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/drivers/gpio/gpiolib-shared.h b/drivers/gpio/gpiolib-shared.h
new file mode 100644
index 000000000..618756f6c
--- /dev/null
+++ b/drivers/gpio/gpiolib-shared.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __LINUX_GPIO_SHARED_H
+#define __LINUX_GPIO_SHARED_H
+
+#include <linux/mutex.h>
+
+struct gpio_device;
+struct gpio_desc;
+struct device;
+struct fwnode_handle;
+
+#if IS_ENABLED(CONFIG_GPIO_SHARED)
+
+int gpiochip_setup_shared(struct gpio_chip *gc);
+void gpio_device_teardown_shared(struct gpio_device *gdev);
+int gpio_shared_add_proxy_lookup(struct device *consumer,
+				 struct fwnode_handle *fwnode,
+				 const char *con_id, unsigned long lflags);
+
+#else
+
+static inline int gpiochip_setup_shared(struct gpio_chip *gc)
+{
+	return 0;
+}
+
+static inline void gpio_device_teardown_shared(struct gpio_device *gdev) { }
+
+static inline int gpio_shared_add_proxy_lookup(struct device *consumer,
+					       struct fwnode_handle *fwnode,
+					       const char *con_id,
+					       unsigned long lflags)
+{
+	return 0;
+}
+
+#endif /* CONFIG_GPIO_SHARED */
+
+struct gpio_shared_desc {
+	struct gpio_desc *desc;
+	unsigned long cfg;
+	unsigned int usecnt;
+	unsigned int votecnt;
+	int def_val;
+	struct mutex mutex; /* serializes all proxy operations on this descriptor */
+};
+
+struct gpio_shared_desc *devm_gpiod_shared_get(struct device *dev);
+
+#endif /* __LINUX_GPIO_SHARED_H */