[Bug 1888303] [NEW] Intermittent buggines with user mode emulation of x86-64 on aarch64

From: Gordan Bobic <1888303@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1888303] [NEW] Intermittent buggines with user mode emulation of x86-64 on aarch64
Date: Mon, 20 Jul 2020 19:18:37 -0000	[thread overview]
Message-ID: <159527271737.12536.2281351511750409436.malonedeb@gac.canonical.com> (raw)

Public bug reported:

QEMU Version: 5.0.0
./configure --target-list=x86_64-linux-user --enable-user --prefix=/opt/qemu --static

Testing using node_exporter from pmm-client-1.17.4-1.el8.x86_64.rpm

aarch64 system is running CentOS 8 with a mainline 5.4.52 kernel built
for 4KB memory pages.

On aarch64 machine, invoke:

./qemu-x86_64-static /usr/local/percona/pmm-client/node_exporter.x86_64
-web.listen-address=192.168.0.10:42000 -web.auth-file=/usr/local/percona
/pmm-client/pmm.yml -web.ssl-key-file=/usr/local/percona/pmm-
client/server.key -web.ssl-cert-file=/usr/local/percona/pmm-
client/server.crt
-collectors.enabled=diskstats,filefd,filesystem,loadavg,meminfo,netdev,netstat,stat,time,uname,vmstat,meminfo_numa,textfile

Most of the time it will outright segfault within a few seconds,
seemingly when the prometheus server polls for data.

But, about once every 10 times, it will not sefault and will continue
working just fine forever.

The dynamically linked version of qemu (built without --static) always
works without segfaulting, but it just doesn't work, the prometheus
server gets no data from it. Again, once in a while it will work, but
even when it doesn't work it won't segfault.

This vaguely feels like a memory alignment issue somewhere, but my
debug-fu is not quite strong enough to attack the problem.

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1888303

Title:
  Intermittent buggines with user mode emulation of x86-64 on aarch64

Status in QEMU:
  New

Bug description:
  QEMU Version: 5.0.0
  ./configure --target-list=x86_64-linux-user --enable-user --prefix=/opt/qemu --static

  Testing using node_exporter from pmm-client-1.17.4-1.el8.x86_64.rpm

  aarch64 system is running CentOS 8 with a mainline 5.4.52 kernel built
  for 4KB memory pages.

  On aarch64 machine, invoke:

  ./qemu-x86_64-static /usr/local/percona/pmm-
  client/node_exporter.x86_64 -web.listen-address=192.168.0.10:42000
  -web.auth-file=/usr/local/percona/pmm-client/pmm.yml -web.ssl-key-
  file=/usr/local/percona/pmm-client/server.key -web.ssl-cert-
  file=/usr/local/percona/pmm-client/server.crt
  -collectors.enabled=diskstats,filefd,filesystem,loadavg,meminfo,netdev,netstat,stat,time,uname,vmstat,meminfo_numa,textfile

  Most of the time it will outright segfault within a few seconds,
  seemingly when the prometheus server polls for data.

  But, about once every 10 times, it will not sefault and will continue
  working just fine forever.

  The dynamically linked version of qemu (built without --static) always
  works without segfaulting, but it just doesn't work, the prometheus
  server gets no data from it. Again, once in a while it will work, but
  even when it doesn't work it won't segfault.

  This vaguely feels like a memory alignment issue somewhere, but my
  debug-fu is not quite strong enough to attack the problem.

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