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charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/27/26 07:18, Chao Gao wrote: > We then switched to the guest-only approach to avoid allocating CET_KERNEL > space in non-KVM fpstates. The optimization could still be applied on top > of that, but it was dropped after its benefit was questioned off-list: > > """ > 1. It hacks in an optimization with conditionals around the edges, > instead of integrating with the way the rest of the FPU works. > 2. There is no proven benefit of this narrow optimization and x86 > maintainers are already skeptical. > """ > > This optimization can be added back if it benefits kernel shadow stacks. > But os_xrstor_supervisor() and os_xrstor_safe() would need the same > handling. That makes it more functional and less of an optimization. But, no less of a hack.