On 2016-05-18 11:12, Jan Beulich wrote:
On 06.04.16 at 01:38, <wo...@openmailbox.org> wrote:
I'm running Xen 4.6.1 with Alpine Linux 3.3.3 in dom0. In a HVM domU
with vga="qxl", Xorg will segfault instantly if tried started.
Multiple
Linux distros have been tested and Xorg segfaults in all.
Attached are a full backtrace from domU generated by Xorg, and a
assembler dump of function 'sse2_blt'.
Just FYI: Looks like I can repro this finally, and it also looks like
at
least for me it isn't an SSE2 instruction that the issue is with.
Instead I'm getting an #UD in the middle of an instruction a few
lines down from the last SSE2 one, which suggests we're having
an issue with sizing instructions (however odd that may seem).
Now that I can repro it, at least I have something to actually
debug ...
Jan
I have patched Xen 4.6.1 with commit
2bb230972c5ddb1ca823f47750b5d46a9d302d0e
(x86emul: suppress writeback upon unsuccessful MMX/SSE/AVX insn
emulation) and
tested with different Linux distros. I can say with confidence that the
patch
has solved my initial problem as Xorg no longer segfaults when started.
Thanks
to everyone that has helped with this.
However, while testing I have found a new problem. This may not be
related to
my initial problem or even Xen, but I will try to describe it here as
I'm hoping
someone can point me in the right direction.
Various actions will now raise the CPU usage of Xorg to 100% and freeze
the
entire X Window System for some time. E.g.:
Starting xterm in a window manager or directly from .xinitrc and
executing
dmesg. This will print a few lines per second while the Xorg CPU usage
is 100%
and the X Window System is frozen for about 60 seconds until all dmesg
output
has been printed.
I have run 'perf record -g -a sleep 60' while connected via SSH and then
executed dmesg in xterm. I have attached a few lines of 'perf report -g'
with
the first one expanded.
I have also run 'strace -p $(pidof Xorg)' while dmesg was running in
xterm. The
lines I have attached will repeat until all dmesg output has been
printed. File
descriptor 8 is pointing on '/dev/dri/card0'.
Any ideas on what could cause this?
William Z.
Samples: 239K of event 'cpu-clock', Event count (approx.): 5999200
Children Self Command Shared Object Symbol
- 98.63%98.53% Xorglibpixman-1.so.0.33.6 [.] sse2_blt.part.0
- sse2_blt.part.0
- 0.10% xen_hvm_callback_vector
xen_evtchn_do_upcall
irq_exit
__do_softirq
run_timer_softirq
call_timer_fn
rh_timer_func
- usb_hcd_poll_rh_status
- 0.10% uhci_hub_status_data
_raw_spin_unlock_irqrestore
0.00% mod_timer
- 0.00% retint_user
prepare_exit_to_usermode
exit_to_usermode_loop
schedule
__schedule
finish_task_switch
+0.57% 0.00% Xorg[kernel.kallsyms] [k]
entry_SYSCALL_64_fastpath
+0.51% 0.00% Xorglibc-2.23.so [.] __GI___ioctl
+0.51% 0.00% Xorg[kernel.kallsyms] [k] sys_ioctl
+0.51% 0.00% swapper [kernel.kallsyms] [k] rest_init
+0.51% 0.00% swapper [kernel.kallsyms] [k] start_kernel
+0.51% 0.00% swapper [kernel.kallsyms] [k]
x86_64_start_reservations
+0.51% 0.00% swapper [kernel.kallsyms] [k]
x86_64_start_kernel
+0.50% 0.00% swapper [kernel.kallsyms] [k]
cpu_startup_entry
+0.50% 0.00% Xorg[kernel.kallsyms] [k] do_vfs_ioctl
--- SIGALRM {si_signo=SIGALRM, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]}) = 14965392016
ioctl(8, DRM_IOCTL_QXL_ALLOC, 0x7ffce28a6780) = 0
ioctl(8, DRM_IOCTL_QXL_MAP, 0x7ffce28a6780) = 0
mmap(NULL, 13436, PROT_READ|PROT_WRITE, MAP_SHARED, 8, 0x107931000) =
0x7f5489ddb000
ioctl(8, DRM_IOCTL_QXL_ALLOC, 0x7ffce28a6780) = 0
ioctl(8, DRM_IOCTL_QXL_MAP, 0x7ffce28a6780) = 0
mmap(NULL, 48, PROT_READ|PROT_WRITE, MAP_SHARED, 8, 0x107935000) =
0x7f5489dda000
ioctl(8, DRM_IOCTL_QXL_EXECBUFFER, 0x7ffce28a6830) = 0
munmap(0x7f5489ddb000, 13436) = 0
ioctl(8, DRM_IOCTL_GEM_CLOSE, 0x7ffce28a6800) = 0
munmap(0x7f5489dda000, 48) = 0
ioctl(8, DRM_IOCTL_GEM_CLOSE, 0x7ffce28a6860) = 0
setitimer(ITIMER_REAL, {it_interval={0, 0}, it_value={0, 0}}, NULL) = 0
select(512, [1 3 4 5 6 9], NULL, NULL, {0, 0}) = 0 (Timeout)
setitimer(ITIMER_REAL, {it_interval={0, 5000}, it_value={0, 5000}}, NULL) = 0
clock_gettime(CLOCK_MONOTONIC, {5298, 406984775}) = 0
ioctl(8, DRM_IOCTL_QXL_UPDATE_AREA, 0x7ffce28a6820) = 0
--- SIGALRM {si_signo=SIGALRM, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]}) = 14965411184
--- SIGALRM {si_signo=SIGALRM, si_code=SI_KERNEL} ---
rt_sigreturn({mask=[]}) = 14965435536
ioctl(8, DRM_IOCTL_QXL_ALLOC
