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Re: [Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM |
Date: |
Tue, 08 May 2018 14:00:19 -0000 |
* Gerd Hoffmann (address@hidden) wrote:
> Hi,
>
> > 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)
>
> Both seabios and ovmf try to not go too high in address space. Reason
> is exactly the phys-bits issue. Using 40 here by default does not only
> limit the memory to 1TB. It also has the problem that the guest thinks
> it has 1TB of address space but in reality it might be less. Even
> recent skylake machines have phys-bits=39 (512G) only, and trying to use
> the physical address space above 512G in the guest just doesn't work
> because the phys-bits=39 limit applies to EPT too.
>
> So checking phys-bits in the firmware, for example to place pci bars as
> high as possible in physical address space, is not going to work.
>
> IIRC ovmf uses a 32G sized region with 32G alignment by default, which
> will land below 64G (aka phys-bits=36 address space) unless the guest
> has more than 30 (q35) or 31 (piix4) GB of memory.
>
> seabios will not map pci bars above 4G unless it runs out of space below
> 4G. If needed 64bit PCI bars will be placed right above ram, with
> gigabyte alignment.
Yep, I was tempted to set host-phys-bits=true on upstream, but TCG
has a fixed 40 bits last time I looked.
Dave
> cheers,
> Gerd
>
> --
> 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 / address@hidden / Manchester, UK
--
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
[Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM, David Coronel, 2018/05/14
[Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM, Christian Ehrhardt , 2018/05/15
[Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM, Christian Ehrhardt , 2018/05/15
[Qemu-devel] [Bug 1769053] Re: Cannot start a guest with more than 1TB of RAM, Christian Ehrhardt , 2018/05/15