Paolo Bonzini <pbonz...@redhat.com> writes: > On 30/10/2018 12:26, Alexander Shishkin wrote: >> There is a control in the perf event attribute that enables tracing the >> guest. If this control is enabled, the kvm needs to stay away from any >> PT related MSRs. > > This cannot happen once the guest has been told it can trace itself.
So, they need to be made mutually exclusive. > There is no standard way to tell the guest that the host overrode its > choice to use PT. However, the host will get a PGD/PGE packet around > vmentry and vmexit, so there _will_ be an indication that the guest > owned the MSRs for that period of time. Not if they are not tracing the kernel. > If PT context switching is enabled with the module parameter, we could > also reject creation of events with the attribute set. However that > won't help if the event is created before KVM is even loaded. In that case, modprobe kvm should fail. Regards, -- Alex
