KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

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 <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 156 insertions, 0 deletions

diff --git a/include/crypto/blake2b.h b/include/crypto/blake2b.h
new file mode 100644
index 000000000..3bc37fd10
--- /dev/null
+++ b/include/crypto/blake2b.h
@@ -0,0 +1,156 @@
+/* SPDX-License-Identifier: GPL-2.0 OR MIT */
+
+#ifndef _CRYPTO_BLAKE2B_H
+#define _CRYPTO_BLAKE2B_H
+
+#include <linux/bug.h>
+#include <linux/types.h>
+#include <linux/string.h>
+
+enum blake2b_lengths {
+	BLAKE2B_BLOCK_SIZE = 128,
+	BLAKE2B_HASH_SIZE = 64,
+	BLAKE2B_KEY_SIZE = 64,
+
+	BLAKE2B_160_HASH_SIZE = 20,
+	BLAKE2B_256_HASH_SIZE = 32,
+	BLAKE2B_384_HASH_SIZE = 48,
+	BLAKE2B_512_HASH_SIZE = 64,
+};
+
+/**
+ * struct blake2b_ctx - Context for hashing a message with BLAKE2b
+ * @h: compression function state
+ * @t: block counter
+ * @f: finalization indicator
+ * @buf: partial block buffer; 'buflen' bytes are valid
+ * @buflen: number of bytes buffered in @buf
+ * @outlen: length of output hash value in bytes, at most BLAKE2B_HASH_SIZE
+ */
+struct blake2b_ctx {
+	/* 'h', 't', and 'f' are used in assembly code, so keep them as-is. */
+	u64 h[8];
+	u64 t[2];
+	u64 f[2];
+	u8 buf[BLAKE2B_BLOCK_SIZE];
+	unsigned int buflen;
+	unsigned int outlen;
+};
+
+enum blake2b_iv {
+	BLAKE2B_IV0 = 0x6A09E667F3BCC908ULL,
+	BLAKE2B_IV1 = 0xBB67AE8584CAA73BULL,
+	BLAKE2B_IV2 = 0x3C6EF372FE94F82BULL,
+	BLAKE2B_IV3 = 0xA54FF53A5F1D36F1ULL,
+	BLAKE2B_IV4 = 0x510E527FADE682D1ULL,
+	BLAKE2B_IV5 = 0x9B05688C2B3E6C1FULL,
+	BLAKE2B_IV6 = 0x1F83D9ABFB41BD6BULL,
+	BLAKE2B_IV7 = 0x5BE0CD19137E2179ULL,
+};
+
+static inline void __blake2b_init(struct blake2b_ctx *ctx, size_t outlen,
+				  const void *key, size_t keylen)
+{
+	ctx->h[0] = BLAKE2B_IV0 ^ (0x01010000 | keylen << 8 | outlen);
+	ctx->h[1] = BLAKE2B_IV1;
+	ctx->h[2] = BLAKE2B_IV2;
+	ctx->h[3] = BLAKE2B_IV3;
+	ctx->h[4] = BLAKE2B_IV4;
+	ctx->h[5] = BLAKE2B_IV5;
+	ctx->h[6] = BLAKE2B_IV6;
+	ctx->h[7] = BLAKE2B_IV7;
+	ctx->t[0] = 0;
+	ctx->t[1] = 0;
+	ctx->f[0] = 0;
+	ctx->f[1] = 0;
+	ctx->buflen = 0;
+	ctx->outlen = outlen;
+	if (keylen) {
+		memcpy(ctx->buf, key, keylen);
+		memset(&ctx->buf[keylen], 0, BLAKE2B_BLOCK_SIZE - keylen);
+		ctx->buflen = BLAKE2B_BLOCK_SIZE;
+	}
+}
+
+/**
+ * blake2b_init() - Initialize a BLAKE2b context for a new message (unkeyed)
+ * @ctx: the context to initialize
+ * @outlen: length of output hash value in bytes, at most BLAKE2B_HASH_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2b_init(struct blake2b_ctx *ctx, size_t outlen)
+{
+	__blake2b_init(ctx, outlen, NULL, 0);
+}
+
+/**
+ * blake2b_init_key() - Initialize a BLAKE2b context for a new message (keyed)
+ * @ctx: the context to initialize
+ * @outlen: length of output hash value in bytes, at most BLAKE2B_HASH_SIZE
+ * @key: the key
+ * @keylen: the key length in bytes, at most BLAKE2B_KEY_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2b_init_key(struct blake2b_ctx *ctx, size_t outlen,
+				    const void *key, size_t keylen)
+{
+	WARN_ON(IS_ENABLED(DEBUG) && (!outlen || outlen > BLAKE2B_HASH_SIZE ||
+		!key || !keylen || keylen > BLAKE2B_KEY_SIZE));
+
+	__blake2b_init(ctx, outlen, key, keylen);
+}
+
+/**
+ * blake2b_update() - Update a BLAKE2b context with message data
+ * @ctx: the context to update; must have been initialized
+ * @in: the message data
+ * @inlen: the data length in bytes
+ *
+ * This can be called any number of times.
+ *
+ * Context: Any context.
+ */
+void blake2b_update(struct blake2b_ctx *ctx, const u8 *in, size_t inlen);
+
+/**
+ * blake2b_final() - Finish computing a BLAKE2b hash
+ * @ctx: the context to finalize; must have been initialized
+ * @out: (output) the resulting BLAKE2b hash.  Its length will be equal to the
+ *	 @outlen that was passed to blake2b_init() or blake2b_init_key().
+ *
+ * After finishing, this zeroizes @ctx.  So the caller does not need to do it.
+ *
+ * Context: Any context.
+ */
+void blake2b_final(struct blake2b_ctx *ctx, u8 *out);
+
+/**
+ * blake2b() - Compute BLAKE2b hash in one shot
+ * @key: the key, or NULL for an unkeyed hash
+ * @keylen: the key length in bytes (at most BLAKE2B_KEY_SIZE), or 0 for an
+ *	    unkeyed hash
+ * @in: the message data
+ * @inlen: the data length in bytes
+ * @out: (output) the resulting BLAKE2b hash, with length @outlen
+ * @outlen: length of output hash value in bytes, at most BLAKE2B_HASH_SIZE
+ *
+ * Context: Any context.
+ */
+static inline void blake2b(const u8 *key, size_t keylen,
+			   const u8 *in, size_t inlen,
+			   u8 *out, size_t outlen)
+{
+	struct blake2b_ctx ctx;
+
+	WARN_ON(IS_ENABLED(DEBUG) && ((!in && inlen > 0) || !out || !outlen ||
+		outlen > BLAKE2B_HASH_SIZE || keylen > BLAKE2B_KEY_SIZE ||
+		(!key && keylen)));
+
+	__blake2b_init(&ctx, outlen, key, keylen);
+	blake2b_update(&ctx, in, inlen);
+	blake2b_final(&ctx, out);
+}
+
+#endif /* _CRYPTO_BLAKE2B_H */