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[Launchpad Bug Tracker <1807743@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package qemu - 1:2.5+dfsg-5ubuntu10.34

---------------
qemu (1:2.5+dfsg-5ubuntu10.34) xenial; urgency=medium

  * d/p/ubuntu/lp1807743-linux-user-timerfd.patch: fix define for
    timerfd_create system call (LP: #1807743)

 -- Christian Ehrhardt <christian.ehrhardt@xxxxxxxxxxxxx>  Wed, 12 Dec
2018 13:18:01 +0100

** Changed in: qemu (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1807743

Title:
  QEMU timerfd_create support on PowerPC

Status in qemu package in Ubuntu:
  Fix Released
Status in qemu source package in Precise:
  Invalid
Status in qemu source package in Trusty:
  Invalid
Status in qemu source package in Xenial:
  Fix Released
Status in qemu source package in Bionic:
  Fix Released
Status in qemu source package in Cosmic:
  Fix Released

Bug description:
  [Impact]

   * A bad named define made timerfd_create be in the code but not
  available

   * two smaller fixes to be backported from upstream that change the define
     names; This will enable the timerfd_create in qemu-user

  [Test Case]

   * Compile the attached source code using your host C compiler.
     => https://launchpadlibrarian.net/401131808/timerfd_support_test.c
      $ apt install build-essential
      $ gcc -Wall timertest.c -o timertest
   * Run the resulting binary.
     It should run for 3 seconds and print timer information. (sanity 
     test)
      $ ./timertest
   * Compile the attached source code using a PowerPC cross compiler with
     static linking enabled (to make the remaining steps simpler).
       $ apt install gcc-powerpc64-linux-gnu
       $ powerpc64-linux-gnu-gcc -static -Wall timertest.c -o timertest
   * Run the resulting binary using the unpatched qemu-user or qemu-user-
     static executable for your selected PowerPC architecture. It should 
     exit immediately complaining about an unsupported syscall.
       $ apt install qemu-user
       $ qemu-ppc64 ./timertest
         qemu: Unsupported syscall: 306
         timerfd_create(CLOCK_REALTIME): Function not implemented

   * Run the same binary using the patched qemu-user or qemu-user-static
     executable for your selected PowerPC architecture.
     It should behave as the host version did.

  Note: If you chose a big-endian PowerPC architecture, the "timer
  expirations" output may be "72057594037927936" instead of "1" because
  the bytes read were in host byte order instead of target byte order.

  [Regression Potential]

   * The headers are only used internally so no outside regression should
     happen.
   * Even then only the names changed but the number stayed, that means even
     if it would be an external ABI (it isn't) the number would be the same
   * Internally the old define was only used when defining it, but not used
     (see grep in comment #1)
   * The one regression I could think of is software running in qemu-user
     today and working by having a path like "does this have timerfd create
     -> no, ok then do A", with the change this might become "-> yes, so do
     B" and if that B is broken there would be a regression, but I'd
     consider it unlikely since all versions after Xenials 2.5 had the new
     variant and I have seen no complaints about it.

  [Other Info]

   * n/a

  ---

  QEMU erroneously fails to detect support for the timerfd_create
  syscall when running user-mode emulation of PowerPC targets. QEMU
  supports the timerfd_create syscall, but because the PowerPC target
  syscall header has it named "timerfd" instead of "timerfd_create",
  support is erroneously not enabled. This notably affects anything that
  uses Boost.Asio with deadline timers because it uses timerfds under
  the hood. I have attached a patch to fix the problem. For now I have a
  custom-built qemu-user-static.deb file with this fix implemented, but
  I would appreciate it if you could officially backport this patch to
  16.04 LTS (Xenial) so our developers can use the official package
  repositories.

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