KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 220 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-max8907.c b/drivers/rtc/rtc-max8907.c
new file mode 100644
index 000000000..af97140dd
--- /dev/null
+++ b/drivers/rtc/rtc-max8907.c
@@ -0,0 +1,220 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * RTC driver for Maxim MAX8907
+ *
+ * Copyright (c) 2011-2012, NVIDIA Corporation.
+ *
+ * Based on drivers/rtc/rtc-max8925.c,
+ * Copyright (C) 2009-2010 Marvell International Ltd.
+ */
+
+#include <linux/bcd.h>
+#include <linux/mfd/max8907.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rtc.h>
+#include <linux/slab.h>
+
+enum {
+	RTC_SEC = 0,
+	RTC_MIN,
+	RTC_HOUR,
+	RTC_WEEKDAY,
+	RTC_DATE,
+	RTC_MONTH,
+	RTC_YEAR1,
+	RTC_YEAR2,
+};
+
+#define TIME_NUM			8
+#define ALARM_1SEC			(1 << 7)
+#define HOUR_12				(1 << 7)
+#define HOUR_AM_PM			(1 << 5)
+#define ALARM0_IRQ			(1 << 3)
+#define ALARM1_IRQ			(1 << 2)
+#define ALARM0_STATUS			(1 << 2)
+#define ALARM1_STATUS			(1 << 1)
+
+struct max8907_rtc {
+	struct max8907		*max8907;
+	struct regmap		*regmap;
+	struct rtc_device	*rtc_dev;
+	int			irq;
+};
+
+static irqreturn_t max8907_irq_handler(int irq, void *data)
+{
+	struct max8907_rtc *rtc = data;
+
+	regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);
+
+	rtc_update_irq(rtc->rtc_dev, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static void regs_to_tm(u8 *regs, struct rtc_time *tm)
+{
+	tm->tm_year = bcd2bin(regs[RTC_YEAR2]) * 100 +
+		bcd2bin(regs[RTC_YEAR1]) - 1900;
+	tm->tm_mon = bcd2bin(regs[RTC_MONTH] & 0x1f) - 1;
+	tm->tm_mday = bcd2bin(regs[RTC_DATE] & 0x3f);
+	tm->tm_wday = (regs[RTC_WEEKDAY] & 0x07);
+	if (regs[RTC_HOUR] & HOUR_12) {
+		tm->tm_hour = bcd2bin(regs[RTC_HOUR] & 0x01f);
+		if (tm->tm_hour == 12)
+			tm->tm_hour = 0;
+		if (regs[RTC_HOUR] & HOUR_AM_PM)
+			tm->tm_hour += 12;
+	} else {
+		tm->tm_hour = bcd2bin(regs[RTC_HOUR] & 0x03f);
+	}
+	tm->tm_min = bcd2bin(regs[RTC_MIN] & 0x7f);
+	tm->tm_sec = bcd2bin(regs[RTC_SEC] & 0x7f);
+}
+
+static void tm_to_regs(struct rtc_time *tm, u8 *regs)
+{
+	u8 high, low;
+
+	high = (tm->tm_year + 1900) / 100;
+	low = tm->tm_year % 100;
+	regs[RTC_YEAR2] = bin2bcd(high);
+	regs[RTC_YEAR1] = bin2bcd(low);
+	regs[RTC_MONTH] = bin2bcd(tm->tm_mon + 1);
+	regs[RTC_DATE] = bin2bcd(tm->tm_mday);
+	regs[RTC_WEEKDAY] = tm->tm_wday;
+	regs[RTC_HOUR] = bin2bcd(tm->tm_hour);
+	regs[RTC_MIN] = bin2bcd(tm->tm_min);
+	regs[RTC_SEC] = bin2bcd(tm->tm_sec);
+}
+
+static int max8907_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	int ret;
+
+	ret = regmap_bulk_read(rtc->regmap, MAX8907_REG_RTC_SEC, regs,
+			       TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	regs_to_tm(regs, tm);
+
+	return 0;
+}
+
+static int max8907_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+
+	tm_to_regs(tm, regs);
+
+	return regmap_bulk_write(rtc->regmap, MAX8907_REG_RTC_SEC, regs,
+				 TIME_NUM);
+}
+
+static int max8907_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	unsigned int val;
+	int ret;
+
+	ret = regmap_bulk_read(rtc->regmap, MAX8907_REG_ALARM0_SEC, regs,
+			       TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	regs_to_tm(regs, &alrm->time);
+
+	ret = regmap_read(rtc->regmap, MAX8907_REG_ALARM0_CNTL, &val);
+	if (ret < 0)
+		return ret;
+
+	alrm->enabled = !!(val & 0x7f);
+
+	return 0;
+}
+
+static int max8907_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alrm)
+{
+	struct max8907_rtc *rtc = dev_get_drvdata(dev);
+	u8 regs[TIME_NUM];
+	int ret;
+
+	tm_to_regs(&alrm->time, regs);
+
+	/* Disable alarm while we update the target time */
+	ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0);
+	if (ret < 0)
+		return ret;
+
+	ret = regmap_bulk_write(rtc->regmap, MAX8907_REG_ALARM0_SEC, regs,
+				TIME_NUM);
+	if (ret < 0)
+		return ret;
+
+	if (alrm->enabled)
+		ret = regmap_write(rtc->regmap, MAX8907_REG_ALARM0_CNTL, 0x77);
+
+	return ret;
+}
+
+static const struct rtc_class_ops max8907_rtc_ops = {
+	.read_time	= max8907_rtc_read_time,
+	.set_time	= max8907_rtc_set_time,
+	.read_alarm	= max8907_rtc_read_alarm,
+	.set_alarm	= max8907_rtc_set_alarm,
+};
+
+static int max8907_rtc_probe(struct platform_device *pdev)
+{
+	struct max8907 *max8907 = dev_get_drvdata(pdev->dev.parent);
+	struct max8907_rtc *rtc;
+	int ret;
+
+	rtc = devm_kzalloc(&pdev->dev, sizeof(*rtc), GFP_KERNEL);
+	if (!rtc)
+		return -ENOMEM;
+	platform_set_drvdata(pdev, rtc);
+
+	rtc->max8907 = max8907;
+	rtc->regmap = max8907->regmap_rtc;
+
+	rtc->rtc_dev = devm_rtc_device_register(&pdev->dev, "max8907-rtc",
+					&max8907_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc->rtc_dev)) {
+		ret = PTR_ERR(rtc->rtc_dev);
+		dev_err(&pdev->dev, "Failed to register RTC device: %d\n", ret);
+		return ret;
+	}
+
+	rtc->irq = regmap_irq_get_virq(max8907->irqc_rtc,
+				       MAX8907_IRQ_RTC_ALARM0);
+	if (rtc->irq < 0)
+		return rtc->irq;
+
+	ret = devm_request_threaded_irq(&pdev->dev, rtc->irq, NULL,
+				max8907_irq_handler,
+				IRQF_ONESHOT, "max8907-alarm0", rtc);
+	if (ret < 0)
+		dev_err(&pdev->dev, "Failed to request IRQ%d: %d\n",
+			rtc->irq, ret);
+
+	return ret;
+}
+
+static struct platform_driver max8907_rtc_driver = {
+	.driver = {
+		.name = "max8907-rtc",
+	},
+	.probe = max8907_rtc_probe,
+};
+module_platform_driver(max8907_rtc_driver);
+
+MODULE_DESCRIPTION("Maxim MAX8907 RTC driver");
+MODULE_LICENSE("GPL v2");