It's a little unintuitive to see KVM_MSR_RET_FILTERED here, sinceActually KVM_MSR_RET_FILTERED seems more logical to use, especially in
userspace can make this happen on its own without having an entry in
this switch statement (by setting it in the msr filter bitmaps). When
using MSR filters, I would only expect to get MSR filter exits for
MSRs I specifically asked for.
Not a huge deal, just a little unintuitive. I'm not sure other options
are much better (you could put KVM_MSR_RET_INVALID, or you could just
not have these entries in svm_{get,set}_msr).
comparison with KVM_MSR_RET_INVALID.
Also, hooking this msr in svm_{get,set}_msr allows some in-kernel error
pre-processsing before doing the pass-through to userspace.