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, 40 insertions, 0 deletions

diff --git a/include/rdma/frmr_pools.h b/include/rdma/frmr_pools.h
new file mode 100644
index 000000000..aed4d69d3
--- /dev/null
+++ b/include/rdma/frmr_pools.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
+ *
+ * Copyright (c) 2025, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+ */
+
+#ifndef FRMR_POOLS_H
+#define FRMR_POOLS_H
+
+#include <linux/types.h>
+#include <asm/page.h>
+
+struct ib_device;
+struct ib_mr;
+
+struct ib_frmr_key {
+	u64 vendor_key;
+	/* A pool with non-zero kernel_vendor_key is a kernel-only pool. */
+	u64 kernel_vendor_key;
+	size_t num_dma_blocks;
+	int access_flags;
+	u8 ats:1;
+};
+
+struct ib_frmr_pool_ops {
+	int (*create_frmrs)(struct ib_device *device, struct ib_frmr_key *key,
+			    u32 *handles, u32 count);
+	void (*destroy_frmrs)(struct ib_device *device, u32 *handles,
+			      u32 count);
+	int (*build_key)(struct ib_device *device, const struct ib_frmr_key *in,
+			 struct ib_frmr_key *out);
+};
+
+int ib_frmr_pools_init(struct ib_device *device,
+		       const struct ib_frmr_pool_ops *pool_ops);
+void ib_frmr_pools_cleanup(struct ib_device *device);
+int ib_frmr_pool_pop(struct ib_device *device, struct ib_mr *mr);
+void ib_frmr_pool_push(struct ib_device *device, struct ib_mr *mr);
+void ib_frmr_pool_drop(struct ib_mr *mr);
+
+#endif /* FRMR_POOLS_H */