** Description changed:
+ SRU Justification:
+ Impact: A KVM guest running a v3.3+ kernel will fail to load the kvm_intel
module when running on a v3.2 host. This is because the newer kernel module
will check for the presence of a CPU specific flag (which any real CPU would
have) in the MSRs that get passed to the guest. But older kernels would not set
it in the nested case.
+
+ Fix: Just add the required flag to the MSRs passed to guests. This
+ change is picked from the patch that enabled the feature but does not
+ enable anything beyond. It has been reviewed upstream and sent to
+ upstream stable.
+
+ Testcase: KVM host (Intel CPU) running Precise (3.2). Quantal KVM guest
+ will not be able to modprobe kvm-intel (while a Precise guest can). With
+ this change, the Quantal guest, too can load the module. Successfully
+ installed another Quantal guest in the L1 guest. Running "perf test" in
+ the Quantal guest will fail the RDPMC test as unsupported.
+
+ ---
+
12.04 LTS supports nested virtualization. If I use a 12.04 LTS kernel
with kvm_intel nested=1 (the default on 12.04 LS) and boot a 12.04 LTS
guest, I am able to load the kvm_intel kernel module in the guest. If I
use the same host and boot a 12.10 guest, the kvm_intel module does not
load:
$ sudo modprobe kvm_intel
FATAL: Error inserting kvm_intel
(/lib/modules/3.5.0-6-generic/kernel/arch/x86/kvm/kvm-intel.ko): Input/output
error
The kvm module loads fine in the guest. The guest is up to date 12.10
amd64. The host is up to date 12.04 LTS amd64 using an Intel i7 CPU.
** Also affects: linux (Ubuntu Precise)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu)
Status: Confirmed => Won't Fix
** Changed in: linux (Ubuntu Precise)
Status: New => In Progress
** Changed in: linux (Ubuntu Precise)
Importance: Undecided => High
** Changed in: linux (Ubuntu Precise)
Assignee: (unassigned) => Stefan Bader (stefan-bader-canonical)
** Changed in: linux (Ubuntu)
Assignee: Stefan Bader (stefan-bader-canonical) => (unassigned)
--
You received this bug notification because you are a member of Ubuntu
Bugs, which is subscribed to Ubuntu.
https://bugs.launchpad.net/bugs/1031090
Title:
kvm_intel not loadable in a quantal guest
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1031090/+subscriptions
--
ubuntu-bugs mailing list
[email protected]
https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
