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, 130 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-aspeed.c b/drivers/rtc/rtc-aspeed.c
new file mode 100644
index 000000000..8f5b440f8
--- /dev/null
+++ b/drivers/rtc/rtc-aspeed.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0+
+// Copyright 2015 IBM Corp.
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/rtc.h>
+#include <linux/io.h>
+
+struct aspeed_rtc {
+	void __iomem *base;
+};
+
+#define RTC_TIME	0x00
+#define RTC_YEAR	0x04
+#define RTC_CTRL	0x10
+
+#define RTC_UNLOCK	BIT(1)
+#define RTC_ENABLE	BIT(0)
+
+static int aspeed_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct aspeed_rtc *rtc = dev_get_drvdata(dev);
+	unsigned int cent, year;
+	u32 reg1, reg2;
+
+	if (!(readl(rtc->base + RTC_CTRL) & RTC_ENABLE)) {
+		dev_dbg(dev, "%s failing as rtc disabled\n", __func__);
+		return -EINVAL;
+	}
+
+	do {
+		reg2 = readl(rtc->base + RTC_YEAR);
+		reg1 = readl(rtc->base + RTC_TIME);
+	} while (reg2 != readl(rtc->base + RTC_YEAR));
+
+	tm->tm_mday = (reg1 >> 24) & 0x1f;
+	tm->tm_hour = (reg1 >> 16) & 0x1f;
+	tm->tm_min = (reg1 >> 8) & 0x3f;
+	tm->tm_sec = (reg1 >> 0) & 0x3f;
+
+	cent = (reg2 >> 16) & 0x1f;
+	year = (reg2 >> 8) & 0x7f;
+	tm->tm_mon = ((reg2 >>  0) & 0x0f) - 1;
+	tm->tm_year = year + (cent * 100) - 1900;
+
+	dev_dbg(dev, "%s %ptR", __func__, tm);
+
+	return 0;
+}
+
+static int aspeed_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct aspeed_rtc *rtc = dev_get_drvdata(dev);
+	u32 reg1, reg2, ctrl;
+	int year, cent;
+
+	cent = (tm->tm_year + 1900) / 100;
+	year = tm->tm_year % 100;
+
+	reg1 = (tm->tm_mday << 24) | (tm->tm_hour << 16) | (tm->tm_min << 8) |
+		tm->tm_sec;
+
+	reg2 = ((cent & 0x1f) << 16) | ((year & 0x7f) << 8) |
+		((tm->tm_mon + 1) & 0xf);
+
+	ctrl = readl(rtc->base + RTC_CTRL);
+	writel(ctrl | RTC_UNLOCK, rtc->base + RTC_CTRL);
+
+	writel(reg1, rtc->base + RTC_TIME);
+	writel(reg2, rtc->base + RTC_YEAR);
+
+	/* Re-lock and ensure enable is set now that a time is programmed */
+	writel(ctrl | RTC_ENABLE, rtc->base + RTC_CTRL);
+
+	return 0;
+}
+
+static const struct rtc_class_ops aspeed_rtc_ops = {
+	.read_time = aspeed_rtc_read_time,
+	.set_time = aspeed_rtc_set_time,
+};
+
+static int aspeed_rtc_probe(struct platform_device *pdev)
+{
+	struct aspeed_rtc *rtc;
+	struct rtc_device *rtc_dev;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+
+	rtc->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(rtc->base))
+		return PTR_ERR(rtc->base);
+
+	rtc_dev = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(rtc_dev))
+		return PTR_ERR(rtc_dev);
+
+	platform_set_drvdata(pdev, rtc);
+
+	rtc_dev->ops = &aspeed_rtc_ops;
+	rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_1900;
+	rtc_dev->range_max = 38814989399LL; /* 3199-12-31 23:59:59 */
+
+	return devm_rtc_register_device(rtc_dev);
+}
+
+static const struct of_device_id aspeed_rtc_match[] = {
+	{ .compatible = "aspeed,ast2400-rtc", },
+	{ .compatible = "aspeed,ast2500-rtc", },
+	{ .compatible = "aspeed,ast2600-rtc", },
+	{ .compatible = "aspeed,ast2700-rtc", },
+	{}
+};
+MODULE_DEVICE_TABLE(of, aspeed_rtc_match);
+
+static struct platform_driver aspeed_rtc_driver = {
+	.driver = {
+		.name = "aspeed-rtc",
+		.of_match_table = aspeed_rtc_match,
+	},
+};
+
+module_platform_driver_probe(aspeed_rtc_driver, aspeed_rtc_probe);
+
+MODULE_DESCRIPTION("ASPEED RTC driver");
+MODULE_AUTHOR("Joel Stanley <joel@jms.id.au>");
+MODULE_LICENSE("GPL");