[Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM

[Dr. David Alan Gilbert]

Interesting; I thought this was supposed to work.
I know we (RH) have some downstream patches for >1TB RAM, but the last I'd 
heard they weren't supposed to be necessary any more, except for compatibility 
with old versions.

It's probably worth checking the guest view fo the CPUs physical address bits 
and making sure it's no bigger than the host (phys-bits=n or 
host-phys-bits=true on the -cpu)
QEMU often defaults to 40 bits and things get confusing.

Note also you can do some 1TB+ tests on smaller machines as long as they
have a large enough address size on the host CPUs.  Tricks like adding
empty hot-plug DIMM slots leaving a 1TB hole can tickle some bugs.
Even adding 1TB of swap to your host and being careful with your guest
can work :-)

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1769053

Title:
  Cannot start a guest with more than 1TB of RAM

Status in QEMU:
  Incomplete
Status in qemu package in Ubuntu:
  Incomplete

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.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1769053/+subscriptions