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/crypto/tests/test-utils.h | 111 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 lib/crypto/tests/test-utils.h (limited to 'lib/crypto/tests/test-utils.h') diff --git a/lib/crypto/tests/test-utils.h b/lib/crypto/tests/test-utils.h new file mode 100644 index 000000000..73ca21f91 --- /dev/null +++ b/lib/crypto/tests/test-utils.h @@ -0,0 +1,111 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Test utility functions shared by the crypto library tests. + * + * For now this is simply a header that's included into the KUnit test suites + * that need it. If this gets too large it could be made its own translation + * unit and libcrypto_test_utils module, but that seems overkill for now. + */ +#ifndef LIB_CRYPTO_TEST_UTILS_H +#define LIB_CRYPTO_TEST_UTILS_H + +#include +#include +#include +#include +#include + +static u64 random_seed; + +static __maybe_unused void action_free_guarded_buf(void *buf) +{ + vfree(buf); +} + +/* + * Allocate a KUnit-managed buffer that has length @size bytes (> 0) immediately + * followed by an unmapped page, and assert that the allocation succeeds. + */ +static __maybe_unused void *alloc_guarded_buf(struct kunit *test, size_t size) +{ + size_t full_size = round_up(size, PAGE_SIZE); + void *buf = vmalloc(full_size); + + KUNIT_ASSERT_NOT_NULL(test, buf); + KUNIT_ASSERT_EQ(test, 0, + kunit_add_action_or_reset(test, action_free_guarded_buf, + buf)); + return buf + full_size - size; +} + +static __maybe_unused void *alloc_buf(struct kunit *test, size_t size) +{ + void *buf = kunit_kmalloc(test, size, GFP_KERNEL); + + KUNIT_ASSERT_NOT_NULL(test, buf); + return buf; +} + +static __maybe_unused void *memdup_buf(struct kunit *test, const void *src, + size_t size) +{ + void *dst = alloc_buf(test, size); + + return memcpy(dst, src, size); +} + +/* + * This is a simple linear congruential generator. It is used only for testing, + * which does not require cryptographically secure random numbers. A hard-coded + * algorithm is used instead of so that it matches the + * algorithm used by the test vector generation script. This allows the input + * data in random test vectors to be concisely stored as just the seed. + */ +static __maybe_unused u32 rand32(void) +{ + random_seed = (random_seed * 25214903917 + 11) & ((1ULL << 48) - 1); + return random_seed >> 16; +} + +static __maybe_unused void rand_bytes(u8 *out, size_t len) +{ + for (size_t i = 0; i < len; i++) + out[i] = rand32(); +} + +static __maybe_unused void rand_bytes_seeded_from_len(u8 *out, size_t len) +{ + random_seed = len; + rand_bytes(out, len); +} + +static __maybe_unused bool rand_bool(void) +{ + return rand32() % 2; +} + +/* Generate a random length, preferring small lengths. */ +static __maybe_unused size_t rand_length(size_t max_len) +{ + size_t len; + + switch (rand32() % 3) { + case 0: + len = rand32() % 128; + break; + case 1: + len = rand32() % 3072; + break; + default: + len = rand32(); + break; + } + return len % (max_len + 1); +} + +static __maybe_unused size_t rand_offset(size_t max_offset) +{ + return min(rand32() % 128, max_offset); +} + +#endif /* LIB_CRYPTO_TEST_UTILS_H */ -- cgit v1.3.1