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/utils.c | 90 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 lib/crypto/utils.c (limited to 'lib/crypto/utils.c') diff --git a/lib/crypto/utils.c b/lib/crypto/utils.c new file mode 100644 index 000000000..dec381d5e --- /dev/null +++ b/lib/crypto/utils.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Crypto library utility functions + * + * Copyright (c) 2006 Herbert Xu + */ + +#include +#include +#include +#include + +/* + * XOR @len bytes from @src1 and @src2 together, writing the result to @dst + * (which may alias one of the sources). Don't call this directly; call + * crypto_xor() or crypto_xor_cpy() instead. + */ +void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int len) +{ + int relalign = 0; + + if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { + int size = sizeof(unsigned long); + int d = (((unsigned long)dst ^ (unsigned long)src1) | + ((unsigned long)dst ^ (unsigned long)src2)) & + (size - 1); + + relalign = d ? 1 << __ffs(d) : size; + + /* + * If we care about alignment, process as many bytes as + * needed to advance dst and src to values whose alignments + * equal their relative alignment. This will allow us to + * process the remainder of the input using optimal strides. + */ + while (((unsigned long)dst & (relalign - 1)) && len > 0) { + *dst++ = *src1++ ^ *src2++; + len--; + } + } + + while (IS_ENABLED(CONFIG_64BIT) && len >= 8 && !(relalign & 7)) { + if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { + u64 l = get_unaligned((u64 *)src1) ^ + get_unaligned((u64 *)src2); + put_unaligned(l, (u64 *)dst); + } else { + *(u64 *)dst = *(u64 *)src1 ^ *(u64 *)src2; + } + dst += 8; + src1 += 8; + src2 += 8; + len -= 8; + } + + while (len >= 4 && !(relalign & 3)) { + if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { + u32 l = get_unaligned((u32 *)src1) ^ + get_unaligned((u32 *)src2); + put_unaligned(l, (u32 *)dst); + } else { + *(u32 *)dst = *(u32 *)src1 ^ *(u32 *)src2; + } + dst += 4; + src1 += 4; + src2 += 4; + len -= 4; + } + + while (len >= 2 && !(relalign & 1)) { + if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) { + u16 l = get_unaligned((u16 *)src1) ^ + get_unaligned((u16 *)src2); + put_unaligned(l, (u16 *)dst); + } else { + *(u16 *)dst = *(u16 *)src1 ^ *(u16 *)src2; + } + dst += 2; + src1 += 2; + src2 += 2; + len -= 2; + } + + while (len--) + *dst++ = *src1++ ^ *src2++; +} +EXPORT_SYMBOL_GPL(__crypto_xor); + +MODULE_DESCRIPTION("Crypto library utility functions"); +MODULE_LICENSE("GPL"); -- cgit v1.3.1