_context_do_pin_ww+0x312/0x700 [i915 a83fdc6539431252dba13053979a8b680af86836]
 i915_gem_do_execbuffer+0xfc6/0x2720 [i915 a83fdc6539431252dba13053979a8b680af86836]
 i915_gem_execbuffer2_ioctl+0x111/0x260 [i915 a83fdc6539431252dba13053979a8b680af86836]
 drm_ioctl_kernel+0xca/0x170
 drm_ioctl+0x30f/0x580
 __x64_sys_ioctl+0x94/0xd0
 do_syscall_64+0x5d/0x90
 entry_SYSCALL_64_after_hwframe+0x6e/0xd8
…
note: kwin_wayland[674] exited with irqs disabled

RIP seems to translate into this:

$ scripts/faddr2line drivers/gpu/drm/i915/gt/intel_ggtt.o gen8_ggtt_insert_entries+0xc2
gen8_ggtt_insert_entries+0xc2/0x150:
writeq at /home/pf/work/devel/own/pf-kernel/linux/./arch/x86/include/asm/io.h:99
(inlined by) gen8_set_pte at /home/pf/work/devel/own/pf-kernel/linux/drivers/gpu/drm/i915/gt/intel_ggtt.c:257
(inlined by) gen8_ggtt_insert_entries at /home/pf/work/devel/own/pf-kernel/linux/drivers/gpu/drm/i915/gt/intel_ggtt.c:300

Probably, recent PTE-related changes are relevant:

$ git log --oneline --no-merges v6.4..v6.5 -- drivers/gpu/drm/i915/gt/intel_ggtt.c
3532e75dfadcf drm/i915/uc: perma-pin firmwares
4722e2ebe6f21 drm/i915/gt: Fix second parameter type of pre-gen8 pte_encode callbacks
9275277d53248 drm/i915: use pat_index instead of cache_level
5e352e32aec23 drm/i915: preparation for using PAT index
341ad0e8e2542 drm/i915/mtl: Add PTE encode function

Also note Lenovo T14s laptop with TigerLake-LP GT2 [Iris Xe Graphics] (rev 01) is not affected by this issue.

Full dmesg with DRM debug enabled is available in the bugreport I've reported earlier [1]. I'm sending this email to make the issue more visible.

Please help.

Thanks.

[1] https://gitlab.freedesktop.org/drm/intel/-/issues/9256

-- 
Oleksandr Natalenko (post-factum)

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