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, 249 insertions, 0 deletions

diff --git a/drivers/acpi/ioapic.c b/drivers/acpi/ioapic.c
new file mode 100644
index 000000000..533ddd759
--- /dev/null
+++ b/drivers/acpi/ioapic.c
@@ -0,0 +1,249 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * IOAPIC/IOxAPIC/IOSAPIC driver
+ *
+ * Copyright (C) 2009 Fujitsu Limited.
+ * (c) Copyright 2009 Hewlett-Packard Development Company, L.P.
+ *
+ * Copyright (C) 2014 Intel Corporation
+ *
+ * Based on original drivers/pci/ioapic.c
+ *	Yinghai Lu <yinghai@kernel.org>
+ *	Jiang Liu <jiang.liu@intel.com>
+ */
+
+/*
+ * This driver manages I/O APICs added by hotplug after boot.
+ * We try to claim all I/O APIC devices, but those present at boot were
+ * registered when we parsed the ACPI MADT.
+ */
+
+#define pr_fmt(fmt) "ACPI: IOAPIC: " fmt
+
+#include <linux/slab.h>
+#include <linux/acpi.h>
+#include <linux/pci.h>
+#include <acpi/acpi.h>
+#include "internal.h"
+
+struct acpi_pci_ioapic {
+	acpi_handle	root_handle;
+	acpi_handle	handle;
+	u32		gsi_base;
+	struct resource	res;
+	struct pci_dev	*pdev;
+	struct list_head list;
+};
+
+static LIST_HEAD(ioapic_list);
+static DEFINE_MUTEX(ioapic_list_lock);
+
+static acpi_status setup_res(struct acpi_resource *acpi_res, void *data)
+{
+	struct resource *res = data;
+	struct resource_win win;
+
+	/*
+	 * We might assign this to 'res' later, make sure all pointers are
+	 * cleared before the resource is added to the global list
+	 */
+	memset(&win, 0, sizeof(win));
+
+	res->flags = 0;
+	if (acpi_dev_filter_resource_type(acpi_res, IORESOURCE_MEM))
+		return AE_OK;
+
+	if (!acpi_dev_resource_memory(acpi_res, res)) {
+		if (acpi_dev_resource_address_space(acpi_res, &win) ||
+		    acpi_dev_resource_ext_address_space(acpi_res, &win))
+			*res = win.res;
+	}
+	if ((res->flags & IORESOURCE_PREFETCH) ||
+	    (res->flags & IORESOURCE_DISABLED))
+		res->flags = 0;
+
+	return AE_CTRL_TERMINATE;
+}
+
+static bool acpi_is_ioapic(acpi_handle handle, char **type)
+{
+	acpi_status status;
+	struct acpi_device_info *info;
+	char *hid = NULL;
+	bool match = false;
+
+	if (!acpi_has_method(handle, "_GSB"))
+		return false;
+
+	status = acpi_get_object_info(handle, &info);
+	if (ACPI_SUCCESS(status)) {
+		if (info->valid & ACPI_VALID_HID)
+			hid = info->hardware_id.string;
+		if (hid) {
+			if (strcmp(hid, "ACPI0009") == 0) {
+				*type = "IOxAPIC";
+				match = true;
+			} else if (strcmp(hid, "ACPI000A") == 0) {
+				*type = "IOAPIC";
+				match = true;
+			}
+		}
+		kfree(info);
+	}
+
+	return match;
+}
+
+static acpi_status handle_ioapic_add(acpi_handle handle, u32 lvl,
+				     void *context, void **rv)
+{
+	acpi_status status;
+	unsigned long long gsi_base;
+	struct acpi_pci_ioapic *ioapic;
+	struct pci_dev *dev = NULL;
+	struct resource *res = NULL, *pci_res = NULL, *crs_res;
+	char *type = NULL;
+
+	if (!acpi_is_ioapic(handle, &type))
+		return AE_OK;
+
+	mutex_lock(&ioapic_list_lock);
+	list_for_each_entry(ioapic, &ioapic_list, list)
+		if (ioapic->handle == handle) {
+			mutex_unlock(&ioapic_list_lock);
+			return AE_OK;
+		}
+
+	status = acpi_evaluate_integer(handle, "_GSB", NULL, &gsi_base);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_warn(handle, "failed to evaluate _GSB method\n");
+		goto exit;
+	}
+
+	ioapic = kzalloc_obj(*ioapic);
+	if (!ioapic) {
+		pr_err("cannot allocate memory for new IOAPIC\n");
+		goto exit;
+	} else {
+		ioapic->root_handle = (acpi_handle)context;
+		ioapic->handle = handle;
+		ioapic->gsi_base = (u32)gsi_base;
+		INIT_LIST_HEAD(&ioapic->list);
+	}
+
+	if (acpi_ioapic_registered(handle, (u32)gsi_base))
+		goto done;
+
+	dev = acpi_get_pci_dev(handle);
+	if (dev && pci_resource_len(dev, 0)) {
+		if (pci_enable_device(dev) < 0)
+			goto exit_put;
+		pci_set_master(dev);
+		if (pci_request_region(dev, 0, type))
+			goto exit_disable;
+		pci_res = &dev->resource[0];
+		ioapic->pdev = dev;
+	} else {
+		pci_dev_put(dev);
+		dev = NULL;
+	}
+
+	crs_res = &ioapic->res;
+	acpi_walk_resources(handle, METHOD_NAME__CRS, setup_res, crs_res);
+	crs_res->name = type;
+	crs_res->flags |= IORESOURCE_BUSY;
+	if (crs_res->flags == 0) {
+		acpi_handle_warn(handle, "failed to get resource\n");
+		goto exit_release;
+	} else if (insert_resource(&iomem_resource, crs_res)) {
+		acpi_handle_warn(handle, "failed to insert resource\n");
+		goto exit_release;
+	}
+
+	/* try pci resource first, then "_CRS" resource */
+	res = pci_res;
+	if (!res || !res->flags)
+		res = crs_res;
+
+	if (acpi_register_ioapic(handle, res->start, (u32)gsi_base)) {
+		acpi_handle_warn(handle, "failed to register IOAPIC\n");
+		goto exit_release;
+	}
+done:
+	list_add(&ioapic->list, &ioapic_list);
+	mutex_unlock(&ioapic_list_lock);
+
+	if (dev)
+		dev_info(&dev->dev, "%s at %pR, GSI %u\n",
+			 type, res, (u32)gsi_base);
+	else
+		acpi_handle_info(handle, "%s at %pR, GSI %u\n",
+				 type, res, (u32)gsi_base);
+
+	return AE_OK;
+
+exit_release:
+	if (dev)
+		pci_release_region(dev, 0);
+	if (ioapic->res.flags && ioapic->res.parent)
+		release_resource(&ioapic->res);
+exit_disable:
+	if (dev)
+		pci_disable_device(dev);
+exit_put:
+	pci_dev_put(dev);
+	kfree(ioapic);
+exit:
+	mutex_unlock(&ioapic_list_lock);
+	*(acpi_status *)rv = AE_ERROR;
+	return AE_OK;
+}
+
+int acpi_ioapic_add(acpi_handle root_handle)
+{
+	acpi_status status, retval = AE_OK;
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, root_handle,
+				     UINT_MAX, handle_ioapic_add, NULL,
+				     root_handle, (void **)&retval);
+
+	return ACPI_SUCCESS(status) && ACPI_SUCCESS(retval) ? 0 : -ENODEV;
+}
+
+void pci_ioapic_remove(struct acpi_pci_root *root)
+{
+	struct acpi_pci_ioapic *ioapic, *tmp;
+
+	mutex_lock(&ioapic_list_lock);
+	list_for_each_entry_safe(ioapic, tmp, &ioapic_list, list) {
+		if (root->device->handle != ioapic->root_handle)
+			continue;
+		if (ioapic->pdev) {
+			pci_release_region(ioapic->pdev, 0);
+			pci_disable_device(ioapic->pdev);
+			pci_dev_put(ioapic->pdev);
+		}
+	}
+	mutex_unlock(&ioapic_list_lock);
+}
+
+int acpi_ioapic_remove(struct acpi_pci_root *root)
+{
+	int retval = 0;
+	struct acpi_pci_ioapic *ioapic, *tmp;
+
+	mutex_lock(&ioapic_list_lock);
+	list_for_each_entry_safe(ioapic, tmp, &ioapic_list, list) {
+		if (root->device->handle != ioapic->root_handle)
+			continue;
+		if (acpi_unregister_ioapic(ioapic->handle, ioapic->gsi_base))
+			retval = -EBUSY;
+		if (ioapic->res.flags && ioapic->res.parent)
+			release_resource(&ioapic->res);
+		list_del(&ioapic->list);
+		kfree(ioapic);
+	}
+	mutex_unlock(&ioapic_list_lock);
+
+	return retval;
+}