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, 71 insertions, 0 deletions

diff --git a/drivers/crypto/qce/sha.h b/drivers/crypto/qce/sha.h
new file mode 100644
index 000000000..cb822fc33
--- /dev/null
+++ b/drivers/crypto/qce/sha.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
+ */
+
+#ifndef _SHA_H_
+#define _SHA_H_
+
+#include <crypto/scatterwalk.h>
+#include <crypto/sha2.h>
+
+#include "common.h"
+#include "core.h"
+
+#define QCE_SHA_MAX_BLOCKSIZE		SHA256_BLOCK_SIZE
+#define QCE_SHA_MAX_DIGESTSIZE		SHA256_DIGEST_SIZE
+
+struct qce_sha_ctx {
+	u8 authkey[QCE_SHA_MAX_BLOCKSIZE];
+};
+
+/**
+ * struct qce_sha_reqctx - holds private ahash objects per request
+ * @buf: used during update, import and export
+ * @tmpbuf: buffer for internal use
+ * @digest: calculated digest buffer
+ * @buflen: length of the buffer
+ * @flags: operation flags
+ * @src_orig: original request sg list
+ * @nbytes_orig: original request number of bytes
+ * @src_nents: source number of entries
+ * @byte_count: byte count
+ * @count: save count in states during update, import and export
+ * @first_blk: is it the first block
+ * @last_blk: is it the last block
+ * @sg: used to chain sg lists
+ * @authkey: pointer to auth key in sha ctx
+ * @authklen: auth key length
+ * @result_sg: scatterlist used for result buffer
+ */
+struct qce_sha_reqctx {
+	u8 buf[QCE_SHA_MAX_BLOCKSIZE];
+	u8 tmpbuf[QCE_SHA_MAX_BLOCKSIZE];
+	u8 digest[QCE_SHA_MAX_DIGESTSIZE];
+	unsigned int buflen;
+	unsigned long flags;
+	struct scatterlist *src_orig;
+	unsigned int nbytes_orig;
+	int src_nents;
+	__be32 byte_count[2];
+	u64 count;
+	bool first_blk;
+	bool last_blk;
+	struct scatterlist sg[2];
+	u8 *authkey;
+	unsigned int authklen;
+	struct scatterlist result_sg;
+};
+
+static inline struct qce_alg_template *to_ahash_tmpl(struct crypto_tfm *tfm)
+{
+	struct crypto_ahash *ahash = __crypto_ahash_cast(tfm);
+	struct ahash_alg *alg = container_of(crypto_hash_alg_common(ahash),
+					     struct ahash_alg, halg);
+
+	return container_of(alg, struct qce_alg_template, alg.ahash);
+}
+
+extern const struct qce_algo_ops ahash_ops;
+
+#endif /* _SHA_H_ */