kern/49875: kernel crash with i915drmkms on Intel 82855GM

[dieter.NetBSD%pandora.be@localhost]

>Number:         49875
>Category:       kern
>Synopsis:       kernel crash with i915drmkms on Intel 82855GM
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun May 03 12:55:00 +0000 2015
>Originator:     dieter roelants
>Release:        NetBSD 7.0_BETA
>Organization:
>Environment:
System: NetBSD origin.amelgem.be 7.0_BETA NetBSD 7.0_BETA (GENERIC.201504302140Z) i386
Architecture: i386
Machine: i386
>Description:
	Starting Xorg (chrooted, but I assume it doesn't matter)
	on my laptop with "Intel 82855GM GMCH Integrated Graphics
	Device", the kernel crashes with following messages and bt:

warning: /usr/src/sys/external/bsd/drm2/dist/drm/i915/i915_gem.c:5689: list_empty(&obj->vma_list    
uvm_fault(0xc3429774, 0, 1) -> 0xe
fatal page fault in supervisor mode
trap type 6 code 0 eip c03d5c7a cs 8 eflags 13246 cr2 54 ilevel 0 esp c322fa00 
curlwp 0xc37fb2c0 pid 741 lid 1 lowest kstack 0xdbfca2c0
kernel: supervisor trap page fault, code=0
Stopped in pid 741.1 (Xorg) at  netbsd:i915_gem_object_pin_to_display_plane+0xb3:       movzbl  54(%
eax),%edx

db{0}> bt
i915_gem_object_pin_to_display_plane() at netbsd:i915_gem_object_pin_to_display_plane+0xb3
intel_pin_and_fence_fb_obj() at netbsd:intel_pin_and_fence_fb_obj+0x99
intel_pipe_set_base() at netbsd:intel_pipe_set_base+0x73
intel_crtc_set_config() at netbsd:intel_crtc_set_config+0x894 
drm_mode_set_config_internal() at netbsd:drm_mode_set_config_internal+0x4d
drm_mode_setcrtc() at netbsd:drm_mode_setcrtc+0xc6
drm_ioctl() at netbsd:drm_ioctl+0xff  
sys_ioctl() at netbsd:sys_ioctl+0x198 
syscall() at netbsd:syscall+0x7f 
--- syscall (number 54) ---
bb77bcc7:

	Kernel messages about the graphics device are:

agp0 at pchb0: i855-family chipset
agp0: detected 8060k stolen memory
agp0: aperture at 0xe8000000, size 0x8000000
i915drmkms0 at pci0 dev 2 function 0: Intel 82855GM GMCH Integrated Graphics Device (rev. 0x02)
drm: Memory usable by graphics device = 128M
drm: Supports vblank timestamp caching Rev 2 (21.10.2013).
drm: Driver supports precise vblank timestamp query.
i915drmkms0: interrupting at irq 9 (i915)
drm: GMBUS [i915 gmbus panel] timed out, falling back to bit banging on pin 3
drm: initialized overlay support
intelfb0 at i915drmkms0
i915drmkms0: info: registered panic notifier
intelfb0: framebuffer at 0xdadd4000, size 1400x1050, depth 32, stride 5632

>How-To-Repeat:
	Boot NetBSD 7.0_BETA, startx.
>Fix:
	The upstream commit 19656430a874132a1d79c56387a6eec1ef9a5689
	(See https://freedesktop.org/patch/26114/) stops the kernel
	from crashing, and results in an error message instead;
	"DRM error in intel_pipe_set_base: pin & fence failed".

	I also found that neither the crash nor the error (with
	patched kernel) occur when I `dd if=/dev/zeroof=/dev/null
	bs=512m count=1` before starting X, and it seems to be
	running ok. I haven't stressed it, though. Should I file
	a separate PR for this?