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

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Daniel Berrange (1769053@bugs.launchpad.net) wrote:
> Hmm, if we know that QEMU guests will crash & burn when > 1 TB mem, when
> host-phys-bits/phys-bits are unset, then perhaps libvirt should do the
> right thing by default here. eg we can't use host-phys-bits=true due to
> migration compat issues, but if we see > 1TB mem, libvirt could
> reasonably set phys-bits=NNN for some suitable value of NNN.  We should
> expose this in the XML config for the CPU explicitly too.

Yep:
  a) It should be possible to 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
  c) libvirt can check that if RAM > 2^phys-bits it can complain

but

  d) For smaller amount of RAM it might still fail if
RAM+rounding+pci+hotplug space goes over the limit.
     Figuring that limit out is tricky (and I thought it
     might be BIOS/EFI dependent as well depending where they
     decide to put their PCI devices)

Dave

> -- 
> You received this bug notification because you are subscribed to the bug
> report.
> 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
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

-- 
You received this bug notification because you are a member of qemu-
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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.

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