On Tue, Aug 16, 2022 at 1:17 AM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > On Mon, Aug 15, 2022 at 04:01:01PM -0700, David Matlack wrote: > > Patch 1 deletes the module parameter tdp_mmu and forces KVM to always > > use the TDP MMU when TDP hardware support is enabled. The rest of the > > patches are related cleanups that follow (although the kvm_faultin_pfn() > > cleanups at the end are only tangentially related at best). > > > > The TDP MMU was introduced in 5.10 and has been enabled by default since > > 5.15. At this point there are no known functionality gaps between the > > TDP MMU and the shadow MMU, and the TDP MMU uses less memory and scales > > better with the number of vCPUs. In other words, there is no good reason > > to disable the TDP MMU. > > Then how are you going to test the shadow mmu code -- which I assume is > still relevant for the platforms that don't have this hardware support > you speak of? TDP hardware support can still be disabled with module parameters (kvm_intel.ept=N and kvm_amd.npt=N). The tdp_mmu module parameter only controls whether KVM uses the TDP MMU or shadow MMU *when TDP hardware is enabled*.
