Register KVM's cpuhp and syscore callbacks when enabling virtualization in hardware, as the sole purpose of said callbacks is to disable and re-enable virtualization as needed. The primary motivation for this series is to simplify dealing with enabling virtualization for Intel's TDX, which needs to enable virtualization when kvm-intel.ko is loaded, i.e. long before the first VM is created. TDX doesn't _need_ to keep virtualization enabled, but doing so is much simpler for KVM (see patch 3). That said, this is a nice cleanup on its own, assuming I haven't broken something. By registering the callbacks on-demand, the callbacks themselves don't need to check kvm_usage_count, because their very existence implies a non-zero count. The meat is in patch 1. Patches 2 renames the helpers so that patch 3 is less awkward. Patch 3 adds a module param to enable virtualization when KVM is loaded. Patches 4-6 are tangentially related x86 cleanups to registers KVM's "emergency disable" callback on-demand, same as the syscore callbacks. Moderately well tested on x86, though I haven't (yet) done due dilegence on the suspend/resume and cphup paths. Compile tested on other architectures, but that's all for this version. v2: - Use a dedicated mutex to avoid lock inversion issues between kvm_lock and the cpuhp lock. - Register emergency disable callbacks on-demand. [Kai] - Drop an unintended s/junk/ign rename. [Kai] - Decrement kvm_usage_count on failure. [Chao] v1: https://lore.kernel.org/all/20240425233951.3344485-1-seanjc@xxxxxxxxxx Sean Christopherson (6): KVM: Register cpuhp and syscore callbacks when enabling hardware KVM: Rename functions related to enabling virtualization hardware KVM: Add a module param to allow enabling virtualization when KVM is loaded KVM: Add arch hooks for enabling/disabling virtualization x86/reboot: Unconditionally define cpu_emergency_virt_cb typedef KVM: x86: Register "emergency disable" callbacks when virt is enabled arch/x86/include/asm/kvm_host.h | 3 + arch/x86/include/asm/reboot.h | 2 +- arch/x86/kvm/svm/svm.c | 5 +- arch/x86/kvm/vmx/main.c | 2 + arch/x86/kvm/vmx/vmx.c | 6 +- arch/x86/kvm/vmx/x86_ops.h | 1 + arch/x86/kvm/x86.c | 10 ++ include/linux/kvm_host.h | 2 + virt/kvm/kvm_main.c | 258 ++++++++++++++++---------------- 9 files changed, 150 insertions(+), 139 deletions(-) base-commit: 4aad0b1893a141f114ba40ed509066f3c9bc24b0 -- 2.45.0.215.g3402c0e53f-goog
