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 --- include/crypto/aes-ctr.h | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) create mode 100644 include/crypto/aes-ctr.h (limited to 'include/crypto/aes-ctr.h') diff --git a/include/crypto/aes-ctr.h b/include/crypto/aes-ctr.h new file mode 100644 index 000000000..8e214a857 --- /dev/null +++ b/include/crypto/aes-ctr.h @@ -0,0 +1,65 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * AES-CTR and AES-XCTR stream ciphers + * + * Copyright 2026 Google LLC + */ +#ifndef _CRYPTO_AES_CTR_H +#define _CRYPTO_AES_CTR_H + +#include + +/** + * aes_ctr() - AES-CTR en/decryption + * @dst: The destination buffer. Can be in-place or out-of-place. For other + * overlaps the behavior is unspecified. + * @src: The source data + * @len: Number of bytes to en/decrypt + * @ctr: The counter. It will be incremented by ceil(@len / AES_BLOCK_SIZE). + * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() + * + * This implements AES in counter mode with a 128-bit big endian counter. + * + * This exists only for use by the implementation of modes built on top of CTR + * (e.g., GCM and CCM) and some legacy protocols that use CTR mode directly. + * Callers are expected to know how to use CTR mode appropriately, including + * choosing (key, counter) pairs appropriately to avoid keystream reuse. + * + * This supports incremental en/decryption. The length of each non-final chunk + * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in + * each time. + * + * Context: Any context. + */ +void aes_ctr(u8 *dst, const u8 *src, size_t len, + u8 ctr[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); + +/** + * aes_xctr() - AES-XCTR en/decryption + * @dst: The destination buffer. Can be in-place or out-of-place. For other + * overlaps the behavior is unspecified. + * @src: The source data + * @len: Number of bytes to en/decrypt + * @ctr: The block counter (in host endianness). For the first call, set it to + * 1. It will be incremented by ceil(@len / AES_BLOCK_SIZE). + * @iv: The initialization vector + * @key: The key, already prepared using aes_preparekey() or aes_prepareenckey() + * + * This implements AES in XOR Counter mode, as specified in the paper + * "Length-preserving encryption with HCTR2" + * (https://eprint.iacr.org/2021/1441.pdf). + * + * This exists only for use by the implementation of modes built on top of XCTR. + * Callers are expected to know how to use XCTR mode appropriately, including + * choosing (key, IV) pairs appropriately to avoid keystream reuse. + * + * This supports incremental en/decryption. The length of each non-final chunk + * must be a multiple of AES_BLOCK_SIZE, and the updated @ctr must be passed in + * each time. + * + * Context: Any context. + */ +void aes_xctr(u8 *dst, const u8 *src, size_t len, u64 *ctr, + const u8 iv[at_least AES_BLOCK_SIZE], aes_encrypt_arg key); + +#endif /* _CRYPTO_AES_CTR_H */ -- cgit v1.3.1