Messages in this thread | | | Date | Fri, 17 Apr 2020 12:11:59 -0700 | From | Sean Christopherson <> | Subject | Re: [PATCH 0/3] KVM: x86: move nested-related kvm_x86_ops to a separate struct |
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On Fri, Apr 17, 2020 at 03:05:53PM -0400, Peter Xu wrote: > On Fri, Apr 17, 2020 at 12:44:10PM -0400, Paolo Bonzini wrote: > > While this reintroduces some pointer chasing that was removed in > > afaf0b2f9b80 ("KVM: x86: Copy kvm_x86_ops by value to eliminate layer > > of indirection", 2020-03-31), the cost is small compared to retpolines > > and anyway most of the callbacks are not even remotely on a fastpath. > > In fact, only check_nested_events should be called during normal VM > > runtime. When static calls are merged into Linux my plan is to use them > > instead of callbacks, and that will finally make things fast again by > > removing the retpolines. > > Paolo, > > Just out of curiousity: is there an explicit reason to not copy the > whole kvm_x86_nested_ops but use pointers (since after all we just > reworked kvm_x86_ops)?
Ya, my vote would be to copy by value as well. I'd also be in favor of dropping the _ops part, e.g.
struct kvm_x86_ops { struct kvm_x86_nested_ops nested;
... };
and drop the "nested" parts from the ops, e.g.
check_nested_events() -> check_events()
which yields:
r = kvm_x86_ops.nested.check_events(vcpu); if (r != 0) return r;
I had this coded up but shelved it when svm.c got fractured :-).
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