On Thu, Aug 28, 2025, Rick P Edgecombe wrote: > On Thu, 2025-08-28 at 10:00 -0700, Sean Christopherson wrote: > > > tdx_td_finalize() now just returns -EINVAL in case of nr_premapped being !0. > > > KVM_BUG_ON/WARN_ON should be also ok. > > > > Ok, so I vaguely recall that I may have pushed back on using a scratch field in > > "struct kvm_tdx" for temporary data (or maybe it was abusing vcpus[0] that I > > disliked?), but what we ended up with is far worse. > > I think it was also that the tdh_mr_extend() loop was too heavyweight for the > fault path. But that was before we got to the kick+lock stuff. Me confused. This is pre-boot, not the normal fault path, i.e. blocking other operations is not a concern. If tdh_mr_extend() is too heavy for a non-preemptible section, then the current code is also broken in the sense that there are no cond_resched() calls. The vast majority of TDX hosts will be using non-preemptible kernels, so without an explicit cond_resched(), there's no practical difference between extending the measurement under mmu_lock versus outside of mmu_lock. _If_ we need/want to do tdh_mr_extend() outside of mmu_lock, we can and should still do tdh_mem_page_add() under mmu_lock.
