0b210faf33
Add a "never" option to the nx_huge_pages module param to allow userspace to do a one-way hard disabling of the mitigation, and don't create the per-VM recovery threads when the mitigation is hard disabled. Letting userspace pinky swear that userspace doesn't want to enable NX mitigation (without reloading KVM) allows certain use cases to avoid the latency problems associated with spawning a kthread for each VM. E.g. in FaaS use cases, the guest kernel is trusted and the host may create 100+ VMs per logical CPU, which can result in 100ms+ latencies when a burst of VMs is created. Reported-by: Li RongQing <lirongqing@baidu.com> Closes: https://lore.kernel.org/all/1679555884-32544-1-git-send-email-lirongqing@baidu.com Cc: Yong He <zhuangel570@gmail.com> Cc: Robert Hoo <robert.hoo.linux@gmail.com> Cc: Kai Huang <kai.huang@intel.com> Reviewed-by: Robert Hoo <robert.hoo.linux@gmail.com> Acked-by: Kai Huang <kai.huang@intel.com> Tested-by: Luiz Capitulino <luizcap@amazon.com> Reviewed-by: Li RongQing <lirongqing@baidu.com> Link: https://lore.kernel.org/r/20230602005859.784190-1-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>