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, 184 insertions, 0 deletions

diff --git a/drivers/mtd/hyperbus/rpc-if.c b/drivers/mtd/hyperbus/rpc-if.c
new file mode 100644
index 000000000..f448e23f9
--- /dev/null
+++ b/drivers/mtd/hyperbus/rpc-if.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Linux driver for RPC-IF HyperFlash
+ *
+ * Copyright (C) 2019-2020 Cogent Embedded, Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mtd/hyperbus.h>
+#include <linux/mtd/mtd.h>
+#include <linux/mux/consumer.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/types.h>
+
+#include <memory/renesas-rpc-if.h>
+
+struct	rpcif_hyperbus {
+	struct rpcif rpc;
+	struct hyperbus_ctlr ctlr;
+	struct hyperbus_device hbdev;
+};
+
+static const struct rpcif_op rpcif_op_tmpl = {
+	.cmd = {
+		.buswidth = 8,
+		.ddr = true,
+	},
+	.ocmd = {
+		.buswidth = 8,
+		.ddr = true,
+	},
+	.addr = {
+		.nbytes = 1,
+		.buswidth = 8,
+		.ddr = true,
+	},
+	.data = {
+		.buswidth = 8,
+		.ddr = true,
+	},
+};
+
+static void rpcif_hb_prepare_read(struct rpcif *rpc, void *to,
+				  unsigned long from, ssize_t len)
+{
+	struct rpcif_op op = rpcif_op_tmpl;
+
+	op.cmd.opcode = HYPERBUS_RW_READ | HYPERBUS_AS_MEM;
+	op.addr.val = from >> 1;
+	op.dummy.buswidth = 1;
+	op.dummy.ncycles = 15;
+	op.data.dir = RPCIF_DATA_IN;
+	op.data.nbytes = len;
+	op.data.buf.in = to;
+
+	rpcif_prepare(rpc->dev, &op, NULL, NULL);
+}
+
+static void rpcif_hb_prepare_write(struct rpcif *rpc, unsigned long to,
+				   void *from, ssize_t len)
+{
+	struct rpcif_op op = rpcif_op_tmpl;
+
+	op.cmd.opcode = HYPERBUS_RW_WRITE | HYPERBUS_AS_MEM;
+	op.addr.val = to >> 1;
+	op.data.dir = RPCIF_DATA_OUT;
+	op.data.nbytes = len;
+	op.data.buf.out = from;
+
+	rpcif_prepare(rpc->dev, &op, NULL, NULL);
+}
+
+static u16 rpcif_hb_read16(struct hyperbus_device *hbdev, unsigned long addr)
+{
+	struct rpcif_hyperbus *hyperbus =
+		container_of(hbdev, struct rpcif_hyperbus, hbdev);
+	map_word data;
+
+	rpcif_hb_prepare_read(&hyperbus->rpc, &data, addr, 2);
+
+	rpcif_manual_xfer(hyperbus->rpc.dev);
+
+	return data.x[0];
+}
+
+static void rpcif_hb_write16(struct hyperbus_device *hbdev, unsigned long addr,
+			     u16 data)
+{
+	struct rpcif_hyperbus *hyperbus =
+		container_of(hbdev, struct rpcif_hyperbus, hbdev);
+
+	rpcif_hb_prepare_write(&hyperbus->rpc, addr, &data, 2);
+
+	rpcif_manual_xfer(hyperbus->rpc.dev);
+}
+
+static void rpcif_hb_copy_from(struct hyperbus_device *hbdev, void *to,
+			       unsigned long from, ssize_t len)
+{
+	struct rpcif_hyperbus *hyperbus =
+		container_of(hbdev, struct rpcif_hyperbus, hbdev);
+
+	rpcif_hb_prepare_read(&hyperbus->rpc, to, from, len);
+
+	rpcif_dirmap_read(hyperbus->rpc.dev, from, len, to);
+}
+
+static const struct hyperbus_ops rpcif_hb_ops = {
+	.read16 = rpcif_hb_read16,
+	.write16 = rpcif_hb_write16,
+	.copy_from = rpcif_hb_copy_from,
+};
+
+static int rpcif_hb_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rpcif_hyperbus *hyperbus;
+	int error;
+
+	hyperbus = devm_kzalloc(dev, sizeof(*hyperbus), GFP_KERNEL);
+	if (!hyperbus)
+		return -ENOMEM;
+
+	error = rpcif_sw_init(&hyperbus->rpc, pdev->dev.parent);
+	if (error)
+		return error;
+
+	platform_set_drvdata(pdev, hyperbus);
+
+	pm_runtime_enable(hyperbus->rpc.dev);
+
+	error = rpcif_hw_init(hyperbus->rpc.dev, true);
+	if (error)
+		goto out_disable_rpm;
+
+	hyperbus->hbdev.map.size = hyperbus->rpc.size;
+	hyperbus->hbdev.map.virt = hyperbus->rpc.dirmap;
+
+	hyperbus->ctlr.dev = dev;
+	hyperbus->ctlr.ops = &rpcif_hb_ops;
+	hyperbus->hbdev.ctlr = &hyperbus->ctlr;
+	hyperbus->hbdev.np = of_get_next_child(pdev->dev.parent->of_node, NULL);
+	error = hyperbus_register_device(&hyperbus->hbdev);
+	if (error)
+		goto out_disable_rpm;
+
+	return 0;
+
+out_disable_rpm:
+	pm_runtime_disable(hyperbus->rpc.dev);
+	return error;
+}
+
+static void rpcif_hb_remove(struct platform_device *pdev)
+{
+	struct rpcif_hyperbus *hyperbus = platform_get_drvdata(pdev);
+
+	hyperbus_unregister_device(&hyperbus->hbdev);
+
+	pm_runtime_disable(hyperbus->rpc.dev);
+}
+
+static const struct platform_device_id rpc_if_hyperflash_id_table[] = {
+	{ .name = "rpc-if-hyperflash" },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, rpc_if_hyperflash_id_table);
+
+static struct platform_driver rpcif_platform_driver = {
+	.probe	= rpcif_hb_probe,
+	.remove = rpcif_hb_remove,
+	.id_table = rpc_if_hyperflash_id_table,
+	.driver	= {
+		.name	= "rpc-if-hyperflash",
+	},
+};
+
+module_platform_driver(rpcif_platform_driver);
+
+MODULE_DESCRIPTION("Renesas RPC-IF HyperFlash driver");
+MODULE_LICENSE("GPL v2");