From 93de2a6a4b91b72607136dd656edf03fb399d27f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2026 09:37:21 -0700 Subject: KVM: SEV: Do cache maintenance on the source VM during intra-host migration Manually perform cache maintenance on the source VM during intra-host migration to ensure no stale data is left in CPU caches after the VM is destroyed. Because the source VM is "converted" to a non-SEV VM, KVM's memory reclaim flows won't trigger cache maintenance, e.g. when all guest memory is reclaimed in response to detaching from the mmu_notifier. Note, relying on the destination VM to do cache maintenance isn't an option as KVM doesn't require identical guest memory configurations, i.e. the source VM may have access to memory that the destination VM does not. Enforcing equivalent memory configurations is infeasible, as it would require a *deep* comparison of memslots, e.g. to verify that not only are the memslot identical, but what the memslots point at is also identical. Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration") Cc: stable@vger.kernel.org Reported-by: Stefan Teodorescu Signed-off-by: Sean Christopherson Message-ID: <20260923163721.1584779-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- scripts/livepatch/init.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 106 insertions(+) create mode 100644 scripts/livepatch/init.c (limited to 'scripts/livepatch/init.c') diff --git a/scripts/livepatch/init.c b/scripts/livepatch/init.c new file mode 100644 index 000000000..16aff8f73 --- /dev/null +++ b/scripts/livepatch/init.c @@ -0,0 +1,106 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Init code for a livepatch kernel module + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include +#include +#include + +static struct klp_patch *patch; + +static int __init livepatch_mod_init(void) +{ + struct klp_object_ext *obj_exts; + size_t obj_exts_sec_size; + struct klp_object *objs; + unsigned int nr_objs; + int ret; + + obj_exts = klp_find_section_by_name(THIS_MODULE, ".init.klp_objects", + &obj_exts_sec_size); + nr_objs = obj_exts_sec_size / sizeof(*obj_exts); + if (!nr_objs) { + pr_err("nothing to patch!\n"); + ret = -EINVAL; + goto err; + } + + patch = kzalloc_obj(*patch); + if (!patch) { + ret = -ENOMEM; + goto err; + } + + objs = kzalloc(sizeof(struct klp_object) * (nr_objs + 1), GFP_KERNEL); + if (!objs) { + ret = -ENOMEM; + goto err_free_patch; + } + + for (int i = 0; i < nr_objs; i++) { + struct klp_object_ext *obj_ext = obj_exts + i; + struct klp_func_ext *funcs_ext = obj_ext->funcs; + unsigned int nr_funcs = obj_ext->nr_funcs; + struct klp_func *funcs = objs[i].funcs; + struct klp_object *obj = objs + i; + + funcs = kzalloc(sizeof(struct klp_func) * (nr_funcs + 1), GFP_KERNEL); + if (!funcs) { + ret = -ENOMEM; + for (int j = 0; j < i; j++) + kfree(objs[j].funcs); + goto err_free_objs; + } + + for (int j = 0; j < nr_funcs; j++) { + funcs[j].old_name = funcs_ext[j].old_name; + funcs[j].new_func = funcs_ext[j].new_func; + funcs[j].old_sympos = funcs_ext[j].sympos; + } + + obj->name = obj_ext->name; + obj->funcs = funcs; + + memcpy(&obj->callbacks, &obj_ext->callbacks, sizeof(struct klp_callbacks)); + } + + patch->mod = THIS_MODULE; + patch->objs = objs; + + /* TODO patch->states */ + +#ifdef KLP_NO_REPLACE + patch->replace = false; +#else + patch->replace = true; +#endif + + return klp_enable_patch(patch); + +err_free_objs: + kfree(objs); +err_free_patch: + kfree(patch); +err: + return ret; +} + +static void __exit livepatch_mod_exit(void) +{ + struct klp_object *obj; + + klp_for_each_object_static(patch, obj) + kfree(obj->funcs); + + kfree(patch->objs); + kfree(patch); +} + +module_init(livepatch_mod_init); +module_exit(livepatch_mod_exit); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y"); +MODULE_DESCRIPTION("Livepatch module"); -- cgit v1.3.1