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, 159 insertions, 0 deletions

diff --git a/drivers/mfd/88pm80x.c b/drivers/mfd/88pm80x.c
new file mode 100644
index 000000000..bbc1a87f0
--- /dev/null
+++ b/drivers/mfd/88pm80x.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * I2C driver for Marvell 88PM80x
+ *
+ * Copyright (C) 2012 Marvell International Ltd.
+ * Haojian Zhuang <haojian.zhuang@marvell.com>
+ * Joseph(Yossi) Hanin <yhanin@marvell.com>
+ * Qiao Zhou <zhouqiao@marvell.com>
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/mfd/88pm80x.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/err.h>
+
+/* 88pm80x chips have same definition for chip id register. */
+#define PM80X_CHIP_ID			(0x00)
+#define PM80X_CHIP_ID_NUM(x)		(((x) >> 5) & 0x7)
+#define PM80X_CHIP_ID_REVISION(x)	((x) & 0x1F)
+
+struct pm80x_chip_mapping {
+	unsigned int	id;
+	int		type;
+};
+
+static struct pm80x_chip_mapping chip_mapping[] = {
+	/* 88PM800 chip id number */
+	{0x3,	CHIP_PM800},
+	/* 88PM805 chip id number */
+	{0x0,	CHIP_PM805},
+	/* 88PM860 chip id number */
+	{0x4,	CHIP_PM860},
+};
+
+/*
+ * workaround: some registers needed by pm805 are defined in pm800, so
+ * need to use this global variable to maintain the relation between
+ * pm800 and pm805. would remove it after HW chip fixes the issue.
+ */
+static struct pm80x_chip *g_pm80x_chip;
+
+const struct regmap_config pm80x_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+EXPORT_SYMBOL_GPL(pm80x_regmap_config);
+
+
+int pm80x_init(struct i2c_client *client)
+{
+	struct pm80x_chip *chip;
+	struct regmap *map;
+	unsigned int val;
+	int i, ret = 0;
+
+	chip =
+	    devm_kzalloc(&client->dev, sizeof(struct pm80x_chip), GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+
+	map = devm_regmap_init_i2c(client, &pm80x_regmap_config);
+	if (IS_ERR(map)) {
+		ret = PTR_ERR(map);
+		dev_err(&client->dev, "Failed to allocate register map: %d\n",
+			ret);
+		return ret;
+	}
+
+	chip->client = client;
+	chip->regmap = map;
+
+	chip->irq = client->irq;
+
+	chip->dev = &client->dev;
+	i2c_set_clientdata(chip->client, chip);
+
+	ret = regmap_read(chip->regmap, PM80X_CHIP_ID, &val);
+	if (ret < 0) {
+		dev_err(chip->dev, "Failed to read CHIP ID: %d\n", ret);
+		return ret;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(chip_mapping); i++) {
+		if (chip_mapping[i].id == PM80X_CHIP_ID_NUM(val)) {
+			chip->type = chip_mapping[i].type;
+			break;
+		}
+	}
+
+	if (i == ARRAY_SIZE(chip_mapping)) {
+		dev_err(chip->dev,
+			"Failed to detect Marvell 88PM800:ChipID[0x%x]\n", val);
+		return -EINVAL;
+	}
+
+	device_init_wakeup(&client->dev, 1);
+
+	/*
+	 * workaround: set g_pm80x_chip to the first probed chip. if the
+	 * second chip is probed, just point to the companion to each
+	 * other so that pm805 can access those specific register. would
+	 * remove it after HW chip fixes the issue.
+	 */
+	if (!g_pm80x_chip)
+		g_pm80x_chip = chip;
+	else {
+		chip->companion = g_pm80x_chip->client;
+		g_pm80x_chip->companion = chip->client;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pm80x_init);
+
+int pm80x_deinit(void)
+{
+	/*
+	 * workaround: clear the dependency between pm800 and pm805.
+	 * would remove it after HW chip fixes the issue.
+	 */
+	if (g_pm80x_chip->companion)
+		g_pm80x_chip->companion = NULL;
+	else
+		g_pm80x_chip = NULL;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pm80x_deinit);
+
+static int pm80x_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pm80x_chip *chip = i2c_get_clientdata(client);
+
+	if (chip && chip->wu_flag)
+		if (device_may_wakeup(chip->dev))
+			enable_irq_wake(chip->irq);
+
+	return 0;
+}
+
+static int pm80x_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct pm80x_chip *chip = i2c_get_clientdata(client);
+
+	if (chip && chip->wu_flag)
+		if (device_may_wakeup(chip->dev))
+			disable_irq_wake(chip->irq);
+
+	return 0;
+}
+
+EXPORT_GPL_SIMPLE_DEV_PM_OPS(pm80x_pm_ops, pm80x_suspend, pm80x_resume);
+
+MODULE_DESCRIPTION("I2C Driver for Marvell 88PM80x");
+MODULE_AUTHOR("Qiao Zhou <zhouqiao@marvell.com>");
+MODULE_LICENSE("GPL");