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, 75 insertions, 0 deletions

diff --git a/include/sound/pcm_oss.h b/include/sound/pcm_oss.h
new file mode 100644
index 000000000..c96f23c77
--- /dev/null
+++ b/include/sound/pcm_oss.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+#ifndef __SOUND_PCM_OSS_H
+#define __SOUND_PCM_OSS_H
+
+/*
+ *  Digital Audio (PCM) - OSS compatibility abstract layer
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+struct snd_pcm_oss_setup {
+	char *task_name;
+	unsigned int disable:1,
+		     direct:1,
+		     block:1,
+		     nonblock:1,
+		     partialfrag:1,
+		     nosilence:1,
+		     buggyptr:1;
+	unsigned int periods;
+	unsigned int period_size;
+	struct snd_pcm_oss_setup *next;
+};
+
+struct snd_pcm_oss_runtime {
+	unsigned params: 1,			/* format/parameter change */
+		 prepare: 1,			/* need to prepare the operation */
+		 trigger: 1,			/* trigger flag */
+		 sync_trigger: 1;		/* sync trigger flag */
+	int rate;				/* requested rate */
+	int format;				/* requested OSS format */
+	unsigned int channels;			/* requested channels */
+	unsigned int fragshift;
+	unsigned int maxfrags;
+	unsigned int subdivision;		/* requested subdivision */
+	size_t period_bytes;			/* requested period size */
+	size_t period_frames;			/* period frames for poll */
+	size_t period_ptr;			/* actual write pointer to period */
+	unsigned int periods;
+	size_t buffer_bytes;			/* requested buffer size */
+	size_t bytes;				/* total # bytes processed */
+	size_t mmap_bytes;
+	char *buffer;				/* vmallocated period */
+	size_t buffer_used;			/* used length from period buffer */
+	struct mutex params_lock;
+	atomic_t rw_ref;		/* concurrent read/write accesses */
+#ifdef CONFIG_SND_PCM_OSS_PLUGINS
+	struct snd_pcm_plugin *plugin_first;
+	struct snd_pcm_plugin *plugin_last;
+#endif
+	unsigned int prev_hw_ptr_period;
+};
+
+struct snd_pcm_oss_file {
+	struct snd_pcm_substream *streams[2];
+};
+
+struct snd_pcm_oss_substream {
+	unsigned oss: 1;			/* oss mode */
+	struct snd_pcm_oss_setup setup;		/* active setup */
+};
+
+struct snd_pcm_oss_stream {
+	struct snd_pcm_oss_setup *setup_list;	/* setup list */
+	struct mutex setup_mutex;
+#ifdef CONFIG_SND_VERBOSE_PROCFS
+	struct snd_info_entry *proc_entry;
+#endif
+};
+
+struct snd_pcm_oss {
+	int reg;
+	unsigned int reg_mask;
+};
+
+#endif /* __SOUND_PCM_OSS_H */