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, 49 insertions, 0 deletions

diff --git a/include/net/netns/mctp.h b/include/net/netns/mctp.h
new file mode 100644
index 000000000..89555f90b
--- /dev/null
+++ b/include/net/netns/mctp.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * MCTP per-net structures
+ */
+
+#ifndef __NETNS_MCTP_H__
+#define __NETNS_MCTP_H__
+
+#include <linux/hash.h>
+#include <linux/hashtable.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+#define MCTP_BINDS_BITS 7
+
+struct netns_mctp {
+	/* Only updated under RTNL, entries freed via RCU */
+	struct list_head routes;
+
+	/* Bound sockets: hash table of sockets, keyed by
+	 * (type, src_eid, dest_eid).
+	 * Specific src_eid/dest_eid entries also have an entry for
+	 * MCTP_ADDR_ANY. This list is updated from non-atomic contexts
+	 * (under bind_lock), and read (under rcu) in packet rx.
+	 */
+	struct mutex bind_lock;
+	DECLARE_HASHTABLE(binds, MCTP_BINDS_BITS);
+
+	/* tag allocations. This list is read and updated from atomic contexts,
+	 * but elements are free()ed after a RCU grace-period
+	 */
+	spinlock_t keys_lock;
+	struct hlist_head keys;
+
+	/* MCTP network */
+	unsigned int default_net;
+
+	/* neighbour table */
+	struct mutex neigh_lock;
+	struct list_head neighbours;
+};
+
+static inline u32 mctp_bind_hash(u8 type, u8 local_addr, u8 peer_addr)
+{
+	return hash_32(type | (u32)local_addr << 8 | (u32)peer_addr << 16,
+		       MCTP_BINDS_BITS);
+}
+
+#endif /* __NETNS_MCTP_H__ */