On 2016-04-06 10:55, Andrew Cooper wrote:
On 06/04/16 00:57, Mihai Donțu wrote:
On Wed, 06 Apr 2016 01:38:32 +0200 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'.
According to Xen IRC channel, the cause could be a bug in the x86
instruction emulator related to SSE.
I don't believe the x86 emulator is complete wrt the SSE instruction
set. But I do wonder why, in your case, these instructions need
emulation at all. Unless touching the video RAM requires emulation.
Can
you try using a different video driver? I see xorg picked up qxl,
maybe
try vesa?
Now I think about it, even dirty VRAM tracking shouldn't actually
emulate the instructions.
Can you grab the full register state at the point of Xorgs crash?
`info
regs` in gdb?
The instruction in use, `movaps` is specified to fault if the memory
operand isn't aligned on a 16byte boundary. Therefore, if %rax in this
case isn't a multiple of 16, this is a code generation bug, rather than
an emulation bug.
~Andrew
Attached is the full register state.
I'm very interested in getting to the bottom of this, so please let me
know if I can do anything to help.
(gdb) info registers
rax 0xf1fe000001e000 68114745340846080
rbx 0x9 9
rcx 0xfffffc00 4294966272
rdx 0x222222 2236962
rsi 0x7fc650541000 140489727938560
rdi 0x7fc65b3ee420 140489911100448
rbp 0x16 0x16
rsp 0x7ffcad040b58 0x7ffcad040b58
r8 0x400 1024
r9 0x20 32
r10 0x20 32
r11 0x9 9
r12 0x4 4
r13 0xffffffff 4294967295
r14 0x55dff82d8820 94420429801504
r15 0x55dff82d80c0 94420429799616
rip 0x7fc65c3d5626 0x7fc65c3d5626 <sse2_blt+1159>
eflags 0x13206 [ PF IF #12 #13 RF ]
cs 0x33 51
ss 0x2b 43
ds 0x0 0
es 0x0 0
fs 0x0 0
gs 0x0 0
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
