On 21. Aug 2019, at 23:34, Julien Grall > wrote: Hi Pawel, Hi Julien, On 8/21/19 9:19 AM, Pawel Wieczorkiewicz wrote: Livepatch only tracks an entire payload applied/reverted state. But, with an option to supply the apply_payload() and/or revert_payload() functions as optional hooks, it becomes possible to intermix the execution of the original apply_payload()/revert_payload() functions with their dynamically supplied counterparts. It is important then to track the current state of every function being patched and prevent situations of unintentional double-apply or unapplied revert. To support that, it is necessary to extend public interface of the livepatch. The struct livepatch_func gets additional field holding the applied/reverted state marker. To reflect the livepatch payload ABI change, bump the version flag LIVEPATCH_PAYLOAD_VERSION up to 2. The above solution only applies to x86 architecture for now. Is this going to break livepatch on Arm? If so, do you have any plan to fix it? No, I do not think it is. But, I am unable to test on Arm (No access to HW and SW), so I took the conservative approach here. [...] diff --git a/xen/include/xen/livepatch.h b/xen/include/xen/livepatch.h index 2aec532ee2..a93126f631 100644 --- a/xen/include/xen/livepatch.h +++ b/xen/include/xen/livepatch.h @@ -117,7 +117,7 @@ int arch_livepatch_quiesce(void); void arch_livepatch_revive(void); void arch_livepatch_apply(struct livepatch_func *func); -void arch_livepatch_revert(const struct livepatch_func *func); +void arch_livepatch_revert(struct livepatch_func *func); I doubt livepatch on Arm will compile after this change. What would be you suggestion then? Shall I limit the change to X86 everywhere Or maybe drop the compilation flag completely? void arch_livepatch_post_action(void); void arch_livepatch_mask(void); Cheers, -- Julien Grall Best Regards, Pawel Wieczorkiewicz Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Ralf Herbrich Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879