kvm: tracing: Fix unmatched kvm_entry and kvm_exit events

On VMX, if we exit and then re-enter immediately without leaving
the vmx_vcpu_run() function, the kvm_entry event is not logged.
That means we will see one (or more) kvm_exit, without its (their)
corresponding kvm_entry, as shown here:

 CPU-1979 [002] 89.871187: kvm_entry: vcpu 1
 CPU-1979 [002] 89.871218: kvm_exit:  reason MSR_WRITE
 CPU-1979 [002] 89.871259: kvm_exit:  reason MSR_WRITE

It also seems possible for a kvm_entry event to be logged, but then
we leave vmx_vcpu_run() right away (if vmx->emulation_required is
true). In this case, we will have a spurious kvm_entry event in the
trace.

Fix these situations by moving trace_kvm_entry() inside vmx_vcpu_run()
(where trace_kvm_exit() already is).

A trace obtained with this patch applied looks like this:

 CPU-14295 [000] 8388.395387: kvm_entry: vcpu 0
 CPU-14295 [000] 8388.395392: kvm_exit:  reason MSR_WRITE
 CPU-14295 [000] 8388.395393: kvm_entry: vcpu 0
 CPU-14295 [000] 8388.395503: kvm_exit:  reason EXTERNAL_INTERRUPT

Of course, not calling trace_kvm_entry() in common x86 code any
longer means that we need to adjust the SVM side of things too.

Signed-off-by: Lorenzo Brescia <lorenzo.brescia@edu.unito.it>
Signed-off-by: Dario Faggioli <dfaggioli@suse.com>
Message-Id: <160873470698.11652.13483635328769030605.stgit@Wayrath>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>