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, 51 insertions, 0 deletions

diff --git a/include/sound/util_mem.h b/include/sound/util_mem.h
new file mode 100644
index 000000000..01310e089
--- /dev/null
+++ b/include/sound/util_mem.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_UTIL_MEM_H
+#define __SOUND_UTIL_MEM_H
+
+#include <linux/mutex.h>
+/*
+ *  Copyright (C) 2000 Takashi Iwai <tiwai@suse.de>
+ *
+ *  Generic memory management routines for soundcard memory allocation
+ */
+
+/*
+ * memory block
+ */
+struct snd_util_memblk {
+	unsigned int size;		/* size of this block */
+	unsigned int offset;		/* zero-offset of this block */
+	struct list_head list;		/* link */
+};
+
+#define snd_util_memblk_argptr(blk)	(void*)((char*)(blk) + sizeof(struct snd_util_memblk))
+
+/*
+ * memory management information
+ */
+struct snd_util_memhdr {
+	unsigned int size;		/* size of whole data */
+	struct list_head block;		/* block linked-list header */
+	int nblocks;			/* # of allocated blocks */
+	unsigned int used;		/* used memory size */
+	int block_extra_size;		/* extra data size of chunk */
+	struct mutex block_mutex;	/* lock */
+};
+
+/*
+ * prototypes
+ */
+struct snd_util_memhdr *snd_util_memhdr_new(int memsize);
+void snd_util_memhdr_free(struct snd_util_memhdr *hdr);
+struct snd_util_memblk *snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size);
+int snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk);
+int snd_util_mem_avail(struct snd_util_memhdr *hdr);
+
+/* functions without mutex */
+struct snd_util_memblk *__snd_util_mem_alloc(struct snd_util_memhdr *hdr, int size);
+void __snd_util_mem_free(struct snd_util_memhdr *hdr, struct snd_util_memblk *blk);
+struct snd_util_memblk *__snd_util_memblk_new(struct snd_util_memhdr *hdr,
+					      unsigned int units,
+					      struct list_head *prev);
+
+#endif /* __SOUND_UTIL_MEM_H */