KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 274 insertions, 0 deletions

diff --git a/include/crypto/if_alg.h b/include/crypto/if_alg.h
new file mode 100644
index 000000000..0d51428c1
--- /dev/null
+++ b/include/crypto/if_alg.h
@@ -0,0 +1,274 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * if_alg: User-space algorithm interface
+ *
+ * Copyright (c) 2010 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#ifndef _CRYPTO_IF_ALG_H
+#define _CRYPTO_IF_ALG_H
+
+#include <linux/bits.h>
+#include <linux/compiler.h>
+#include <linux/completion.h>
+#include <linux/if_alg.h>
+#include <linux/scatterlist.h>
+#include <linux/types.h>
+#include <linux/atomic.h>
+#include <net/sock.h>
+
+#include <crypto/aead.h>
+#include <crypto/skcipher.h>
+
+#define ALG_MAX_PAGES			16
+
+struct alg_sock {
+	/* struct sock must be the first member of struct alg_sock */
+	struct sock sk;
+
+	struct sock *parent;
+
+	atomic_t refcnt;
+	atomic_t nokey_refcnt;
+
+	const struct af_alg_type *type;
+	void *private;
+};
+
+struct af_alg_control {
+	struct af_alg_iv *iv;
+	int op;
+	unsigned int aead_assoclen;
+};
+
+struct af_alg_type {
+	void *(*bind)(const char *name);
+	void (*release)(void *private);
+	int (*setkey)(void *private, const u8 *key, unsigned int keylen);
+	int (*setentropy)(void *private, sockptr_t entropy, unsigned int len);
+	int (*accept)(void *private, struct sock *sk);
+	int (*accept_nokey)(void *private, struct sock *sk);
+	int (*setauthsize)(void *private, unsigned int authsize);
+
+	struct proto_ops *ops;
+	struct proto_ops *ops_nokey;
+	struct module *owner;
+	char name[14];
+};
+
+struct af_alg_sgl {
+	struct sg_table sgt;
+	struct scatterlist sgl[ALG_MAX_PAGES + 1];
+	bool need_unpin;
+};
+
+/* TX SGL entry */
+struct af_alg_tsgl {
+	struct list_head list;
+	unsigned int cur;		/* Last processed SG entry */
+	struct scatterlist sg[];	/* Array of SGs forming the SGL */
+};
+
+#define MAX_SGL_ENTS ((4096 - sizeof(struct af_alg_tsgl)) / \
+		      sizeof(struct scatterlist) - 1)
+
+/* RX SGL entry */
+struct af_alg_rsgl {
+	struct af_alg_sgl sgl;
+	struct list_head list;
+	size_t sg_num_bytes;		/* Bytes of data in that SGL */
+};
+
+/**
+ * struct af_alg_async_req - definition of crypto request
+ * @sk:			Socket the request is associated with
+ * @first_rsgl:		First RX SG
+ * @last_rsgl:		Pointer to last RX SG
+ * @rsgl_list:		Track RX SGs
+ * @tsgl:		Private, per request TX SGL of buffers to process
+ * @tsgl_entries:	Number of entries in priv. TX SGL
+ * @outlen:		Number of output bytes generated by crypto op
+ * @areqlen:		Length of this data structure
+ * @cra_u:		Cipher request
+ */
+struct af_alg_async_req {
+	struct sock *sk;
+
+	struct af_alg_rsgl first_rsgl;
+	struct af_alg_rsgl *last_rsgl;
+	struct list_head rsgl_list;
+
+	struct scatterlist *tsgl;
+	unsigned int tsgl_entries;
+
+	unsigned int outlen;
+	unsigned int areqlen;
+
+	union {
+		struct aead_request aead_req;
+		struct skcipher_request skcipher_req;
+	} cra_u;
+
+	/* req ctx trails this struct */
+};
+
+/**
+ * struct af_alg_ctx - definition of the crypto context
+ *
+ * The crypto context tracks the input data during the lifetime of an AF_ALG
+ * socket.
+ *
+ * @tsgl_list:		Link to TX SGL
+ * @iv:			IV for cipher operation
+ * @state:		Existing state for continuing operation
+ * @aead_assoclen:	Length of AAD for AEAD cipher operations
+ * @wait:		For waiting for completion of async crypto ops
+ * @used:		TX bytes sent to kernel. This variable is used to
+ *			ensure that user space cannot cause the kernel
+ *			to allocate too much memory in sendmsg operation.
+ * @rcvused:		Total RX bytes to be filled by kernel. This variable
+ *			is used to ensure user space cannot cause the kernel
+ *			to allocate too much memory in a recvmsg operation.
+ * @more:		More data to be expected from user space?
+ * @merge:		Shall new data from user space be merged into existing
+ *			SG?
+ * @enc:		Cryptographic operation to be performed when
+ *			recvmsg is invoked.
+ * @write:		True if we are in the middle of a write.
+ * @init:		True if metadata has been sent.
+ * @len:		Length of memory allocated for this data structure.
+ * @inflight:		Non-zero when requests are in flight, for debugging only.
+ */
+struct af_alg_ctx {
+	struct list_head tsgl_list;
+
+	void *iv;
+	void *state;
+	size_t aead_assoclen;
+
+	struct crypto_wait wait;
+
+	size_t used;
+	atomic_t rcvused;
+
+	bool		more:1,
+			merge:1,
+			enc:1,
+			write:1,
+			init:1;
+
+	unsigned int len;
+
+	unsigned int inflight;
+};
+
+/* Flags for af_alg_allowlist_entry::flags: */
+#define AF_ALG_UNPRIVILEGED BIT(0) /* Unprivileged use is allowed */
+
+struct af_alg_allowlist_entry {
+	const char *name;
+	u32 flags;
+};
+
+int af_alg_register_type(const struct af_alg_type *type);
+int af_alg_unregister_type(const struct af_alg_type *type);
+
+int af_alg_check_restriction(const char *name,
+			     const struct af_alg_allowlist_entry allowlist[]);
+
+int af_alg_release(struct socket *sock);
+void af_alg_release_parent(struct sock *sk);
+int af_alg_accept(struct sock *sk, struct socket *newsock,
+		  struct proto_accept_arg *arg);
+
+void af_alg_free_sg(struct af_alg_sgl *sgl);
+
+static inline struct alg_sock *alg_sk(struct sock *sk)
+{
+	return (struct alg_sock *)sk;
+}
+
+/**
+ * af_alg_sndbuf - Size of available buffer for sending data from user space to kernel.
+ *
+ * @sk: socket of connection to user space
+ *
+ * Returns: number of bytes still available
+ */
+static inline int af_alg_sndbuf(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct af_alg_ctx *ctx = ask->private;
+
+	return max_t(int, max_t(int, sk->sk_sndbuf & PAGE_MASK, PAGE_SIZE) -
+			  ctx->used, 0);
+}
+
+/**
+ * af_alg_writable - Can the send buffer still be written to?
+ *
+ * @sk: socket of connection to user space
+ *
+ * Returns: true => writable, false => not writable
+ */
+static inline bool af_alg_writable(struct sock *sk)
+{
+	return PAGE_SIZE <= af_alg_sndbuf(sk);
+}
+
+/**
+ * af_alg_rcvbuf - Size of available buffer used by kernel for the RX user space operation.
+ *
+ * @sk: socket of connection to user space
+ *
+ * Returns: number of bytes still available
+ */
+static inline int af_alg_rcvbuf(struct sock *sk)
+{
+	struct alg_sock *ask = alg_sk(sk);
+	struct af_alg_ctx *ctx = ask->private;
+
+	return max_t(int, max_t(int, sk->sk_rcvbuf & PAGE_MASK, PAGE_SIZE) -
+		     atomic_read(&ctx->rcvused), 0);
+}
+
+/**
+ * af_alg_readable - Can the RX buffer still be read from?
+ *
+ * @sk: socket of connection to user space
+ *
+ * Returns: true => readable, false => not readable
+ */
+static inline bool af_alg_readable(struct sock *sk)
+{
+	return PAGE_SIZE <= af_alg_rcvbuf(sk);
+}
+
+unsigned int af_alg_count_tsgl(struct sock *sk, size_t bytes);
+void af_alg_pull_tsgl(struct sock *sk, size_t used, struct scatterlist *dst);
+void af_alg_wmem_wakeup(struct sock *sk);
+int af_alg_wait_for_data(struct sock *sk, unsigned flags, unsigned min);
+int af_alg_sendmsg(struct socket *sock, struct msghdr *msg, size_t size,
+		   unsigned int ivsize);
+void af_alg_free_resources(struct af_alg_async_req *areq);
+__poll_t af_alg_poll(struct file *file, struct socket *sock,
+			 poll_table *wait);
+struct af_alg_async_req *af_alg_alloc_areq(struct sock *sk,
+					   unsigned int areqlen);
+int af_alg_get_rsgl(struct sock *sk, struct msghdr *msg, int flags,
+		    struct af_alg_async_req *areq, size_t maxsize,
+		    size_t *outlen);
+
+/*
+ * Mask used to disable unsupported algorithm implementations.
+ *
+ * This is the same as FSCRYPT_CRYPTOAPI_MASK in fs/crypto/fscrypt_private.h.
+ * In additions to the motivations there, this API is exposed to userspace
+ * that might not be fully trusted.
+ */
+#define AF_ALG_CRYPTOAPI_MASK                             \
+	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_ALLOCATES_MEMORY | \
+	 CRYPTO_ALG_KERN_DRIVER_ONLY)
+
+
+#endif	/* _CRYPTO_IF_ALG_H */