sim, kvm: make KvmVM a System parameter

Information
Submitter:	Curtis Dunham
Repository:	gem5
Branch:	default
Bugs:
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Description

A KVM VM is typically a child of the System object already, but for
solving future issues with configuration graph resolution, the most
logical way to keep track of this object is for it to be an actual
parameter of the System object.

Change-Id: I965ded22203ff8667db9ca02de0042ff1c772220
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

Testing Done

Is there any way you can remove the #if USE_KVM from the system.cc file? I don't have any suggestions off the top of my head, though.

Curtis Dunham Jan. 24, 2017, 6:22 a.m. (Jan. 24, 2017, 6:22 a.m.)

We agree that it's not the best, but we didn't see a better solution to this problem. We are willing to entertain suggestions, though.

Jason Lowe-Power Jan. 24, 2017, 7:22 a.m. (Jan. 24, 2017, 7:22 a.m.)

Yeah, sorry to ask for a change without any suggestions. I guess the real solution is to have cpu/kvm/vm.hh not dependent on linux/kvm.hh and include the KVM object in all compilations of gem5, whether or not KVM support is present on the host. This sounds like a major pain for a few #if's though.

Ship It!

src/sim/system.cc (Diff revision 1)

It seems we don't need #if here, p->kvm_vm will be nullptr in case there is no initialization from python. Right?

Curtis Dunham Jan. 26, 2017, 1:31 p.m. (Jan. 26, 2017, 1:31 p.m.)

System.py's kvm_vm parameter is conditional upon USE_KVM in the build environment, which is the same thing that conditionally adds all the KVM things to the build.  So in case KVM is not present, the KVM SimObject won't be a parameter of the System SimObject (error: 'System::Params {aka struct SystemParams' has no member named 'kvm_vm').

src/sim/system.cc (Diff revision 1)

Sorry, I should have been more specific. I meant by not conditioning System.kvm_vm by USE_KVM in System.py and have it be nullptr if KVM is not present we can get rid of some #if USE_KVM in the C++ code.

Curtis Dunham Jan. 30, 2017, 7:14 a.m. (Jan. 30, 2017, 7:14 a.m.)

When USE_KVM=0, nothing KVM-wise is built, so the Python declaration in System.py will fail, as there will be no KvmVM class.

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Status: Closed (submitted)