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Diffstat (limited to 'gitlab/issues/target_missing/host_missing/accel_WHPX/2461.toml')
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1 files changed, 0 insertions, 64 deletions
diff --git a/gitlab/issues/target_missing/host_missing/accel_WHPX/2461.toml b/gitlab/issues/target_missing/host_missing/accel_WHPX/2461.toml deleted file mode 100644 index 72c10de3a..000000000 --- a/gitlab/issues/target_missing/host_missing/accel_WHPX/2461.toml +++ /dev/null @@ -1,64 +0,0 @@ -id = 2461 -title = "Qemu with -accel whpx doesn't set WRMSR permissions, which blocks nested virtualization" -state = "opened" -created_at = "2024-07-26T17:41:16.874Z" -closed_at = "n/a" -labels = ["accel: WHPX"] -url = "https://gitlab.com/qemu-project/qemu/-/issues/2461" -host-os = "Windows 11 23H2 Home" -host-arch = "x86_64" -qemu-version = "v9.0.0-12054-g923cf646f4" -guest-os = "Ubuntu 22.04" -guest-arch = "x86_64" -description = """This bug blocks https://gitlab.com/qemu-project/qemu/-/issues/628 - -Qemu doesn't set the host's Hyper-V permissions for WRMSR command to allow using SVM or VMX. Unset permissions lead to `unchecked MSR access error: WRMSR to 0xc0000080` inside Linux VM when trying to launch nested VM on real AMD cpu. Intel users do not see guest VMX feature at all. Please see **Additional info** section to understand how Hyper-V permissions for nested virtualization work in Windows.""" -reproduce = """1. Turn on VT-x (for Intel) or AMD-V virtualization in your real hardware BIOS/EFI. This was tested only on AMD cpu and Qemu 9, Intel \\*may\\* behave differently. - 2. Install any distro in qemu disk c:\\\\linux_disk.qcow2 with MSR enabled in kernel, for example, Ubuntu 22.04 LTS. - 3. Run qemu using `qemu-system-x86_64.exe -m 2048 -machine q35 -accel whpx -cpu Opteron_G5,check,+svm -hda c:\\linux_disk.qcow2` - - To check if your distro has MSR mod enabled, run `grep -i msr /boot/config-$(uname -r)` and it should return `CONFIG_X86_MSR=m` or `CONFIG_X86_MSR=y`. If not, recompile and reinstall your kernel. - 4. Run `sudo modprobe msr` and then `sudo rdmsr 0xc0000080 #EFER`. You should see `d01` on modern AMD models. \\[Untested\\] For intel, run `sudo modprobe msr`, then `sudo rdmsr 0x3A`. You should see `5` or `0x5` or `0x100005`. d01 for AMD and 5 for Intel in output are necessary to enable nested VM. If RDMSR returns non-zero value, it means that qemu developers implemented this part of functionality and your Hyper-V on Windows is not broken. - 5. Run `cat /proc/cpuinfo | grep -c svm` on AMD cpu, which should output a positive digit. - 6. Run `sudo dmesg | grep kvm` and note: - - `[1.924036] kvm_amd: Nested Virtualization enabled` - - `[1.924038] kvm_amd: Nested Paging disabled`\\ - `[1.924040] kvm_amd: PMU virtualization is disabled` - 7. This, in theory, is sufficient for KVM-acclelerated qemu to start a nested VM. - 8. Run `xhost si:localuser:root` to prevent `gtk initialization failed` error - 9. Run `sudo qemu-system-x86_64 -accel kvm`. A black window with "Guest has not initialized the display (yet)." appears. -10. Run `sudo dmesg` and note qemu crash starting with `unchecked MSR access error: WRMSR` - - \\* Steps 1-4 are only required for diagnostics, and KVM works (in native Windows Hyper-V manager) without the necessarity to enter these commands in usual usage scenarios. If you run <span dir="">`cat /proc/cpuinfo | grep -c vmx` on Intel cpu</span> on Step 5, you may get zero. See Step 5 of Additional Info to understand why. - - \\ - Microsoft released useful info about how to look into Hyper-V MSR access problems:\\ - WRMSR research in Hyper-V - https://msrc.microsoft.com/blog/2018/12/first-steps-in-hyper-v-research/""" -additional = """By default, Hyper-V manager in Windows does not allow nested virtualization.\\ -To see what happens, do the following: - - 1. Open Hyper-V manager built in the host Windows and create default Ubuntu 22.04 LTS suggested. Upon installation, shut down the VM. Note the name of the VM ("Ubuntu 22.04 LTS" by default). - 2. Open Powershell console in the host and run `Set-VMProcessor -VMName "Ubuntu 22.04 LTS" -ExposeVirtualizationExtensions $false` - 3. Launch guest Ubuntu 22.04 LTS, open its terminal and run `sudo dmesg | grep kvm`. No output. - 4. Run `sudo rdmsr 0xc0000080 #EFER` that outputs d01, which means that Hyper-V manager allows this **ring 0 level** operation. - 5. Run `cat /proc/cpuinfo | grep -c svm` for AMD or `cat /proc/cpuinfo | grep -c vmx` for Intel. Note that output is `0`. - 6. Shut the VM down. - 7. Now, Open Powershell console and `run Set-VMProcessor -VMName "Ubuntu 22.04 LTS" -ExposeVirtualizationExtensions $true` - 8. Launch Ubuntu 22.04 LTS, open its terminal and run `sudo dmesg | grep kvm`. Output: - - `[2.369144] kvm: Nested Virtualization enabled` - - `[2.369146] SVM: kvm: Nested Paging enabled` - - `[2.369148] SVM: kvm: Hyper-V enlightened NPT TLB flush enabled` - - `[2.369149] SVM: kvm: Hyper-V Direct TLB flush enabled` - - `[2.369153] SVM: Virtual VMLOAD VMSAVE supported` - 9. Run `cat /proc/cpuinfo | grep -c svm` for AMD or `cat /proc/cpuinfo | grep -c vmx` for Intel. Note that output is `1` or other positive digit, depending on the number of cpus you've assigned to the VM. -10. Run `xhost si:localuser:root` to prevent `gtk initialization failed` error -11. Run `sudo qemu-system-x86_64 -accel kvm` and it successfully boots into qemu BIOS. -12. Running `sudo qemu-system-x86_64 -accel kvm` calls WRMSR in background, so if you see\\ - booted qemu BIOS in KVM, wrmsr was successfully called.""" |