diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index f672c34..7acf20e 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5918,16 +5918,87 @@ out:
 }
 
 /*
- * nfs4_proc_exchange_id()
+ * Minimum set of SP4_MACH_CRED operations from RFC 5661
+ */
+static const struct nfs41_state_protection nfs4_sp4_mach_cred_request = {
+	.how = SP4_MACH_CRED,
+	.enforce.u.words = {
+		[1] = 1 << (OP_BIND_CONN_TO_SESSION - 32) |
+		      1 << (OP_EXCHANGE_ID - 32) |
+		      1 << (OP_CREATE_SESSION - 32) |
+		      1 << (OP_DESTROY_SESSION - 32) |
+		      1 << (OP_DESTROY_CLIENTID - 32)
+	}
+};
+
+/*
+ * Select the state protection mode for client `clp' given the server results
+ * from exchange_id in `sp'.
  *
- * Returns zero, a negative errno, or a negative NFS4ERR status code.
+ * Returns 0 on success, negative errno otherwise.
+ */
+static int nfs4_sp4_select_mode(struct nfs_client *clp,
+				 struct nfs41_state_protection *sp)
+{
+	static const u32 supported_enforce[NFS4_OP_MAP_NUM_WORDS] = {
+		[1] = 1 << (OP_BIND_CONN_TO_SESSION - 32) |
+		      1 << (OP_EXCHANGE_ID - 32) |
+		      1 << (OP_CREATE_SESSION - 32) |
+		      1 << (OP_DESTROY_SESSION - 32) |
+		      1 << (OP_DESTROY_CLIENTID - 32)
+	};
+	unsigned int i;
+
+	if (sp->how == SP4_MACH_CRED) {
+		/* Print state protect result */
+		dfprintk(MOUNT, "Server SP4_MACH_CRED support:\n");
+		for (i = 0; i <= LAST_NFS4_OP; i++) {
+			if (test_bit(i, sp->enforce.u.longs))
+				dfprintk(MOUNT, "  enforce op %d\n", i);
+			if (test_bit(i, sp->allow.u.longs))
+				dfprintk(MOUNT, "  allow op %d\n", i);
+		}
+
+		/* make sure nothing is on enforce list that isn't supported */
+		for (i = 0; i < NFS4_OP_MAP_NUM_WORDS; i++) {
+			if (sp->enforce.u.words[i] & ~supported_enforce[i]) {
+				dfprintk(MOUNT, "sp4_mach_cred: disabled\n");
+				return -EINVAL;
+			}
+		}
+
+		/*
+		 * Minimal mode - state operations are allowed to use machine
+		 * credential.  Note this already happens by default, so the
+		 * client doesn't have to do anything more than the negotiation.
+		 *
+		 * NOTE: we don't care if EXCHANGE_ID is in the list -
+		 *       we're already using the machine cred for exchange_id
+		 *       and will never use a different cred.
+		 */
+		if (test_bit(OP_BIND_CONN_TO_SESSION, sp->enforce.u.longs) &&
+		    test_bit(OP_CREATE_SESSION, sp->enforce.u.longs) &&
+		    test_bit(OP_DESTROY_SESSION, sp->enforce.u.longs) &&
+		    test_bit(OP_DESTROY_CLIENTID, sp->enforce.u.longs)) {
+			dfprintk(MOUNT, "sp4_mach_cred:\n");
+			dfprintk(MOUNT, "  minimal mode enabled\n");
+			set_bit(NFS_SP4_MACH_CRED_MINIMAL, &clp->cl_sp4_flags);
+		} else {
+			dfprintk(MOUNT, "sp4_mach_cred: disabled\n");
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * _nfs4_proc_exchange_id()
  *
- * Since the clientid has expired, all compounds using sessions
- * associated with the stale clientid will be returning
- * NFS4ERR_BADSESSION in the sequence operation, and will therefore
- * be in some phase of session reset.
+ * Wrapper for EXCHANGE_ID operation.
  */
-int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
+static int _nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred,
+	u32 sp4_how)
 {
 	nfs4_verifier verifier;
 	struct nfs41_exchange_id_args args = {
@@ -5974,10 +6045,29 @@ int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
 		goto out_server_scope;
 	}
 
+	switch (sp4_how) {
+	case SP4_NONE:
+		args.state_protect.how = SP4_NONE;
+		break;
+
+	case SP4_MACH_CRED:
+		args.state_protect = nfs4_sp4_mach_cred_request;
+		break;
+
+	default:
+		/* unsupported! */
+		WARN_ON_ONCE(1);
+		status = -EINVAL;
+		goto out_server_scope;
+	}
+
 	status = rpc_call_sync(clp->cl_rpcclient, &msg, RPC_TASK_TIMEOUT);
 	if (status == 0)
 		status = nfs4_check_cl_exchange_flags(res.flags);
 
+	if (status == 0)
+		status = nfs4_sp4_select_mode(clp, &res.state_protect);
+
 	if (status == 0) {
 		clp->cl_clientid = res.clientid;
 		clp->cl_exchange_flags = (res.flags & ~EXCHGID4_FLAG_CONFIRMED_R);
@@ -6024,6 +6114,35 @@ out:
 	return status;
 }
 
+/*
+ * nfs4_proc_exchange_id()
+ *
+ * Returns zero, a negative errno, or a negative NFS4ERR status code.
+ *
+ * Since the clientid has expired, all compounds using sessions
+ * associated with the stale clientid will be returning
+ * NFS4ERR_BADSESSION in the sequence operation, and will therefore
+ * be in some phase of session reset.
+ *
+ * Will attempt to negotiate SP4_MACH_CRED if krb5i / krb5p auth is used.
+ */
+int nfs4_proc_exchange_id(struct nfs_client *clp, struct rpc_cred *cred)
+{
+	rpc_authflavor_t authflavor = clp->cl_rpcclient->cl_auth->au_flavor;
+	int status;
+
+	/* try SP4_MACH_CRED if krb5i/p	*/
+	if (authflavor == RPC_AUTH_GSS_KRB5I ||
+	    authflavor == RPC_AUTH_GSS_KRB5P) {
+		status = _nfs4_proc_exchange_id(clp, cred, SP4_MACH_CRED);
+		if (!status)
+			return 0;
+	}
+
+	/* try SP4_NONE */
+	return _nfs4_proc_exchange_id(clp, cred, SP4_NONE);
+}
+
 static int _nfs4_proc_destroy_clientid(struct nfs_client *clp,
 		struct rpc_cred *cred)
 {
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 1a4a3bd..9684354 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -294,7 +294,9 @@ static int nfs4_stat_to_errno(int);
 				XDR_QUADLEN(NFS4_EXCHANGE_ID_LEN) + \
 				1 /* flags */ + \
 				1 /* spa_how */ + \
-				0 /* SP4_NONE (for now) */ + \
+				/* max is SP4_MACH_CRED (for now) */ + \
+				1 + NFS4_OP_MAP_NUM_WORDS + \
+				1 + NFS4_OP_MAP_NUM_WORDS + \
 				1 /* implementation id array of size 1 */ + \
 				1 /* nii_domain */ + \
 				XDR_QUADLEN(NFS4_OPAQUE_LIMIT) + \
@@ -306,7 +308,9 @@ static int nfs4_stat_to_errno(int);
 				1 /* eir_sequenceid */ + \
 				1 /* eir_flags */ + \
 				1 /* spr_how */ + \
-				0 /* SP4_NONE (for now) */ + \
+				  /* max is SP4_MACH_CRED (for now) */ + \
+				1 + NFS4_OP_MAP_NUM_WORDS + \
+				1 + NFS4_OP_MAP_NUM_WORDS + \
 				2 /* eir_server_owner.so_minor_id */ + \
 				/* eir_server_owner.so_major_id<> */ \
 				XDR_QUADLEN(NFS4_OPAQUE_LIMIT) + 1 + \
@@ -1726,6 +1730,14 @@ static void encode_bind_conn_to_session(struct xdr_stream *xdr,
 	*p = 0;	/* use_conn_in_rdma_mode = False */
 }
 
+static void encode_op_map(struct xdr_stream *xdr, struct nfs4_op_map *op_map)
+{
+	unsigned int i;
+	encode_uint32(xdr, NFS4_OP_MAP_NUM_WORDS);
+	for (i = 0; i < NFS4_OP_MAP_NUM_WORDS; i++)
+		encode_uint32(xdr, op_map->u.words[i]);
+}
+
 static void encode_exchange_id(struct xdr_stream *xdr,
 			       struct nfs41_exchange_id_args *args,
 			       struct compound_hdr *hdr)
@@ -1739,9 +1751,20 @@ static void encode_exchange_id(struct xdr_stream *xdr,
 
 	encode_string(xdr, args->id_len, args->id);
 
-	p = reserve_space(xdr, 12);
-	*p++ = cpu_to_be32(args->flags);
-	*p++ = cpu_to_be32(0);	/* zero length state_protect4_a */
+	encode_uint32(xdr, args->flags);
+	encode_uint32(xdr, args->state_protect.how);
+
+	switch (args->state_protect.how) {
+	case SP4_NONE:
+		break;
+	case SP4_MACH_CRED:
+		encode_op_map(xdr, &args->state_protect.enforce);
+		encode_op_map(xdr, &args->state_protect.allow);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		break;
+	}
 
 	if (send_implementation_id &&
 	    sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN) > 1 &&
@@ -1752,7 +1775,7 @@ static void encode_exchange_id(struct xdr_stream *xdr,
 			       utsname()->version, utsname()->machine);
 
 	if (len > 0) {
-		*p = cpu_to_be32(1);	/* implementation id array length=1 */
+		encode_uint32(xdr, 1);	/* implementation id array length=1 */
 
 		encode_string(xdr,
 			sizeof(CONFIG_NFS_V4_1_IMPLEMENTATION_ID_DOMAIN) - 1,
@@ -1763,7 +1786,7 @@ static void encode_exchange_id(struct xdr_stream *xdr,
 		p = xdr_encode_hyper(p, 0);
 		*p = cpu_to_be32(0);
 	} else
-		*p = cpu_to_be32(0);	/* implementation id array length=0 */
+		encode_uint32(xdr, 0);	/* implementation id array length=0 */
 }
 
 static void encode_create_session(struct xdr_stream *xdr,
@@ -5375,6 +5398,23 @@ static int decode_secinfo_no_name(struct xdr_stream *xdr, struct nfs4_secinfo_re
 	return decode_secinfo_common(xdr, res);
 }
 
+static int decode_op_map(struct xdr_stream *xdr, struct nfs4_op_map *op_map)
+{
+	__be32 *p;
+	uint32_t bitmap_words;
+	unsigned int i;
+
+	p = xdr_inline_decode(xdr, 4);
+	bitmap_words = be32_to_cpup(p++);
+	if (bitmap_words > NFS4_OP_MAP_NUM_WORDS)
+		return -EIO;
+	p = xdr_inline_decode(xdr, 4 * bitmap_words);
+	for (i = 0; i < bitmap_words; i++)
+		op_map->u.words[i] = be32_to_cpup(p++);
+
+	return 0;
+}
+
 static int decode_exchange_id(struct xdr_stream *xdr,
 			      struct nfs41_exchange_id_res *res)
 {
@@ -5398,10 +5438,22 @@ static int decode_exchange_id(struct xdr_stream *xdr,
 	res->seqid = be32_to_cpup(p++);
 	res->flags = be32_to_cpup(p++);
 
-	/* We ask for SP4_NONE */
-	dummy = be32_to_cpup(p);
-	if (dummy != SP4_NONE)
+	res->state_protect.how = be32_to_cpup(p);
+	switch (res->state_protect.how) {
+	case SP4_NONE:
+		break;
+	case SP4_MACH_CRED:
+		status = decode_op_map(xdr, &res->state_protect.enforce);
+		if (status)
+			return status;
+		status = decode_op_map(xdr, &res->state_protect.allow);
+		if (status)
+			return status;
+		break;
+	default:
+		WARN_ON_ONCE(1);
 		return -EIO;
+	}
 
 	/* server_owner4.so_minor_id */
 	p = xdr_inline_decode(xdr, 8);
diff --git a/include/linux/nfs_fs_sb.h b/include/linux/nfs_fs_sb.h
index d221243..a0af429 100644
--- a/include/linux/nfs_fs_sb.h
+++ b/include/linux/nfs_fs_sb.h
@@ -87,6 +87,10 @@ struct nfs_client {
 	struct nfs41_server_owner *cl_serverowner;
 	struct nfs41_server_scope *cl_serverscope;
 	struct nfs41_impl_id	*cl_implid;
+	/* nfs 4.1+ state protection modes: */
+	unsigned long		cl_sp4_flags;
+#define NFS_SP4_MACH_CRED_MINIMAL  1	/* Minimal sp4_mach_cred - state ops
+					 * must use machine cred */
 #endif /* CONFIG_NFS_V4 */
 
 #ifdef CONFIG_NFS_FSCACHE
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index ddc3e32..b32f9d0 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -1107,6 +1107,23 @@ struct pnfs_ds_commit_info {
 	struct pnfs_commit_bucket *buckets;
 };
 
+#define NFS4_OP_MAP_NUM_LONGS \
+	DIV_ROUND_UP(LAST_NFS4_OP, 8 * sizeof(unsigned long))
+#define NFS4_OP_MAP_NUM_WORDS \
+	(NFS4_OP_MAP_NUM_LONGS * sizeof(unsigned long) / sizeof(u32))
+struct nfs4_op_map {
+	union {
+		unsigned long longs[NFS4_OP_MAP_NUM_LONGS];
+		u32 words[NFS4_OP_MAP_NUM_WORDS];
+	} u;
+};
+
+struct nfs41_state_protection {
+	u32 how;
+	struct nfs4_op_map enforce;
+	struct nfs4_op_map allow;
+};
+
 #define NFS4_EXCHANGE_ID_LEN	(48)
 struct nfs41_exchange_id_args {
 	struct nfs_client		*client;
@@ -1114,6 +1131,7 @@ struct nfs41_exchange_id_args {
 	unsigned int 			id_len;
 	char 				id[NFS4_EXCHANGE_ID_LEN];
 	u32				flags;
+	struct nfs41_state_protection	state_protect;
 };
 
 struct nfs41_server_owner {
@@ -1146,6 +1164,7 @@ struct nfs41_exchange_id_res {
 	struct nfs41_server_owner	*server_owner;
 	struct nfs41_server_scope	*server_scope;
 	struct nfs41_impl_id		*impl_id;
+	struct nfs41_state_protection	state_protect;
 };
 
 struct nfs41_create_session_args {
