Re: [Qemu-devel] [PATCH 15/18] Boot Linux Console Test: add a test for aarch64 + virt

[Cleber Rosa <crosa@redhat.com>]

On Fri, Jun 07, 2019 at 12:26:48AM -0300, Eduardo Habkost wrote:
> On Fri, Feb 01, 2019 at 11:10:31AM -0500, Cleber Rosa wrote:
> > 
> > 
> > On 1/31/19 4:26 PM, Cleber Rosa wrote:
> > > 
> > > 
> > > On 1/31/19 3:21 PM, Cleber Rosa wrote:
> > >>
> > >>
> > >> On 1/31/19 3:02 PM, Wainer dos Santos Moschetta wrote:
> > >>>
> > >>> On 01/17/2019 04:56 PM, Cleber Rosa wrote:
> > >>>> Just like the previous tests, boots a Linux kernel on a aarch64 target
> > >>>> using the virt machine.
> > >>>>
> > >>>> One special option added is the CPU type, given that the kernel
> > >>>> selected fails to boot on the virt machine's default CPU (cortex-a15).
> > >>>>
> > >>>> Signed-off-by: Cleber Rosa <crosa@redhat.com>
> > >>>> ---
> > >>>>   .travis.yml                            |  2 +-
> > >>>>   tests/acceptance/boot_linux_console.py | 20 ++++++++++++++++++++
> > >>>>   2 files changed, 21 insertions(+), 1 deletion(-)
> > >>>>
> > >>>> diff --git a/.travis.yml b/.travis.yml
> > >>>> index 54100eea5a..595e8c0b6c 100644
> > >>>> --- a/.travis.yml
> > >>>> +++ b/.travis.yml
> > >>>> @@ -187,7 +187,7 @@ matrix:
> > >>>>         # Acceptance (Functional) tests
> > >>>>       - env:
> > >>>> -        - CONFIG="--python=/usr/bin/python3
> > >>>> --target-list=x86_64-softmmu,mips-softmmu,mips64el-softmmu,ppc64-softmmu"
> > >>>> +        - CONFIG="--python=/usr/bin/python3
> > >>>> --target-list=x86_64-softmmu,mips-softmmu,mips64el-softmmu,ppc64-softmmu,aarch64-softmmu"
> > >>>>
> > >>>>           - TEST_CMD="make check-acceptance"
> > >>>>         addons:
> > >>>>           apt:
> > >>>> diff --git a/tests/acceptance/boot_linux_console.py
> > >>>> b/tests/acceptance/boot_linux_console.py
> > >>>> index f3ccd23a7a..107700b517 100644
> > >>>> --- a/tests/acceptance/boot_linux_console.py
> > >>>> +++ b/tests/acceptance/boot_linux_console.py
> > >>>> @@ -138,3 +138,23 @@ class BootLinuxConsole(Test):
> > >>>>           self.vm.launch()
> > >>>>           console_pattern = 'Kernel command line: %s' %
> > >>>> kernel_command_line
> > >>>>           self.wait_for_console_pattern(console_pattern)
> > >>>> +
> > >>>> +    def test_aarch64_virt(self):
> > >>>
> > >>> That test case fails on my system (Fedora 29 x86_64). Avocado seems
> > >>> unable to kill the VM so it  reaches the timeout.
> > >>>
> > >>> I compiled QEMU with default configuration:
> > >>>
> > >>> $ configure --python=/usr/bin/python3 --target-list=x86_64-softmmu
> > >>> --target-list=x86_64-softmmu,mips-softmmu,mips64el-softmmu,ppc64-softmmu,aarch64-softmmu)
> > >>>
> > >>>
> > >>> Follows a snippet of the Avocado's job.log file:
> > >>> ----
> > >>> 2019-01-31 14:41:34,912 test             L0602 INFO | START
> > >>> 07-/root/src/qemu/tests/acceptance/boot_linux_console.py:BootLinuxConsole.test_aarch64_virt
> > >>>
> > >>> 2019-01-31 14:41:34,912 test             L0298 DEBUG| DATA
> > >>> (filename=output.expected) => NOT FOUND (data sources: variant, test, file)
> > >>> 2019-01-31 14:41:34,913 parameters       L0146 DEBUG| PARAMS (key=arch,
> > >>> path=*, default=aarch64) => 'aarch64'
> > >>> 2019-01-31 14:41:34,913 parameters       L0146 DEBUG| PARAMS
> > >>> (key=qemu_bin, path=*, default=aarch64-softmmu/qemu-system-aarch64) =>
> > >>> 'aarch64-softmmu/qemu-system-aarch64'
> > >>> 2019-01-31 14:41:34,915 download         L0070 INFO | Fetching
> > >>> https://sjc.edge.kernel.org/fedora-buffet/fedora/linux/releases/29/Server/aarch64/os/images/pxeboot/vmlinuz
> > >>> -> /var/lib/avocado/data/cache/by_name/vmlinuz.3upct2pr
> > >>> 2019-01-31 14:41:35,490 download         L0054 DEBUG| Retrieved URL
> > >>> "https://sjc.edge.kernel.org/fedora-buffet/fedora/linux/releases/29/Server/aarch64/os/images/pxeboot/vmlinuz":
> > >>> content-length 8623423, date: "Thu, 31 Jan 2019 19:41:35 GMT",
> > >>> last-modified: "Sun, 21 Oct 2018 00:43:09 GMT"
> > >>> 2019-01-31 14:41:41,765 qemu             L0317 DEBUG| VM launch command:
> > >>> 'aarch64-softmmu/qemu-system-aarch64 -chardev
> > >>> socket,id=mon,path=/var/tmp/tmpizirkcud/qemu-32609-monitor.sock -mon
> > >>> chardev=mon,mode=control -display none -vga none -machine virt -chardev
> > >>> socket,id=console,path=/var/tmp/tmpizirkcud/qemu-32609-console.sock,server,nowait
> > >>> -serial chardev:console -cpu cortex-a53 -kernel
> > >>> /var/lib/avocado/data/cache/by_name/vmlinuz -append console=ttyAMA0'
> > >>> 2019-01-31 14:41:41,779 qmp              L0167 DEBUG| >>> {'execute':
> > >>> 'qmp_capabilities'}
> > >>> 2019-01-31 14:41:41,931 qmp              L0175 DEBUG| <<< {'return': {}}
> > >>> 2019-01-31 14:41:42,830 boot_linux_conso L0041 DEBUG| [    0.000000]
> > >>> Booting Linux on physical CPU 0x0000000000 [0x410fd034]
> > >>>
> > >>> (...)
> > >>>
> > >>> 2019-01-31 14:41:42,833 boot_linux_conso L0041 DEBUG| [    0.000000]
> > >>> Policy zone: DMA32
> > >>> 2019-01-31 14:41:42,833 boot_linux_conso L0041 DEBUG| [    0.000000]
> > >>> Kernel command line: console=ttyAMA0
> > >>> 2019-01-31 14:41:42,833 qmp              L0167 DEBUG| >>> {'execute':
> > >>> 'quit'}
> > >>
> > >> Here, a QMP response like "<<< {'return': {}}" would be expected.
> > >>
> > >> Since I can not reproduce this on my system (or on Travis-CI jobs I've
> > >> sent), can you tell me on top of which commit you've applied these patches?
> > >>
> > > 
> > > I spoke too soon:
> > > 
> > > https://travis-ci.org/clebergnu/qemu/jobs/487121425#L3033
> > > 
> > > This looks like a recent regression, and I'm guessing it's not on the
> > > test's side.  I'll try to bisect it and let you know.
> > > 
> > 
> > On a fresh environment, I am able to get this reproduced on every 2 of
> > runs, more or less.  When I hit it, I attached GDB to it, and the
> > backtrace shows:
> > 
> > Thread debugging using libthread_db enabled]
> > Using host libthread_db library "/lib64/libthread_db.so.1".
> > warning: Loadable section ".note.gnu.property" outside of ELF segments
> > warning: Loadable section ".note.gnu.property" outside of ELF segments
> > __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
> > 103     2:      movl    %edx, %eax
> > (gdb) bt
> > #0  __lll_lock_wait () at
> > ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:103
> > #1  0x00007fc6ba1a2e09 in __GI___pthread_mutex_lock
> > (mutex=mutex@entry=0x5615a233d020 <qemu_global_mutex>) at
> > ../nptl/pthread_mutex_lock.c:80
> > #2  0x00005615a1bb7593 in qemu_mutex_lock_impl (mutex=0x5615a233d020
> > <qemu_global_mutex>, file=0x5615a1db2d4c "util/main-loop.c", line=236)
> > at util/qemu-thread-posix.c:66
> > #3  0x00005615a171125e in qemu_mutex_lock_iothread_impl
> > (file=file@entry=0x5615a1db2d4c "util/main-loop.c", line=line@entry=236)
> > at /home/cleber/src/qemu/cpus.c:1849
> > #4  0x00005615a1bb415d in os_host_main_loop_wait (timeout=<optimized
> > out>) at util/main-loop.c:236
> > #5  main_loop_wait (nonblocking=<optimized out>) at util/main-loop.c:497
> > #6  0x00005615a18fdd39 in main_loop () at vl.c:1928
> > #7  0x00005615a16c9ee9 in main (argc=<optimized out>, argv=<optimized
> > out>, envp=<optimized out>) at vl.c:4665
> 
> Tip: run "thread apply all bt" so you can get a backtrace of all
> threads.
> 
>

Nice, thanks!

> > 
> > Running it with `taskset -c 1` prevents this issue from happening, which
> > AFAICT, contributes even further towards this being a QEMU race condition.
> > 
> > I'm CC'ing Peter and Claudio (listed maintainers of aarch64), as this
> > seems to limited to that target.  Any tips on what to do here?
> 
> I am hitting this on Travis, too, and I finally could reproduce
> it locally,
> 
> The guest is still writing on the serial console, but nobody is
> reading the data on the other side.  A VCPU thread is stuck
> inside the EAGAIN/nanosleep loop at qemu_chr_write_buffer(),
> holding the QEMU global lock.
>

This is awesome, because it really looks like a perfect explanation
for the behavior/reproducer/workaround that I described here:

 https://bugs.launchpad.net/qemu/+bug/1829779

> Thread 4 (Thread 0x7f2e45fff700 (LWP 6461)):
> #0  0x00007f2e4ec03500 in nanosleep () at /lib64/libpthread.so.0
> #1  0x00007f2e4fb229d7 in g_usleep () at /lib64/libglib-2.0.so.0
> #2  0x0000559a4e7ca4c9 in qemu_chr_write_buffer (s=s@entry=0x559a502d0ac0, buf=buf@entry=0x7f2e45ffdd90 "7", len=1, offset=offset@entry=0x7f2e45ffdd60, write_all=true) at chardev/char.c:115
> #3  0x0000559a4e7ca78f in qemu_chr_write (s=0x559a502d0ac0, buf=buf@entry=0x7f2e45ffdd90 "7", len=len@entry=1, write_all=write_all@entry=true) at chardev/char.c:148
> #4  0x0000559a4e7cc7e2 in qemu_chr_fe_write_all (be=be@entry=0x559a504b4c50, buf=buf@entry=0x7f2e45ffdd90 "7", len=len@entry=1) at chardev/char-fe.c:53
> #5  0x0000559a4e58f320 in pl011_write (opaque=0x559a504b47d0, offset=0, value=55, size=<optimized out>) at hw/char/pl011.c:183
> #6  0x0000559a4e325121 in memory_region_write_accessor (mr=0x559a504b4ae0, addr=0, value=<optimized out>, size=2, shift=<optimized out>, mask=<optimized out>, attrs=...) at /home/ehabkost/rh/proj/virt/qemu/memory.c:503
> #7  0x0000559a4e322cd6 in access_with_adjusted_size (addr=addr@entry=0, value=value@entry=0x7f2e45ffded8, size=size@entry=2, access_size_min=<optimized out>, access_size_max=<optimized out>, access_fn=access_fn@entry=
>     0x559a4e3250a0 <memory_region_write_accessor>, mr=0x559a504b4ae0, attrs=...) at /home/ehabkost/rh/proj/virt/qemu/memory.c:569
> #8  0x0000559a4e32763f in memory_region_dispatch_write (mr=mr@entry=0x559a504b4ae0, addr=addr@entry=0, data=<optimized out>, data@entry=55, size=size@entry=2, attrs=...) at /home/ehabkost/rh/proj/virt/qemu/memory.c:1497
> #9  0x0000559a4e338708 in io_writex (env=env@entry=0x559a503d5620, mmu_idx=mmu_idx@entry=1, val=val@entry=55, addr=addr@entry=18446462598867529728, retaddr=139836732143069, size=2, iotlbentry=<optimized out>, iotlbentry=<optimized out>)
>     at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cputlb.c:945
> #10 0x0000559a4e33d203 in store_helper (big_endian=false, size=2, retaddr=<optimized out>, oi=<optimized out>, val=55, addr=18446462598867529728, env=0x559a503d5620) at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cputlb.c:1544
> #11 0x0000559a4e33d203 in helper_le_stw_mmu (env=0x559a503d5620, addr=18446462598867529728, val=55, oi=<optimized out>, retaddr=139836732143069) at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cputlb.c:1636
> #12 0x00007f2e46bef5dd in code_gen_buffer ()
> #13 0x0000559a4e352381 in cpu_tb_exec (itb=<optimized out>, cpu=0x559a503d5620) at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cpu-exec.c:171
> #14 0x0000559a4e352381 in cpu_loop_exec_tb (tb_exit=<synthetic pointer>, last_tb=<synthetic pointer>, tb=<optimized out>, cpu=0x559a503d5620) at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cpu-exec.c:618
> #15 0x0000559a4e352381 in cpu_exec (cpu=cpu@entry=0x559a503cd360) at /home/ehabkost/rh/proj/virt/qemu/accel/tcg/cpu-exec.c:729
> #16 0x0000559a4e30ea0f in tcg_cpu_exec (cpu=0x559a503cd360) at /home/ehabkost/rh/proj/virt/qemu/cpus.c:1434
> #17 0x0000559a4e310b6b in qemu_tcg_cpu_thread_fn (arg=arg@entry=0x559a503cd360) at /home/ehabkost/rh/proj/virt/qemu/cpus.c:1743
> #18 0x0000559a4e83669a in qemu_thread_start (args=<optimized out>) at util/qemu-thread-posix.c:502
> #19 0x00007f2e4ebf958e in start_thread () at /lib64/libpthread.so.0
> #20 0x00007f2e4eb266f3 in clone () at /lib64/libc.so.6
> 
> 
> For reference, this is the QEMU command line:
> 
> aarch64-softmmu/qemu-system-aarch64 -chardev socket,id=mon,path=/var/tmp/tmpxnkcjvf0/qemu-6453-monitor.sock -mon chardev=mon,mode=control -display none -vga none -machine virt -chardev socket,id=console,path=/var/tmp/tmpxnkcjvf0/qemu-6453-console.sock,server,nowait -serial chardev:console -cpu cortex-a53 -kernel /home/ehabkost/rh/proj/virt/qemu/tests/venv/data/cache/by_location/e959d0e1dd72e77653e218e666198db1f3d0c213/vmlinuz -append printk.time=0 console=ttyAMA0
> 
> 
> 
> -- 
> Eduardo

Besides the command line, I hope it's also easy to use the following
reproducer:

 https://github.com/clebergnu/qemu/commit/c778e28c24030c4a36548b714293b319f4bf18df

It should apply cleanly to QEMU master, and instructions on how to run
it are documented in the commit message.

Thanks,
- Cleber.