Bug 1475424 - Nested virtualization problem in kvm_amd with host-passthrough
Nested virtualization problem in kvm_amd with host-passthrough
Status: NEW
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
x86_64 Linux
unspecified Severity medium
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Assigned To: Kernel Maintainer List
Fedora Extras Quality Assurance
Depends On:
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Reported: 2017-07-26 12:08 EDT by Nandan Bhat
Modified: 2017-07-26 12:08 EDT (History)
7 users (show)

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Description Nandan Bhat 2017-07-26 12:08:18 EDT
Description of problem: Nested virtualization with kvm_amd does not work in Fedora 26. svm flag is not available in virtual machine while using host-passthrough mode for CPU

Version-Release number of selected component (if applicable): Kernels 4.11.8-300.fc26.x86_64 through 4.11.10-300.fc26.x86_64

How reproducible:
Every time

Steps to Reproduce: (In AMD FX-8320 system)
1. Install virtualization package group and restart (or start libvirtd).
2. Observe svm flag in /proc/cpuinfo and confirm /sys/modules/kvm_amd/parameters/nested to have 1 (even without enabling in /etc/modprobe.d/kvm.conf .
3. Create virtual machine with host-passthrough for CPU
3. Observe missing svm flag in /proc/cpuinfo in virtual machine.

Actual results:
Nested virtualization not working; only emulation available in virtual machine

Expected results:
(As functional in Fedora 25), nested virtualization works 

Additional info:
Fresh install of Fedora 25 on the same machine shows nested virtualization working fine. Fedora 26 x86_64 on Intel Core i5 based machine has functional nested virtualization.

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