[Qemu-devel] [Bug 1769053] Re: Ability to control phys-bits through libvirt

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On 2018-05-15T07:41:18+00:00 paelzer wrote:

Description of problem:
Based on a discussion about Qemus ability to work with Guests >1TB [1] it was 
identified that it might be wise to have libvirt be able to:
  a) add a setting to the XML to specify the phys-bits
  b) It should be possible for libvirt to check the host it's on can
     satisfy that requirement (enough HW phys bits)
  c) libvirt can check that if RAM > 2^phys-bits it can complain

It is known that (c) can't catch all, as it might still fail if
RAM+rounding+pci+hotplug space goes over the limit. Figuring that limit
out is tricky and should not be part of the scope here.

[1]: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1769053

Version-Release number of selected component (if applicable):
Up to latest 4.3

How reproducible:
100% - well it essentially is a feature request not an error

Steps to Reproduce:
1. try to control phys-bits through libvirt xml/api

Actual results:
No option exposed to do so.

Expected results:
Be able to control phys-bits

Additional info:
See the discussion on Launchpad [1] for more details of the qemu side of this.

Reply at:
https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1769053/comments/21


** Changed in: libvirt
       Status: Unknown => Confirmed

** Changed in: libvirt
   Importance: Unknown => Undecided

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https://bugs.launchpad.net/bugs/1769053

Title:
  Ability to control phys-bits through libvirt

Status in libvirt:
  Confirmed
Status in QEMU:
  Invalid
Status in libvirt package in Ubuntu:
  Triaged
Status in qemu package in Ubuntu:
  Invalid

Bug description:
  Attempting to start a KVM guest with more than 1TB of RAM fails.

  It looks like we might need some extra patches:
  https://lists.gnu.org/archive/html/qemu-discuss/2017-12/msg00005.html

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: qemu-system-x86 1:2.11+dfsg-1ubuntu7
  ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
  Uname: Linux 4.15.0-20-generic x86_64
  ApportVersion: 2.20.9-0ubuntu7
  Architecture: amd64
  CurrentDesktop: Unity:Unity7:ubuntu
  Date: Fri May  4 16:21:14 2018
  InstallationDate: Installed on 2017-04-05 (393 days ago)
  InstallationMedia: Ubuntu 16.10 "Yakkety Yak" - Release amd64 (20161012.2)
  MachineType: Dell Inc. XPS 13 9360
  ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.15.0-20-generic 
root=/dev/mapper/ubuntu--vg-root ro quiet splash transparent_hugepage=madvise 
vt.handoff=1
  SourcePackage: qemu
  UpgradeStatus: Upgraded to bionic on 2018-04-30 (3 days ago)
  dmi.bios.date: 02/26/2018
  dmi.bios.vendor: Dell Inc.
  dmi.bios.version: 2.6.2
  dmi.board.name: 0PF86Y
  dmi.board.vendor: Dell Inc.
  dmi.board.version: A00
  dmi.chassis.type: 9
  dmi.chassis.vendor: Dell Inc.
  dmi.modalias: 
dmi:bvnDellInc.:bvr2.6.2:bd02/26/2018:svnDellInc.:pnXPS139360:pvr:rvnDellInc.:rn0PF86Y:rvrA00:cvnDellInc.:ct9:cvr:
  dmi.product.family: XPS
  dmi.product.name: XPS 13 9360
  dmi.sys.vendor: Dell Inc.

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