I wouldn't call myself much of an expert on nested, but... On Wed, 2024-04-10 at 15:07 -0700, isaku.yamahata@xxxxxxxxx wrote: > There are several options to populate L1 GPA irrelevant to vCPU mode. > - Switch vCPU MMU only: This patch. > Pros: Concise implementation. > Cons: Heavily dependent on the KVM MMU implementation. Is switching just the MMU enough here? Won't the MTRRs and other vcpu bits be wrong? > - Use kvm_x86_nested_ops.get/set_state() to switch to/from guest mode. > Use __get/set_sregs2() to switch to/from SMM mode. > Pros: straightforward. > Cons: This may cause unintended side effects. Cons make sense. > - Refactor KVM page fault handler not to pass vCPU. Pass around necessary > parameters and struct kvm. > Pros: The end result will have clearly no side effects. > Cons: This will require big refactoring. But doesn't the fault handler need the vCPU state? > - Return error on guest mode or SMM mode: Without this patch. > Pros: No additional patch. > Cons: Difficult to use. Hmm... For the non-TDX use cases this is just an optimization, right? For TDX there shouldn't be an issue. If so, maybe this last one is not so horrible.
