* ChristianEhrhardt (1769...@bugs.launchpad.net) wrote: > > Interesting; I thought this was supposed to work. > > Exactly that was my thought when triaging it initially > Furthermore I assume people working la57 (https://lwn.net/Articles/730925/) > and such ran tests on much bigger sizes.
I assume so, but I've not looked at the detail of that. > > Ah right Dan, if you're seeing the 40 bits physical in the guest you > definitely need to try the flags I suggest in comment 6; host-phys- > bits=true should work for you. > > I tested Bionic to be at least on libvirt 4.0 / qemu 2.11.1 when we want > to check things under the "supposed to work now" flag. > > Defaults: > Host: address sizes : 46 bits physical, 48 bits virtual > Guest: address sizes : 40 bits physical, 48 bits virtual > > I ensured that with option -cpu host,host-phys-bits=true set I successfully > get what my host can provide in the guest: > Guest: address sizes : 46 bits physical, 48 bits virtual > > Starting a guest with that >1TB (that would be mostly on swap if needed) > works just fine as expected. Here ~1063 GB from /proc/meminfo > MemTotal: 1114676492 kB OK, good - that suggests there's nothing missing. We enable host-phys-bits=true by default I think (in our machine type?) > I also checked a more compatible approach like -cpu qemu64,phys-bits=42 > and that works as well. > > IMHO - if anything - one could argue that libvirt/qemu could be smarter > about e.g. auto adding those arguments (or print a warning) when > crossing a certain memory size. The problem is there are a whole bunch of things that are hard to deal with: a) Cheaper CPUs tend to have smaller phys-bits even in the same generation; e.g. my laptop is still 36 bits, a lot are 39 bits. I think the same is true of the Xeon E3-.... family. It makes it hard to know what to pick when you're going to allow migration. b) Reasoning about the total address size range is difficult; you've got to take into account PCI address space and hot plug space etc to know where the upper edge is. Dave > So for now I'd stick to the "actually works" summary and keep the status > to incomplete. > > -- > 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 / dgilb...@redhat.com / 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
