#504 Nested kvm (SVM)
I have seen a couple messages where people have stated that nested SVM works properly, but I cannot replicate it. I first attempted to use the following configurations:
Hardware:
desktop system: Gigabyte MA785GM board with Athlon X2 4400
server system: Tyan h2000M board with Opteron 2354
Software:
Host OS: Ubuntu 9.10 with production kernel
Host KVM: tried kmod 2.6.32 with qemu 0.11.1 and qemu 0.12.0rc2, also tried git-tip
Guest VMM Host OS: Ubuntu 9.10
Guest VMM KVM: tried kmod 2.6.32 with qemu 0.11.1 and qemu 0.12.0rc2, also tried git-tip
True guest: tried Slackware 10.2, 64-bit Ubuntu 8.10, 64-bit Ubuntu 9.10, and 32-bit XP
All configurations result in the true guest not booting, but the Slackware 10.2 true guest is the easiest to analyze. It hangs at various places during boot with the most common being the "calibrating delay loop", "testing HLT instruction", mounting the hard disks, or starting the INIT processes. It seems it is losing interrupts.
I also tried an older host (64-bit Ubuntu 8.10) and guest VMM (64-bit Ubuntu 8.10) with the KVM-88 release. With this configuration, the Slackware 10.2 true guest will usually boot, but will then get a constant flow of "hda: lost interrupt" and "hda: dma_timer_expiry: dma status == 0x24". Again, it seems to be losing interrupts.
I have ensured that the nested=1 is passed to the module and that enable-nesting is passed to the qemu. It obviously works for some time and I've tried printing out exit reasons in the handle_exit() function of the guest VMM, but it consistently fails in some form or another across all the hardware and software I have to try it on.
Can you try disabling kvmclock in both guests?
I tried this again with qemu-0.12.2 and kvm-kmod-2.6.32.3 while passing no-kvmclock to both the host and guest VMM kernels. It did not help the problem of lost interrupts in the true guest, however.
Try reverting cd3ff653ae0b45bac7a19208e9c75034fcacc85f from kvm-kmod (kvm-svm). I ran into trouble with nested kvm about a month ago and bisected it back to this change. I alerted Joerg, but he might need another poke if this fixes nesting for you too.
Did this issue get resolved? Can we close the bug, there hasn't been any updates for over 9 months?