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, 349 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-mc13xxx.c b/drivers/rtc/rtc-mc13xxx.c
new file mode 100644
index 000000000..7960d5fa8
--- /dev/null
+++ b/drivers/rtc/rtc-mc13xxx.c
@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Real Time Clock driver for Freescale MC13XXX PMIC
+ *
+ * (C) 2009 Sascha Hauer, Pengutronix
+ * (C) 2009 Uwe Kleine-Koenig, Pengutronix
+ */
+
+#include <linux/mfd/mc13xxx.h>
+#include <linux/platform_device.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/rtc.h>
+
+#define DRIVER_NAME "mc13xxx-rtc"
+
+#define MC13XXX_RTCTOD	20
+#define MC13XXX_RTCTODA	21
+#define MC13XXX_RTCDAY	22
+#define MC13XXX_RTCDAYA	23
+
+#define SEC_PER_DAY	(24 * 60 * 60)
+
+struct mc13xxx_rtc {
+	struct rtc_device *rtc;
+	struct mc13xxx *mc13xxx;
+	int valid;
+};
+
+static int mc13xxx_rtc_irq_enable_unlocked(struct device *dev,
+		unsigned int enabled, int irq)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	int (*func)(struct mc13xxx *mc13xxx, int irq);
+
+	if (!priv->valid)
+		return -ENODATA;
+
+	func = enabled ? mc13xxx_irq_unmask : mc13xxx_irq_mask;
+	return func(priv->mc13xxx, irq);
+}
+
+static int mc13xxx_rtc_alarm_irq_enable(struct device *dev,
+					unsigned int enabled)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	int ret;
+
+	mc13xxx_lock(priv->mc13xxx);
+
+	ret = mc13xxx_rtc_irq_enable_unlocked(dev, enabled, MC13XXX_IRQ_TODA);
+
+	mc13xxx_unlock(priv->mc13xxx);
+
+	return ret;
+}
+
+static int mc13xxx_rtc_read_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	unsigned int seconds, days1, days2;
+
+	if (!priv->valid)
+		return -ENODATA;
+
+	do {
+		int ret;
+
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days1);
+		if (ret)
+			return ret;
+
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTOD, &seconds);
+		if (ret)
+			return ret;
+
+		ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days2);
+		if (ret)
+			return ret;
+	} while (days1 != days2);
+
+	rtc_time64_to_tm((time64_t)days1 * SEC_PER_DAY + seconds, tm);
+
+	return 0;
+}
+
+static int mc13xxx_rtc_set_time(struct device *dev, struct rtc_time *tm)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	unsigned int seconds, days;
+	unsigned int alarmseconds;
+	int ret;
+
+	days = div_s64_rem(rtc_tm_to_time64(tm), SEC_PER_DAY, &seconds);
+
+	mc13xxx_lock(priv->mc13xxx);
+
+	/*
+	 * temporarily invalidate alarm to prevent triggering it when the day is
+	 * already updated while the time isn't yet.
+	 */
+	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTODA, &alarmseconds);
+	if (unlikely(ret))
+		goto out;
+
+	if (alarmseconds < SEC_PER_DAY) {
+		ret = mc13xxx_reg_write(priv->mc13xxx,
+				MC13XXX_RTCTODA, 0x1ffff);
+		if (unlikely(ret))
+			goto out;
+	}
+
+	/*
+	 * write seconds=0 to prevent a day switch between writing days
+	 * and seconds below
+	 */
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCTOD, 0);
+	if (unlikely(ret))
+		goto out;
+
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCDAY, days);
+	if (unlikely(ret))
+		goto out;
+
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCTOD, seconds);
+	if (unlikely(ret))
+		goto out;
+
+	/* restore alarm */
+	if (alarmseconds < SEC_PER_DAY) {
+		ret = mc13xxx_reg_write(priv->mc13xxx,
+				MC13XXX_RTCTODA, alarmseconds);
+		if (unlikely(ret))
+			goto out;
+	}
+
+	if (!priv->valid) {
+		ret = mc13xxx_irq_unmask(priv->mc13xxx, MC13XXX_IRQ_RTCRST);
+	}
+
+out:
+	priv->valid = !ret;
+
+	mc13xxx_unlock(priv->mc13xxx);
+
+	return ret;
+}
+
+static int mc13xxx_rtc_read_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	unsigned int seconds, days;
+	time64_t s1970;
+	int enabled, pending;
+	int ret;
+
+	mc13xxx_lock(priv->mc13xxx);
+
+	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCTODA, &seconds);
+	if (unlikely(ret))
+		goto out;
+	if (seconds >= SEC_PER_DAY) {
+		ret = -ENODATA;
+		goto out;
+	}
+
+	ret = mc13xxx_reg_read(priv->mc13xxx, MC13XXX_RTCDAY, &days);
+	if (unlikely(ret))
+		goto out;
+
+	ret = mc13xxx_irq_status(priv->mc13xxx, MC13XXX_IRQ_TODA,
+			&enabled, &pending);
+
+out:
+	mc13xxx_unlock(priv->mc13xxx);
+
+	if (ret)
+		return ret;
+
+	alarm->enabled = enabled;
+	alarm->pending = pending;
+
+	s1970 = (time64_t)days * SEC_PER_DAY + seconds;
+
+	rtc_time64_to_tm(s1970, &alarm->time);
+	dev_dbg(dev, "%s: %lld\n", __func__, (long long)s1970);
+
+	return 0;
+}
+
+static int mc13xxx_rtc_set_alarm(struct device *dev, struct rtc_wkalrm *alarm)
+{
+	struct mc13xxx_rtc *priv = dev_get_drvdata(dev);
+	time64_t s1970;
+	u32 seconds, days;
+	int ret;
+
+	mc13xxx_lock(priv->mc13xxx);
+
+	/* disable alarm to prevent false triggering */
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCTODA, 0x1ffff);
+	if (unlikely(ret))
+		goto out;
+
+	s1970 = rtc_tm_to_time64(&alarm->time);
+
+	dev_dbg(dev, "%s: %s %lld\n", __func__, alarm->enabled ? "on" : "off",
+			(long long)s1970);
+
+	ret = mc13xxx_rtc_irq_enable_unlocked(dev, alarm->enabled,
+			MC13XXX_IRQ_TODA);
+	if (unlikely(ret))
+		goto out;
+
+	days = div_s64_rem(s1970, SEC_PER_DAY, &seconds);
+
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCDAYA, days);
+	if (unlikely(ret))
+		goto out;
+
+	ret = mc13xxx_reg_write(priv->mc13xxx, MC13XXX_RTCTODA, seconds);
+
+out:
+	mc13xxx_unlock(priv->mc13xxx);
+
+	return ret;
+}
+
+static irqreturn_t mc13xxx_rtc_alarm_handler(int irq, void *dev)
+{
+	struct mc13xxx_rtc *priv = dev;
+
+	rtc_update_irq(priv->rtc, 1, RTC_IRQF | RTC_AF);
+
+	return IRQ_HANDLED;
+}
+
+static const struct rtc_class_ops mc13xxx_rtc_ops = {
+	.read_time = mc13xxx_rtc_read_time,
+	.set_time = mc13xxx_rtc_set_time,
+	.read_alarm = mc13xxx_rtc_read_alarm,
+	.set_alarm = mc13xxx_rtc_set_alarm,
+	.alarm_irq_enable = mc13xxx_rtc_alarm_irq_enable,
+};
+
+static irqreturn_t mc13xxx_rtc_reset_handler(int irq, void *dev)
+{
+	struct mc13xxx_rtc *priv = dev;
+	struct mc13xxx *mc13xxx = priv->mc13xxx;
+
+	priv->valid = 0;
+
+	mc13xxx_irq_mask(mc13xxx, irq);
+
+	return IRQ_HANDLED;
+}
+
+static int __init mc13xxx_rtc_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct mc13xxx_rtc *priv;
+	struct mc13xxx *mc13xxx;
+
+	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	mc13xxx = dev_get_drvdata(pdev->dev.parent);
+	priv->mc13xxx = mc13xxx;
+	priv->valid = 1;
+
+	priv->rtc = devm_rtc_allocate_device(&pdev->dev);
+	if (IS_ERR(priv->rtc))
+		return PTR_ERR(priv->rtc);
+	platform_set_drvdata(pdev, priv);
+
+	priv->rtc->ops = &mc13xxx_rtc_ops;
+	/* 15bit days + hours, minutes, seconds */
+	priv->rtc->range_max = (timeu64_t)(1 << 15) * SEC_PER_DAY - 1;
+
+	mc13xxx_lock(mc13xxx);
+
+	ret = mc13xxx_irq_request(mc13xxx, MC13XXX_IRQ_RTCRST,
+			mc13xxx_rtc_reset_handler, DRIVER_NAME, priv);
+	if (ret)
+		goto err_irq_request;
+
+	ret = mc13xxx_irq_request_nounmask(mc13xxx, MC13XXX_IRQ_TODA,
+			mc13xxx_rtc_alarm_handler, DRIVER_NAME, priv);
+	if (ret)
+		goto err_irq_request;
+
+	mc13xxx_unlock(mc13xxx);
+
+	ret = devm_rtc_register_device(priv->rtc);
+	if (ret) {
+		mc13xxx_lock(mc13xxx);
+		goto err_irq_request;
+	}
+
+	return 0;
+
+err_irq_request:
+	mc13xxx_irq_free(mc13xxx, MC13XXX_IRQ_TODA, priv);
+	mc13xxx_irq_free(mc13xxx, MC13XXX_IRQ_RTCRST, priv);
+
+	mc13xxx_unlock(mc13xxx);
+
+	return ret;
+}
+
+static void mc13xxx_rtc_remove(struct platform_device *pdev)
+{
+	struct mc13xxx_rtc *priv = platform_get_drvdata(pdev);
+
+	mc13xxx_lock(priv->mc13xxx);
+
+	mc13xxx_irq_free(priv->mc13xxx, MC13XXX_IRQ_TODA, priv);
+	mc13xxx_irq_free(priv->mc13xxx, MC13XXX_IRQ_RTCRST, priv);
+
+	mc13xxx_unlock(priv->mc13xxx);
+}
+
+static const struct platform_device_id mc13xxx_rtc_idtable[] = {
+	{
+		.name = "mc13783-rtc",
+	}, {
+		.name = "mc13892-rtc",
+	}, {
+		.name = "mc34708-rtc",
+	},
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(platform, mc13xxx_rtc_idtable);
+
+static struct platform_driver mc13xxx_rtc_driver = {
+	.id_table = mc13xxx_rtc_idtable,
+	.remove = mc13xxx_rtc_remove,
+	.driver = {
+		.name = DRIVER_NAME,
+	},
+};
+
+module_platform_driver_probe(mc13xxx_rtc_driver, &mc13xxx_rtc_probe);
+
+MODULE_AUTHOR("Sascha Hauer <s.hauer@pengutronix.de>");
+MODULE_DESCRIPTION("RTC driver for Freescale MC13XXX PMIC");
+MODULE_LICENSE("GPL v2");