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, 63 insertions, 0 deletions

diff --git a/drivers/misc/sram.h b/drivers/misc/sram.h
new file mode 100644
index 000000000..397205b8b
--- /dev/null
+++ b/drivers/misc/sram.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Defines for the SRAM driver
+ */
+#ifndef __SRAM_H
+#define __SRAM_H
+
+struct sram_config {
+	int (*init)(void);
+	bool map_only_reserved;
+};
+
+struct sram_partition {
+	void __iomem *base;
+
+	struct gen_pool *pool;
+	struct bin_attribute battr;
+	struct mutex lock;
+	struct list_head list;
+};
+
+struct sram_dev {
+	const struct sram_config *config;
+
+	struct device *dev;
+	void __iomem *virt_base;
+	bool no_memory_wc;
+
+	struct gen_pool *pool;
+
+	struct sram_partition *partition;
+	u32 partitions;
+};
+
+struct sram_reserve {
+	struct list_head list;
+	u32 start;
+	u32 size;
+	struct resource res;
+	bool export;
+	bool pool;
+	bool protect_exec;
+	const char *label;
+};
+
+#ifdef CONFIG_SRAM_EXEC
+int sram_check_protect_exec(struct sram_dev *sram, struct sram_reserve *block,
+			    struct sram_partition *part);
+int sram_add_protect_exec(struct sram_partition *part);
+#else
+static inline int sram_check_protect_exec(struct sram_dev *sram,
+					  struct sram_reserve *block,
+					  struct sram_partition *part)
+{
+	return -ENODEV;
+}
+
+static inline int sram_add_protect_exec(struct sram_partition *part)
+{
+	return -ENODEV;
+}
+#endif /* CONFIG_SRAM_EXEC */
+#endif /* __SRAM_H */