• Lorenzo Brescia's avatar
    kvm: tracing: Fix unmatched kvm_entry and kvm_exit events · d95df951
    Lorenzo Brescia authored
    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: default avatarLorenzo Brescia <lorenzo.brescia@edu.unito.it>
    Signed-off-by: default avatarDario Faggioli <dfaggioli@suse.com>
    Message-Id: <160873470698.11652.13483635328769030605.stgit@Wayrath>
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    d95df951
vmx.c 222 KB