[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Looking at the comments here, I assume this has been a bug in the kernel, not in QEMU, so I'm closing this one now. If you still think this is something that needs fixing in QEMU, please open a new ticket in the new bug tracker at https://gitlab.com/qemu-project/qemu/-/issues instead. ** Changed in: qemu Status: Incomplete => Invalid -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: Invalid Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
The QEMU project is currently moving its bug tracking to another system. For this we need to know which bugs are still valid and which could be closed already. Thus we are setting the bug state to "Incomplete" now. If the bug has already been fixed in the latest upstream version of QEMU, then please close this ticket as "Fix released". If it is not fixed yet and you think that this bug report here is still valid, then you have two options: 1) If you already have an account on gitlab.com, please open a new ticket for this problem in our new tracker here: https://gitlab.com/qemu-project/qemu/-/issues and then close this ticket here on Launchpad (or let it expire auto- matically after 60 days). Please mention the URL of this bug ticket on Launchpad in the new ticket on GitLab. 2) If you don't have an account on gitlab.com and don't intend to get one, but still would like to keep this ticket opened, then please switch the state back to "New" or "Confirmed" within the next 60 days (other- wise it will get closed as "Expired"). We will then eventually migrate the ticket automatically to the new system (but you won't be the reporter of the bug in the new system and thus you won't get notified on changes anymore). Thank you and sorry for the inconvenience. ** Changed in: qemu Status: New => Incomplete -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: Incomplete Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Ran into the same issue on Proxmox 6.3-3 Setting `bcdedit /set xsavedisable 1` and using cpu=host works for me Without I get bootloops and other options that luqmana posted, Hyper-V fails to start -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Oh, and I guess I misinterpreted what -mpx was for. To be clear, I was running into 2 issues: 1. Hyper-V fails to initialize. "Fixed" by one of: a) using named cpu model b) cpu=host and running `bcdedit /set xsavedisable 1` in Windows before enabling Hyper-V c) cpu=host,-mpx d) my hack-y patch from earlier (b) just tells Hyper-V to disable XSAVE support for its (nested) guests altogether whereas (c) is more fine=grained and just disables the BNDCFGx bits. 2. Hyper-V initializes but Windows bootloops. I only seem to run into this with 5.8 but not 5.4 or 5.10. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
It's more likely to be a bug in KVM. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
I haven't tried 5.9, just: - 5.4.0-58 Works - 5.8.0-33 (20.04 HWE Edge)Bootloop - 5.10.1-051001Works If I have time later I can try narrowing down which kernel causes the issue. But is the BNDCFGS MSR issue considered a bug in qemu or what? -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
If you can bisect between 5.9 (I understand it's bad?) and 5.10 we could propose it for stable kernels. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Adding -mpx doesn't seem to help on 5.8, the guest still bootloops. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Aha! The final boot loop issue is resolved if I either upgrade to 5.10 or downgrade to 5.4 from 5.8. So the main issue then seems to be the missing control bits. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
Re: [Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Try instead disabling MPX with "-cpu host,-mpx". -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
** Bug watch added: bugs.centos.org/ #17788 https://bugs.centos.org/view.php?id=17788 ** Also affects: qemu-kvm (CentOS) via https://bugs.centos.org/view.php?id=17788 Importance: Unknown Status: Unknown -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Status in qemu-kvm package in CentOS: Unknown Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Ok, so I narrowed done one possible issue: the BNDCFGS bits in the vm entry/exit control MSRs are not set but HyperV expects them to be set if xsave is supported. This quick patch actually lets Hyper-V initialize and continue booting: https://gist.github.com/552baa8be026e67bef2d223076b81636 An alternative to that patch is just telling Hyper-V xsave is disabled. In the guest before enabling Hyper-V: bcdedit /set xsavedisable 1 Unfortunately while this does let the guest Hyper-V initialize, the nested (root) Windows guest doesn't boot and still gets stuck in a bootloop. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
Ok, after bisect between stable-4.1 and stable-4.2 I did confirm that https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 is the first bad commit. The full qemu command line is: qemu-system-x86_64 \ -name guest=test,debug-threads=on \ -serial none \ -enable-kvm \ -nodefaults \ -no-user-config \ -M q35,accel=kvm,kernel_irqchip=on,mem-merge=off \ -m 8192 -mem-prealloc -no-hpet \ -cpu host,kvm=off,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time \ -smp 8,sockets=1,cores=4,threads=2 \ -global kvm-pit.lost_tick_policy=discard \ -rtc base=localtime \ -boot order=c \ -usb \ -device pcie-root-port,bus=pcie.0,id=root_port1,chassis=0,slot=0 \ -device vfio-pci,host=01:00.0,id=hostdev1,bus=root_port1,addr=0x00,multifunction=on \ -device vfio-pci,host=01:00.1,id=hostdev2,bus=root_port1,addr=0x00.1 \ -drive if=pflash,format=raw,readonly,file=OVMF_CODE.fd \ -drive if=pflash,format=raw,file=OVMF_VARS.fd \ -drive if=none,id=drivec,file=disk.img,format=qcow2,cache=none,aio=threads \ -object iothread,id=iothread1 \ -device virtio-blk-pci,drive=drivec,scsi=off,iothread=iothread1 \ -monitor unix:/tmp/monitor.sock,server,nowait \ -device virtio-mouse-pci,id=input0 \ -device virtio-keyboard-pci,id=input1 \ -object input-linux,id=kbd1,evdev=/dev/input/by-id/xxx,grab_all=yes,repeat=on \ -object input-linux,id=mouse1,evdev=/dev/input/by-id/xx \ -netdev tap,ifname=vnet,id=net0,script=no,downscript=no \ -device e1000,netdev=net0 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
** Attachment added: "cpuinfo.txt" https://bugs.launchpad.net/qemu/+bug/1908489/+attachment/556/+files/cpuinfo.txt -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions
[Bug 1908489] Re: qemu 4.2 bootloops with -cpu host and nested hypervisor
** Attachment added: "vmxcap" https://bugs.launchpad.net/qemu/+bug/1908489/+attachment/555/+files/vmxcap.txt -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1908489 Title: qemu 4.2 bootloops with -cpu host and nested hypervisor Status in QEMU: New Bug description: I've noticed that after upgrading from Ubuntu 18.04 to 20.04 that nested virtualization isn't working anymore. I have a simple repro where I create a Windows 10 2004 guest and enable Hyper-V in it. This worked fine in 18.04 and specifically qemu <4.2 (I specifically tested Qemu 2.11-4.1 which work fine). The -cpu arg I'm passing is simply: -cpu host,l3-cache=on,hv_relaxed,hv_spinlocks=0x1fff,hv_vapic,hv_time Using that Windows won't boot because the nested hypervisor (Hyper-V) is unable to be initialize and so it just boot loops. Using the exact same qemu command works fine with 4.1 and lower. Switching to a named CPU model like Skylake-Client-noTSX-IBRS instead of host lets the VM boot but causes some weird behaviour later trying to use nested VMs. If I had to guess I think it would probably be related to this change https://github.com/qemu/qemu/commit/20a78b02d31534ae478779c2f2816c273601e869 which would line up with 4.2 being the first bad version but unsure. For now I just have to keep an older build of QEMU to work around this. Let me know if there's anything else needed. I can also try out any patches. I already have at least a dozen copies of qemu lying around now. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1908489/+subscriptions