Re: Fbdev graphics broken in xen/next dom0

[Arvind R <arvino55@gmail.com>]

On Fri, Mar 26, 2010 at 5:25 AM, Eamon Walsh <ewalsh@tycho.nsa.gov> wrote:
> On 03/16/2010 06:19 PM, Konrad Rzeszutek Wilk wrote:
< --- snip --- >
> I have attached the serial console output and dmesg output.  The
> initcall and drm debug stuff is present.
>
> Also, I get something new when I run the test program.  It prints out:
>
> # ./silly
> Mapped /dev/fb0 at 0x7f3237175000
> Killed
>
> Message from syslogd@moss-flapper at Mar 25 19:25:52 ...
>  kernel:Bad pagetable: 000f [#1] SMP
>
< --- snip --- >
> silly: Corrupted page table at address 7f3237175000
> PGD 1deaec067 PUD 1db6d1067 PMD 1da569067 PTE fffffffffffff22f
> Bad pagetable: 000f [#1] SMP
> last sysfs file: /sys/devices/system/cpu/cpu3/cache/index2/shared_cpu_map
> CPU 1
> Modules linked in: nfs fscache bridge stp llc ipt_MASQUERADE iptable_nat nf_nat nfsd lockd nfs_acl auth_rpcgss export]
< --- snip --->
>>> [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on minor 0
>>>
>> You look to have a i915 framebuffer on your box.
>>
>> I *think* that the i915 is not using KMS and the TTM stuff, so the
>> patch that Arvind posted would probably not help you.
>> http://www.mail-archive.com/dri-devel@lists.sourceforge.net/msg48668.html
>>
>> So, lets boot your kernel with these command line parameters to get more
>> data: debug initcall_debug drm.debug=255

< --- snip --- >

>> e-mail thread titled: "Nouveau on dom0". It covers the gamma of things
>> to troubleshoot this.

This is related and most probably due to the same bit. xf86-video-fbdev works
on bare-metal boot on XenNext with the nouveaufb driver but not on Xen.
Have upgraded whole chain to tip except xen which is 3.4.3rc3
Here is the syslog trace:
kernel: ------------[ cut here ]------------
kernel: WARNING: at arch/x86/mm/pat.c:872 track_pfn_vma_copy+0x4d/0x86()
kernel: Hardware name: System Product Name
kernel: Modules linked in: fbcon font bitblit softcursor nouveau ttm
drm_kms_helper drm cfbcopyarea cfbimgblt cfbfillrect bridge stp llc
ipv6 nfsd lockd nfs_acl auth_rpcgss sunrpc exportfs fuse
kernel: Pid: 5835, comm: Xorg Not tainted 2.6.32-xen0-git20100323+asusp5wd #1
kernel: Call Trace:
kernel:  [<ffffffff8102c834>] ? track_pfn_vma_copy+0x4d/0x86
kernel:  [<ffffffff8102c834>] ? track_pfn_vma_copy+0x4d/0x86
kernel:  [<ffffffff8103ce54>] ? warn_slowpath_common+0x77/0xa3
kernel:  [<ffffffff8102c834>] ? track_pfn_vma_copy+0x4d/0x86
kernel:  [<ffffffff8100c436>] ? xen_leave_lazy_mmu+0x25/0x43
kernel:  [<ffffffff81090c49>] ? copy_page_range+0x76/0x7f8
kernel:  [<ffffffff8100ddc9>] ? xen_force_evtchn_callback+0x9/0xa
kernel:  [<ffffffff8100e572>] ? check_events+0x12/0x20
kernel:  [<ffffffff8100e55f>] ? xen_restore_fl_direct_end+0x0/0x1
kernel:  [<ffffffff8103b1f2>] ? dup_mm+0x276/0x409
kernel:  [<ffffffff8103bd82>] ? copy_process+0x9c8/0x10ff
kernel:  [<ffffffff8103c5ff>] ? do_fork+0x146/0x2c0
kernel:  [<ffffffff810110a3>] ? stub_clone+0x13/0x20
kernel:  [<ffffffff81010d82>] ? system_call_fastpath+0x16/0x1b
kernel: ---[ end trace c58bf004d15b0c42 ]---

Xorg.log ends with the same message as originally with trying
accelerated nouveau with misleading
XKB: Failed to compile keymap

fbdev.c calls fbdevHWMapVidmem in xorg-server/hw/xfree86/fbdevhw.c
which does a mmap as in silly.c.  As far as X is concerned, everything
is fine, but there is obviously a page-fault problem. Will have to setup
debug options and trace :-(

The 'corrupted page table' syndrome is also present in the accelerated
nouveau with AGP cards - so it may be linked to this problem. At least
this problem can be repeated on many platforms :-)