On 8/16/22 01:01, David Matlack wrote:
Delete the module parameter tdp_mmu and force KVM to always use the TDP MMU when TDP hardware support is enabled. 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. Dropping the ability to disable the TDP MMU reduces the number of possible configurations that need to be tested to validate KVM (i.e. no need to test with tdp_mmu=N), and simplifies the code.
The snag is that the shadow MMU is only supported on 64-bit systems; testing tdp_mmu=0 is not a full replacement for booting up a 32-bit distro, but it's easier (I do 32-bit testing only with nested virt). Personally I'd have no problem restricting KVM to x86-64 but I know people would complain.
What about making the tdp_mmu module parameter read-only, so that at least kvm->arch.tdp_mmu_enabled can be replaced by a global variable?
Paolo
