[Qemu-devel] [Bug 1811244] Re: qemu 3.1/i386 crashes/guest hangs when MTTCG is enabled

[Jakub Jermar]

As for the other outcome, when the guest hangs (instead of QEMU
crashing), the guest CPUs that block forward progress are halted in an
idle loop, have interrupts enabled and have a queued timer IRQ 248 and a
pending software IPI IRQ 250. It appears another timer IRQ is currently
being serviced (but the CPU is idling).

(qemu) cpu 1
(qemu) info registers
EAX=ff8b7000 EBX=ff8b7000 ECX=00000003 EDX=00000003
ESI=00000001 EDI=ff8b5240 EBP=ff8b7000 ESP=ff8b7fac
EIP=f0029707 EFL=00000202 [-------] CPL=0 II=0 A20=1 SMM=0 HLT=1
ES =0023 00000000 ffffffff 00cff300 DPL=3 DS   [-WA]
CS =0008 00000000 ffffffff 00cf9b00 DPL=0 CS32 [-RA]
SS =0010 00000000 ffffffff 00cf9300 DPL=0 DS   [-WA]
DS =0023 00000000 ffffffff 00cff300 DPL=3 DS   [-WA]
FS =0023 00000000 ffffffff 00cff300 DPL=3 DS   [-WA]
GS =0023 00000000 ffffffff 00cff300 DPL=3 DS   [-WA]
LDT=0000 00000000 00000000 00008200 DPL=0 LDT
TR =0068 efbfe280 00003d80 00008900 DPL=0 TSS32-avl
GDT=     ffbd8400 00000077
IDT=     eacfe000 000007ff
CR0=8001003b CR2=00000000 CR3=03fde000 CR4=00000690
DR0=00000000 DR1=00000000 DR2=00000000 DR3=00000000 
DR6=ffff0ff0 DR7=00000400
EFER=0000000000000000
FCW=037f FSW=0000 [ST=0] FTW=00 MXCSR=00001f80
FPR0=0000000000000000 0000 FPR1=0000000000000000 0000
FPR2=0000000000000000 0000 FPR3=0000000000000000 0000
FPR4=0000000000000000 0000 FPR5=0000000000000000 0000
FPR6=0000000000000000 0000 FPR7=0000000000000000 0000
XMM00=00000000000000000000000000000000 XMM01=00000000000000000000000000000000
XMM02=00000000000000000000000000000000 XMM03=00000000000000000000000000000000
XMM04=00000000000000000000000000000000 XMM05=00000000000000000000000000000000
XMM06=00000000000000000000000000000000 XMM07=00000000000000000000000000000000
(qemu) info lapic
dumping local APIC state for CPU 1 

LVT0     0x0001003f active-hi edge  masked                      Fixed  (vec 63)
LVT1     0x0001003f active-hi edge  masked                      Fixed  (vec 63)
LVTPC    0x000100ff active-hi edge  masked                      Fixed  (vec 255)
LVTERR   0x000000fb active-hi edge                              Fixed  (vec 251)
LVTTHMR  0x000100ff active-hi edge  masked                      Fixed  (vec 255)
LVTT     0x000200f8 active-hi edge                 periodic     Fixed  (vec 248)
Timer    DCR=0xb (divide by 1) initial_count = 997376
SPIV     0x00000107 APIC enabled, focus=off, spurious vec 7
ICR      0x00000000 physical edge de-assert no-shorthand
ICR2     0x00000000 cpu 0 (APIC ID)
ESR      0x00000000
ISR      248 
IRR      248 250 

APR 0x00 TPR 0x00 DFR 0x0f LDR 0x00 PPR 0xf0

(gdb) set $eip=f0029707
(gdb) set $esp=ff8b7fac
(gdb) bt
#0  0xf0029707 in Proc::halt () at 
/home/jermar/Kernkonzept/software/l4/fiasco/src/drivers/ia32/processor-ia32.cpp:47
#1  0xf00193b8 in Kernel_thread::idle_op (address@hidden) at 
/home/jermar/Kernkonzept/software/l4/fiasco/src/kern/kernel_thread.cpp:134
#2  0xf001bc11 in call_ap_bootstrap (this=0xffb66da4, resume=0xf001bc11) at 
/home/jermar/Kernkonzept/software/l4/fiasco/src/kern/app_cpu_thread.cpp:111
#3  0x00000001 in ?? ()

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https://bugs.launchpad.net/bugs/1811244

Title:
  qemu 3.1/i386 crashes/guest hangs when MTTCG is enabled

Status in QEMU:
  New

Bug description:
  When MTTCG is enabled, QEMU 3.1.0 sometimes crashes when running the
  following command line:

  qemu-system-i386 -kernel
  /home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/bootstrap
  -append bootstrap -initrd
  "/home/jermar/work/software/l4/fiasco/.build-i386/fiasco
  
-serial_esc,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f/sigma0
  ,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f/moe
  
rom/ahci.cfg,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f/ned
  ,test_env.lua ,/home/jermar/Kernkonzept/software/l4/pkg/ahci-
  driver/examples/md5sum/ahci.cfg
  ,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f/l4re
  ,/home/jermar/Kernkonzept/software/l4/pkg/ahci-
  driver/examples/md5sum/ahci.io
  ,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f/io
  ,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f
  /ahci-drv
  ,/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x86_gen/l4f
  /ahci-md5-sync" -smp 4 -accel tcg,thread=multi -device ahci,id=ahci0
  -drive
  if=none,file=/home/jermar/Kernkonzept/software/l4/.build-i386/pkg
  /ahci-driver/test/examples/test_ahci.img,format=raw,id=drive-sata0-0-0
  -device ide-drive,bus=ahci0.0,drive=drive-sata0-0-0,id=sata0-0-0
  -serial stdio -nographic -monitor none

  The host is x86_64.

  The stack at the time of the crash (core dump and debug binary
  attached to the bug):

  Core was generated by `qemu-system-i386 -kernel 
/home/jermar/Kernkonzept/software/l4/.build-i386/bin/x'.
  Program terminated with signal SIGSEGV, Segmentation fault.
  #0  io_writex (address@hidden, address@hidden, mmu_idx=2, address@hidden, 
address@hidden, address@hidden, recheck=false, size=4)
      at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/cputlb.c:791
  791       if (mr->global_locking && !qemu_mutex_iothread_locked()) {
  [Current thread is 1 (Thread 0x7fc5af7fe700 (LWP 3625719))]
  Missing separate debuginfos, use: dnf debuginfo-install 
SDL2-2.0.9-1.fc29.x86_64 at-spi2-atk-2.30.0-1.fc29.x86_64 
at-spi2-core-2.30.0-2.fc29.x86_64 atk-2.30.0-1.fc29.x86_64 
bzip2-libs-1.0.6-28.fc29.x86_64 cairo4
  (gdb) bt
  #0  0x0000565354f5f365 in io_writex
      (address@hidden, address@hidden, mmu_idx=2, address@hidden, 
address@hidden, address@hidden, recheck=false, size=4)
      at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/cputlb.c:791
  #1  0x0000565354f621b2 in io_writel (recheck=<optimized out>, 
retaddr=140487132809203, addr=3938451632, val=0, index=0, mmu_idx=2, 
env=0x565355ca0140)
      at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/softmmu_template.h:310
  #2  0x0000565354f621b2 in helper_le_stl_mmu (env=0x565355ca0140, 
addr=<optimized out>, val=0, oi=34, retaddr=140487132809203)
      at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/softmmu_template.h:310
  #3  0x00007fc5b5a587f3 in code_gen_buffer ()
  #4  0x0000565354f75fd0 in cpu_tb_exec (itb=<optimized out>, 
cpu=0x7fc5b5a5aa40 <code_gen_buffer+12266006>) at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/cpu-exec.c:171
  #5  0x0000565354f75fd0 in cpu_loop_exec_tb (tb_exit=<synthetic pointer>, 
last_tb=<synthetic pointer>, tb=<optimized out>, cpu=0x7fc5b5a5aa40 
<code_gen_buffer+12266006>)
      at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/cpu-exec.c:615
  #6  0x0000565354f75fd0 in cpu_exec (address@hidden) at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/accel/tcg/cpu-exec.c:725
  #7  0x0000565354f33b1f in tcg_cpu_exec (cpu=0x565355c97e90) at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/cpus.c:1429
  #8  0x0000565354f35e83 in qemu_tcg_cpu_thread_fn (arg=0x565355c97e90) at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/cpus.c:1733
  #9  0x0000565354f35e83 in qemu_tcg_cpu_thread_fn (address@hidden) at 
/home/jermar/software/HelenOS/helenos.git/contrib/qemu/qemu-3.1.0/cpus.c:1707
  #10 0x00005653552ec5da in qemu_thread_start (args=<optimized out>) at 
util/qemu-thread-posix.c:498
  #11 0x00007fc5b858a58e in start_thread () at /lib64/libpthread.so.0
  #12 0x00007fc5b84b96a3 in clone () at /lib64/libc.so.6

  Another symptom that occurs more often than this crash is that the
  guest hangs while waiting for another CPU to complete a cross-CPU
  call. Disabling MTTCG makes both symptoms go away.

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