On Mon, Aug 04, 2025, dan.j.williams@xxxxxxxxx wrote: > Xu Yilun wrote: > > So my idea is to remove tdx_tsm device (thus disables tdx_tsm driver) on > > vmxoff. > > > > KVM TDX core TDX TSM driver > > ----------------------------------------------------- > > tdx_disable() > > tdx_tsm dev del > > driver.remove() > > vmxoff() > > > > An alternative is to move vmxon/off management out of KVM, that requires > > a lot of complex work IMHO, Chao & I both prefer not to touch it. Eh, it's complex, but not _that_ complex. > It is fine to require that vmxon/off management remain within KVM, and > tie the lifetime of the device to the lifetime of the kvm_intel module*. Nah, let's do this right. Speaking from experience; horrible, make-your-eyes-bleed experience; playing games with kvm-intel.ko to try to get and keep CPUs post-VMXON will end in tears. And it's not just TDX-feature-of-the-day that needs VMXON to be handled outside of KVM, I'd also like to do so to allow out-of-tree hypervisors to do the "right thing"[*]. Not because I care deeply about out-of-tree hypervisors, but because the lack of proper infrastructure for utilizing virtualization hardware irks me. The basic gist is to extract system-wide resources out of KVM and into a separate module, so that e.g. tdx_tsm or whatever can take a dependency on _that_ module and elevate refcounts as needed. All things considered, there aren't so many system-wide resources that it's an insurmountable task. I can provide some rough patches to kickstart things. It'll probably take me a few weeks to extract them from an old internal branch, and I can't promise they'll compile. But they should be good enough to serve as an RFC. https://lore.kernel.org/all/ZwQjUSOle6sWARsr@xxxxxxxxxx > * It would be unfortunate if userspace needed to manually probe for TDX > Connect when KVM is not built-in. We might add a simple module that > requests kvm_intel in that case: Oh hell no :-) We have internal code that "requests" vendor module, and it might just be my least favorite thing. Juggling the locks and module lifetimes is just /shudder.
