On Wed, Sep 11, 2024, Nikolas Wipper wrote: > On Wed Sep 11, 2024 at 04:36 PM UTC+0200, Sean Christopherson wrote: > > On Wed, Sep 11, 2024, Nikolas Wipper wrote: > >> Having this API, and specifically having a definite kvm_one_reg structure > >> for x86 registers, would be interesting for register pinning/intercepts. > >> With one_reg for x86 the API could be platform agnostic and possible even > >> replace MSR filters for x86. > > > > I don't follow. MSR filters let userspace intercept accesses for a variety of > > reasons, these APIs simply provide a way to read/write a register value that is > > stored in KVM. I don't see how this could replace MSR filters. > > Nope, that would be an entirely different API, but if that uses one reg IDs it > could be unified to cover CRs and MSRs all in one. Oooh, gotcha. Yeah, uniquely identifiable registers would allow for a generic filtering API, though I'm not entirely sure that's actually a good idea in the long run. Most x86 registers can't be intercepted; having a generic filtering API might incur an annoyingly high maintenance cost. Hmm, though it should be easy enough to explicitly allow only MSR and CR types, so if/when we get to the point where CR pinning/filtering is desirable/ready, then a unified API probably does make sense.
