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 --- lib/timerqueue.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) create mode 100644 lib/timerqueue.c (limited to 'lib/timerqueue.c') diff --git a/lib/timerqueue.c b/lib/timerqueue.c new file mode 100644 index 000000000..e2a1e08cb --- /dev/null +++ b/lib/timerqueue.c @@ -0,0 +1,98 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Generic Timer-queue + * + * Manages a simple queue of timers, ordered by expiration time. + * Uses rbtrees for quick list adds and expiration. + * + * NOTE: All of the following functions need to be serialized + * to avoid races. No locking is done by this library code. + */ + +#include +#include +#include +#include + +#define __node_2_tq(_n) \ + rb_entry((_n), struct timerqueue_node, node) + +static inline bool __timerqueue_less(struct rb_node *a, const struct rb_node *b) +{ + return __node_2_tq(a)->expires < __node_2_tq(b)->expires; +} + +/** + * timerqueue_add - Adds timer to timerqueue. + * + * @head: head of timerqueue + * @node: timer node to be added + * + * Adds the timer node to the timerqueue, sorted by the node's expires + * value. Returns true if the newly added timer is the first expiring timer in + * the queue. + */ +bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node) +{ + /* Make sure we don't add nodes that are already added */ + WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node)); + + return rb_add_cached(&node->node, &head->rb_root, __timerqueue_less); +} +EXPORT_SYMBOL_GPL(timerqueue_add); + +/** + * timerqueue_del - Removes a timer from the timerqueue. + * + * @head: head of timerqueue + * @node: timer node to be removed + * + * Removes the timer node from the timerqueue. Returns true if the queue is + * not empty after the remove. + */ +bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node) +{ + WARN_ON_ONCE(RB_EMPTY_NODE(&node->node)); + + rb_erase_cached(&node->node, &head->rb_root); + RB_CLEAR_NODE(&node->node); + + return !RB_EMPTY_ROOT(&head->rb_root.rb_root); +} +EXPORT_SYMBOL_GPL(timerqueue_del); + +/** + * timerqueue_iterate_next - Returns the timer after the provided timer + * + * @node: Pointer to a timer. + * + * Provides the timer that is after the given node. This is used, when + * necessary, to iterate through the list of timers in a timer list + * without modifying the list. + */ +struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node) +{ + struct rb_node *next; + + if (!node) + return NULL; + next = rb_next(&node->node); + if (!next) + return NULL; + return container_of(next, struct timerqueue_node, node); +} +EXPORT_SYMBOL_GPL(timerqueue_iterate_next); + +#define __node_2_tq_linked(_n) \ + container_of(rb_entry((_n), struct rb_node_linked, node), struct timerqueue_linked_node, node) + +static __always_inline bool __tq_linked_less(struct rb_node *a, const struct rb_node *b) +{ + return __node_2_tq_linked(a)->expires < __node_2_tq_linked(b)->expires; +} + +bool timerqueue_linked_add(struct timerqueue_linked_head *head, struct timerqueue_linked_node *node) +{ + return rb_add_linked(&node->node, &head->rb_root, __tq_linked_less); +} +EXPORT_SYMBOL_GPL(timerqueue_linked_add); -- cgit v1.3.1