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 --- io_uring/alloc_cache.h | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 70 insertions(+) create mode 100644 io_uring/alloc_cache.h (limited to 'io_uring/alloc_cache.h') diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h new file mode 100644 index 000000000..962b6e2d0 --- /dev/null +++ b/io_uring/alloc_cache.h @@ -0,0 +1,70 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef IOU_ALLOC_CACHE_H +#define IOU_ALLOC_CACHE_H + +#include +#include + +/* + * Don't allow the cache to grow beyond this size. + */ +#define IO_ALLOC_CACHE_MAX 128 + +void io_alloc_cache_free(struct io_alloc_cache *cache, + void (*free)(const void *)); +bool io_alloc_cache_init(struct io_alloc_cache *cache, + unsigned max_nr, unsigned int size, + unsigned int init_bytes); + +void *io_cache_alloc_new(struct io_alloc_cache *cache, gfp_t gfp); + +static inline bool io_alloc_cache_put(struct io_alloc_cache *cache, + void *entry) +{ + if (cache->nr_cached < cache->max_cached) { + if (!kasan_mempool_poison_object(entry)) + return false; + cache->entries[cache->nr_cached++] = entry; + return true; + } + return false; +} + +static inline void *io_alloc_cache_get(struct io_alloc_cache *cache) +{ + if (cache->nr_cached) { + void *entry = cache->entries[--cache->nr_cached]; + + /* + * If KASAN is enabled, always clear the initial bytes that + * must be zeroed post alloc, in case any of them overlap + * with KASAN storage. + */ +#if defined(CONFIG_KASAN) + kasan_mempool_unpoison_object(entry, cache->elem_size); + if (cache->init_clear) + memset(entry, 0, cache->init_clear); +#endif + return entry; + } + + return NULL; +} + +static inline void *io_cache_alloc(struct io_alloc_cache *cache, gfp_t gfp) +{ + void *obj; + + obj = io_alloc_cache_get(cache); + if (obj) + return obj; + return io_cache_alloc_new(cache, gfp); +} + +static inline void io_cache_free(struct io_alloc_cache *cache, void *obj) +{ + if (!io_alloc_cache_put(cache, obj)) + kvfree(obj); +} + +#endif -- cgit v1.3.1