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, 91 insertions, 0 deletions

diff --git a/drivers/mfd/act8945a.c b/drivers/mfd/act8945a.c
new file mode 100644
index 000000000..cafefb445
--- /dev/null
+++ b/drivers/mfd/act8945a.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * MFD driver for Active-semi ACT8945a PMIC
+ *
+ * Copyright (C) 2015 Atmel Corporation.
+ *
+ * Author: Wenyou Yang <wenyou.yang@atmel.com>
+ */
+
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/regmap.h>
+
+static const struct mfd_cell act8945a_devs[] = {
+	{
+		.name = "act8945a-regulator",
+	},
+	{
+		.name = "act8945a-charger",
+		.of_compatible = "active-semi,act8945a-charger",
+	},
+};
+
+static const struct regmap_config act8945a_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int act8945a_i2c_probe(struct i2c_client *i2c)
+{
+	int ret;
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(i2c, &act8945a_regmap_config);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(&i2c->dev, "regmap init failed: %d\n", ret);
+		return ret;
+	}
+
+	i2c_set_clientdata(i2c, regmap);
+
+	ret = devm_mfd_add_devices(&i2c->dev, PLATFORM_DEVID_NONE,
+				   act8945a_devs, ARRAY_SIZE(act8945a_devs),
+				   NULL, 0, NULL);
+	if (ret) {
+		dev_err(&i2c->dev, "Failed to add sub devices\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct i2c_device_id act8945a_i2c_id[] = {
+	{ "act8945a" },
+	{}
+};
+MODULE_DEVICE_TABLE(i2c, act8945a_i2c_id);
+
+static const struct of_device_id act8945a_of_match[] = {
+	{ .compatible = "active-semi,act8945a", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, act8945a_of_match);
+
+static struct i2c_driver act8945a_i2c_driver = {
+	.driver = {
+		   .name = "act8945a",
+		   .of_match_table = act8945a_of_match,
+	},
+	.probe = act8945a_i2c_probe,
+	.id_table = act8945a_i2c_id,
+};
+
+static int __init act8945a_i2c_init(void)
+{
+	return i2c_add_driver(&act8945a_i2c_driver);
+}
+subsys_initcall(act8945a_i2c_init);
+
+static void __exit act8945a_i2c_exit(void)
+{
+	i2c_del_driver(&act8945a_i2c_driver);
+}
+module_exit(act8945a_i2c_exit);
+
+MODULE_DESCRIPTION("ACT8945A PMIC multi-function driver");
+MODULE_AUTHOR("Wenyou Yang <wenyou.yang@atmel.com>");
+MODULE_LICENSE("GPL");