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 --- drivers/base/map.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 154 insertions(+) create mode 100644 drivers/base/map.c (limited to 'drivers/base/map.c') diff --git a/drivers/base/map.c b/drivers/base/map.c new file mode 100644 index 000000000..bde415f93 --- /dev/null +++ b/drivers/base/map.c @@ -0,0 +1,154 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * linux/drivers/base/map.c + * + * (C) Copyright Al Viro 2002,2003 + * + * NOTE: data structure needs to be changed. It works, but for large dev_t + * it will be too slow. It is isolated, though, so these changes will be + * local to that file. + */ + +#include +#include +#include +#include +#include +#include + +struct kobj_map { + struct probe { + struct probe *next; + dev_t dev; + unsigned long range; + struct module *owner; + kobj_probe_t *get; + int (*lock)(dev_t, void *); + void *data; + } *probes[255]; + struct mutex *lock; +}; + +int kobj_map(struct kobj_map *domain, dev_t dev, unsigned long range, + struct module *module, kobj_probe_t *probe, + int (*lock)(dev_t, void *), void *data) +{ + unsigned int n = MAJOR(dev + range - 1) - MAJOR(dev) + 1; + unsigned int index = MAJOR(dev); + unsigned int i; + struct probe *p; + + if (n > 255) + n = 255; + + p = kmalloc_objs(struct probe, n); + if (p == NULL) + return -ENOMEM; + + for (i = 0; i < n; i++, p++) { + p->owner = module; + p->get = probe; + p->lock = lock; + p->dev = dev; + p->range = range; + p->data = data; + } + mutex_lock(domain->lock); + for (i = 0, p -= n; i < n; i++, p++, index++) { + struct probe **s = &domain->probes[index % 255]; + while (*s && (*s)->range < range) + s = &(*s)->next; + p->next = *s; + *s = p; + } + mutex_unlock(domain->lock); + return 0; +} + +void kobj_unmap(struct kobj_map *domain, dev_t dev, unsigned long range) +{ + unsigned int n = MAJOR(dev + range - 1) - MAJOR(dev) + 1; + unsigned int index = MAJOR(dev); + unsigned int i; + struct probe *found = NULL; + + if (n > 255) + n = 255; + + mutex_lock(domain->lock); + for (i = 0; i < n; i++, index++) { + struct probe **s; + for (s = &domain->probes[index % 255]; *s; s = &(*s)->next) { + struct probe *p = *s; + if (p->dev == dev && p->range == range) { + *s = p->next; + if (!found) + found = p; + break; + } + } + } + mutex_unlock(domain->lock); + kfree(found); +} + +struct kobject *kobj_lookup(struct kobj_map *domain, dev_t dev, int *index) +{ + struct kobject *kobj; + struct probe *p; + unsigned long best = ~0UL; + +retry: + mutex_lock(domain->lock); + for (p = domain->probes[MAJOR(dev) % 255]; p; p = p->next) { + struct kobject *(*probe)(dev_t, int *, void *); + struct module *owner; + void *data; + + if (p->dev > dev || p->dev + p->range - 1 < dev) + continue; + if (p->range - 1 >= best) + break; + if (!try_module_get(p->owner)) + continue; + owner = p->owner; + data = p->data; + probe = p->get; + best = p->range - 1; + *index = dev - p->dev; + if (p->lock && p->lock(dev, data) < 0) { + module_put(owner); + continue; + } + mutex_unlock(domain->lock); + kobj = probe(dev, index, data); + /* Currently ->owner protects _only_ ->probe() itself. */ + module_put(owner); + if (kobj) + return kobj; + goto retry; + } + mutex_unlock(domain->lock); + return NULL; +} + +struct kobj_map *kobj_map_init(kobj_probe_t *base_probe, struct mutex *lock) +{ + struct kobj_map *p = kmalloc_obj(struct kobj_map); + struct probe *base = kzalloc_obj(*base); + int i; + + if ((p == NULL) || (base == NULL)) { + kfree(p); + kfree(base); + return NULL; + } + + base->dev = 1; + base->range = ~0; + base->get = base_probe; + for (i = 0; i < 255; i++) + p->probes[i] = base; + p->lock = lock; + return p; +} -- cgit v1.3.1