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, 85 insertions, 0 deletions

diff --git a/include/drm/drm_accel.h b/include/drm/drm_accel.h
new file mode 100644
index 000000000..20a665ec6
--- /dev/null
+++ b/include/drm/drm_accel.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright 2022 HabanaLabs, Ltd.
+ * All Rights Reserved.
+ *
+ */
+
+#ifndef DRM_ACCEL_H_
+#define DRM_ACCEL_H_
+
+#include <drm/drm_file.h>
+
+#define ACCEL_MAJOR		261
+#define ACCEL_MAX_MINORS	256
+
+/**
+ * DRM_ACCEL_FOPS - Default drm accelerators file operations
+ *
+ * This macro provides a shorthand for setting the accelerator file ops in the
+ * &file_operations structure.  If all you need are the default ops, use
+ * DEFINE_DRM_ACCEL_FOPS instead.
+ */
+#define DRM_ACCEL_FOPS \
+	.open		= accel_open,\
+	.release	= drm_release,\
+	.unlocked_ioctl	= drm_ioctl,\
+	.compat_ioctl	= drm_compat_ioctl,\
+	.poll		= drm_poll,\
+	.read		= drm_read,\
+	.llseek		= noop_llseek, \
+	.mmap		= drm_gem_mmap, \
+	.fop_flags	= FOP_UNSIGNED_OFFSET
+
+/**
+ * DEFINE_DRM_ACCEL_FOPS() - macro to generate file operations for accelerators drivers
+ * @name: name for the generated structure
+ *
+ * This macro autogenerates a suitable &struct file_operations for accelerators based
+ * drivers, which can be assigned to &drm_driver.fops. Note that this structure
+ * cannot be shared between drivers, because it contains a reference to the
+ * current module using THIS_MODULE.
+ *
+ * Note that the declaration is already marked as static - if you need a
+ * non-static version of this you're probably doing it wrong and will break the
+ * THIS_MODULE reference by accident.
+ */
+#define DEFINE_DRM_ACCEL_FOPS(name) \
+	static const struct file_operations name = {\
+		.owner		= THIS_MODULE,\
+		DRM_ACCEL_FOPS,\
+	}
+
+#if IS_ENABLED(CONFIG_DRM_ACCEL)
+
+extern struct xarray accel_minors_xa;
+
+void accel_core_exit(void);
+int accel_core_init(void);
+void accel_set_device_instance_params(struct device *kdev, int index);
+int accel_open(struct inode *inode, struct file *filp);
+void accel_debugfs_register(struct drm_device *dev);
+
+#else
+
+static inline void accel_core_exit(void)
+{
+}
+
+static inline int __init accel_core_init(void)
+{
+	/* Return 0 to allow drm_core_init to complete successfully */
+	return 0;
+}
+
+static inline void accel_set_device_instance_params(struct device *kdev, int index)
+{
+}
+
+static inline void accel_debugfs_register(struct drm_device *dev)
+{
+}
+
+#endif /* IS_ENABLED(CONFIG_DRM_ACCEL) */
+
+#endif /* DRM_ACCEL_H_ */