[Qemu-devel] [Bug 1448985] Re: llvmpipe i386 crashes when running on qemu64 cpu

[Stefan Bader]

Since we no longer produce i386 images, this would be hard to reproduce.
I could imagine the issue still exists but nobody is or will care.
Essentially a difference of what features are reported via cpuid and
what actually is implemented in the cpu emulation. Will close at least
the Ubuntu side.

** Changed in: llvm-toolchain-3.6 (Ubuntu)
       Status: Incomplete => Won't Fix

** Changed in: qemu (Ubuntu)
       Status: Incomplete => Won't Fix

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https://bugs.launchpad.net/bugs/1448985

Title:
  llvmpipe i386 crashes when running on qemu64 cpu

Status in QEMU:
  Incomplete
Status in llvm-toolchain-3.6 package in Ubuntu:
  Won't Fix
Status in qemu package in Ubuntu:
  Won't Fix

Bug description:
  STEPS TO REPRODUCE:
     1. Install Ubuntu 14.04.2 LTS or Ubuntu 14.10 or Ubuntu 15.04 with all 
updates (it is a host system).
     2. Download one (or all) isos:
        * Ubuntu 14.0.4.2 i386 iso (ubuntu-14.04.2-desktop-i386.iso, MD5SUM = 
a8a14f1f92c1ef35dae4966a2ae1a264).
        * Ubuntu 14.10 i386 iso (ubuntu-14.10-desktop-i386.iso, MD5SUM = 
4a3c4b8421af51c29c84fb6f4b3fe109)
        * Ubuntu 15.04 i386 iso (ubuntu-15.04-desktop-i386.iso, MD5SUM = 
6ea04093b767ad6778aa245d53625612)
     3. Boot one (or all) isos with as QEMU-KVM guest with the following 
commands:
        * sudo kvm -m 1536 -cdrom ubuntu-*-desktop-i386.iso
        * sudo kvm -m 1536 -cdrom ubuntu-*-desktop-i386.iso -vga std
        * sudo kvm -m 1536 -cdrom ubuntu-*-desktop-i386.iso -vga vmware
        *  or from usb-creator-gtk via "Test disk" button
     4. Click on "Try Ubuntu"

  EXPECTED RESULTS:
      ISO is booted to Unity desktop, user can test and use it.

  ACTUAL RESULTS:
     In 14.04 and 14.10 guests can see empty purple desktop or purple desktop 
with two shortcuts ("Examples" and "Install Ubuntu ...").
     15.10 guest does not boot or boot to safe graphic mode (it is bug 1437740).

  The reason for this is that unity requires gfx acceleration which is
  done via llvmpipe on non accelerated gfx chipsets (as VMs use by
  default). The error message is hidden away but is:

  LLVM ERROR: Do not know how to split the result of this operator!

  The cause is that KVM VMs by default use the qemu64 cpu model which
  seems to be inconsistent in some way between claimed features and
  actual results when using those features. A work-around for running
  i386 isos is to use a cpu model like core2duo or kvm64.

  This bug should be confirmed and fixed.
  Users may want to run Ubuntu in QEMU/KVM, not just VirtualBox.

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