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, 267 insertions, 0 deletions

diff --git a/drivers/nvmem/brcm_nvram.c b/drivers/nvmem/brcm_nvram.c
new file mode 100644
index 000000000..9f77aee37
--- /dev/null
+++ b/drivers/nvmem/brcm_nvram.c
@@ -0,0 +1,267 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Rafał Miłecki <rafal@milecki.pl>
+ */
+
+#include <linux/bcm47xx_nvram.h>
+#include <linux/etherdevice.h>
+#include <linux/hex.h>
+#include <linux/if_ether.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/nvmem-provider.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#define NVRAM_MAGIC			"FLSH"
+
+/**
+ * struct brcm_nvram - driver state internal struct
+ *
+ * @dev:		NVMEM device pointer
+ * @nvmem_size:		Size of the whole space available for NVRAM
+ * @data:		NVRAM data copy stored to avoid poking underlying flash controller
+ * @data_len:		NVRAM data size
+ * @padding_byte:	Padding value used to fill remaining space
+ * @cells:		Array of discovered NVMEM cells
+ * @ncells:		Number of elements in cells
+ */
+struct brcm_nvram {
+	struct device *dev;
+	size_t nvmem_size;
+	uint8_t *data;
+	size_t data_len;
+	uint8_t padding_byte;
+	struct nvmem_cell_info *cells;
+	int ncells;
+};
+
+struct brcm_nvram_header {
+	char magic[4];
+	__le32 len;
+	__le32 crc_ver_init;	/* 0:7 crc, 8:15 ver, 16:31 sdram_init */
+	__le32 config_refresh;	/* 0:15 sdram_config, 16:31 sdram_refresh */
+	__le32 config_ncdl;	/* ncdl values for memc */
+};
+
+static int brcm_nvram_read(void *context, unsigned int offset, void *val,
+			   size_t bytes)
+{
+	struct brcm_nvram *priv = context;
+	size_t to_copy;
+
+	if (offset + bytes > priv->data_len)
+		to_copy = max_t(ssize_t, (ssize_t)priv->data_len - offset, 0);
+	else
+		to_copy = bytes;
+
+	memcpy(val, priv->data + offset, to_copy);
+
+	memset((uint8_t *)val + to_copy, priv->padding_byte, bytes - to_copy);
+
+	return 0;
+}
+
+static int brcm_nvram_copy_data(struct brcm_nvram *priv, struct platform_device *pdev)
+{
+	struct resource *res;
+	void __iomem *base;
+
+	base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	priv->nvmem_size = resource_size(res);
+
+	priv->padding_byte = readb(base + priv->nvmem_size - 1);
+	for (priv->data_len = priv->nvmem_size;
+	     priv->data_len;
+	     priv->data_len--) {
+		if (readb(base + priv->data_len - 1) != priv->padding_byte)
+			break;
+	}
+	WARN(priv->data_len > SZ_128K, "Unexpected (big) NVRAM size: %zu B\n", priv->data_len);
+
+	if (priv->data_len < sizeof(struct brcm_nvram_header)) {
+		dev_err(priv->dev, "NVRAM data too small (%zu)\n", priv->data_len);
+		return -EINVAL;
+	}
+
+	priv->data = devm_kzalloc(priv->dev, priv->data_len, GFP_KERNEL);
+	if (!priv->data)
+		return -ENOMEM;
+
+	memcpy_fromio(priv->data, base, priv->data_len);
+
+	bcm47xx_nvram_init_from_iomem(base, priv->data_len);
+
+	return 0;
+}
+
+static int brcm_nvram_read_post_process_macaddr(void *context, const char *id, int index,
+						unsigned int offset, void *buf, size_t bytes)
+{
+	u8 mac[ETH_ALEN];
+
+	if (bytes != MAC_ADDR_STR_LEN)
+		return -EINVAL;
+
+	if (!mac_pton(buf, mac))
+		return -EINVAL;
+
+	if (index)
+		eth_addr_add(mac, index);
+
+	ether_addr_copy(buf, mac);
+
+	return 0;
+}
+
+static int brcm_nvram_add_cells(struct brcm_nvram *priv, uint8_t *data,
+				size_t len)
+{
+	struct device *dev = priv->dev;
+	char *var, *value;
+	uint8_t tmp;
+	int idx;
+	int err = 0;
+
+	tmp = priv->data[len - 1];
+	priv->data[len - 1] = '\0';
+
+	priv->ncells = 0;
+	for (var = data + sizeof(struct brcm_nvram_header);
+	     var < (char *)data + len && *var;
+	     var += strlen(var) + 1) {
+		priv->ncells++;
+	}
+
+	priv->cells = devm_kcalloc(dev, priv->ncells, sizeof(*priv->cells), GFP_KERNEL);
+	if (!priv->cells) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	for (var = data + sizeof(struct brcm_nvram_header), idx = 0;
+	     var < (char *)data + len && *var;
+	     var = value + strlen(value) + 1, idx++) {
+		char *eq, *name;
+
+		eq = strchr(var, '=');
+		if (!eq)
+			break;
+		*eq = '\0';
+		name = devm_kstrdup(dev, var, GFP_KERNEL);
+		*eq = '=';
+		if (!name) {
+			err = -ENOMEM;
+			goto out;
+		}
+		value = eq + 1;
+
+		priv->cells[idx].name = name;
+		priv->cells[idx].offset = value - (char *)data;
+		priv->cells[idx].bytes = strlen(value);
+		priv->cells[idx].np = of_get_child_by_name(dev->of_node, priv->cells[idx].name);
+		if (!strcmp(name, "et0macaddr") ||
+		    !strcmp(name, "et1macaddr") ||
+		    !strcmp(name, "et2macaddr")) {
+			priv->cells[idx].raw_len = strlen(value);
+			priv->cells[idx].bytes = ETH_ALEN;
+			priv->cells[idx].read_post_process = brcm_nvram_read_post_process_macaddr;
+		}
+	}
+
+out:
+	priv->data[len - 1] = tmp;
+	return err;
+}
+
+static int brcm_nvram_parse(struct brcm_nvram *priv)
+{
+	struct brcm_nvram_header *header = (struct brcm_nvram_header *)priv->data;
+	struct device *dev = priv->dev;
+	size_t len;
+	int err;
+
+	if (memcmp(header->magic, NVRAM_MAGIC, 4)) {
+		dev_err(dev, "Invalid NVRAM magic\n");
+		return -EINVAL;
+	}
+
+	len = le32_to_cpu(header->len);
+	if (len < sizeof(*header)) {
+		dev_err(dev, "NVRAM length (%zd) too small\n", len);
+		return -EINVAL;
+	}
+	if (len > priv->data_len) {
+		dev_err(dev, "NVRAM length (%zd) exceeds data size (%zd)\n", len,
+			priv->data_len);
+		return -EINVAL;
+	}
+
+	err = brcm_nvram_add_cells(priv, priv->data, len);
+	if (err)
+		dev_err(dev, "Failed to add cells: %d\n", err);
+
+	return 0;
+}
+
+static int brcm_nvram_probe(struct platform_device *pdev)
+{
+	struct nvmem_config config = {
+		.name = "brcm-nvram",
+		.reg_read = brcm_nvram_read,
+	};
+	struct device *dev = &pdev->dev;
+	struct brcm_nvram *priv;
+	int err;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	priv->dev = dev;
+
+	err = brcm_nvram_copy_data(priv, pdev);
+	if (err)
+		return err;
+
+	err = brcm_nvram_parse(priv);
+	if (err)
+		return err;
+
+	config.dev = dev;
+	config.cells = priv->cells;
+	config.ncells = priv->ncells;
+	config.priv = priv;
+	config.size = priv->nvmem_size;
+
+	return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config));
+}
+
+static const struct of_device_id brcm_nvram_of_match_table[] = {
+	{ .compatible = "brcm,nvram", },
+	{},
+};
+
+static struct platform_driver brcm_nvram_driver = {
+	.probe = brcm_nvram_probe,
+	.driver = {
+		.name = "brcm_nvram",
+		.of_match_table = brcm_nvram_of_match_table,
+	},
+};
+
+static int __init brcm_nvram_init(void)
+{
+	return platform_driver_register(&brcm_nvram_driver);
+}
+
+subsys_initcall_sync(brcm_nvram_init);
+
+MODULE_AUTHOR("Rafał Miłecki");
+MODULE_DESCRIPTION("Broadcom I/O-mapped NVRAM support driver");
+MODULE_LICENSE("GPL");
+MODULE_DEVICE_TABLE(of, brcm_nvram_of_match_table);