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, 127 insertions, 0 deletions

diff --git a/drivers/reset/reset-sky1-audss.c b/drivers/reset/reset-sky1-audss.c
new file mode 100644
index 000000000..d9735db68
--- /dev/null
+++ b/drivers/reset/reset-sky1-audss.c
@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Cix Sky1 Audio Subsystem reset controller driver
+ *
+ * Copyright 2026 Cix Technology Group Co., Ltd.
+ */
+
+#include <dt-bindings/reset/cix,sky1-audss-cru.h>
+
+#include <linux/auxiliary_bus.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+
+#define SKY1_RESET_SLEEP_US			50
+
+#define AUDSS_SW_RST			0x78
+
+struct sky1_audss_reset_map {
+	unsigned int offset;
+	unsigned int mask;
+};
+
+struct sky1_audss_reset {
+	struct reset_controller_dev rcdev;
+	struct regmap *regmap;
+	const struct sky1_audss_reset_map *map;
+};
+
+static const struct sky1_audss_reset_map sky1_audss_reset_map[] = {
+	[AUDSS_I2S0_SW_RST]   = { AUDSS_SW_RST, BIT(0) },
+	[AUDSS_I2S1_SW_RST]   = { AUDSS_SW_RST, BIT(1) },
+	[AUDSS_I2S2_SW_RST]   = { AUDSS_SW_RST, BIT(2) },
+	[AUDSS_I2S3_SW_RST]   = { AUDSS_SW_RST, BIT(3) },
+	[AUDSS_I2S4_SW_RST]   = { AUDSS_SW_RST, BIT(4) },
+	[AUDSS_I2S5_SW_RST]   = { AUDSS_SW_RST, BIT(5) },
+	[AUDSS_I2S6_SW_RST]   = { AUDSS_SW_RST, BIT(6) },
+	[AUDSS_I2S7_SW_RST]   = { AUDSS_SW_RST, BIT(7) },
+	[AUDSS_I2S8_SW_RST]   = { AUDSS_SW_RST, BIT(8) },
+	[AUDSS_I2S9_SW_RST]   = { AUDSS_SW_RST, BIT(9) },
+	[AUDSS_WDT_SW_RST]    = { AUDSS_SW_RST, BIT(10) },
+	[AUDSS_TIMER_SW_RST]  = { AUDSS_SW_RST, BIT(11) },
+	[AUDSS_MB0_SW_RST]    = { AUDSS_SW_RST, BIT(12) },
+	[AUDSS_MB1_SW_RST]    = { AUDSS_SW_RST, BIT(13) },
+	[AUDSS_HDA_SW_RST]    = { AUDSS_SW_RST, BIT(14) },
+	[AUDSS_DMAC_SW_RST]   = { AUDSS_SW_RST, BIT(15) },
+};
+
+static struct sky1_audss_reset *to_sky1_audss_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct sky1_audss_reset, rcdev);
+}
+
+static int sky1_audss_reset_set(struct reset_controller_dev *rcdev,
+				unsigned long id, bool assert)
+{
+	struct sky1_audss_reset *priv = to_sky1_audss_reset(rcdev);
+	const struct sky1_audss_reset_map *signal = &priv->map[id];
+	int ret;
+
+	ret = regmap_assign_bits(priv->regmap, signal->offset,
+				 signal->mask, !assert);
+	if (ret)
+		return ret;
+
+	fsleep(SKY1_RESET_SLEEP_US);
+	return 0;
+}
+
+static int sky1_audss_reset_assert(struct reset_controller_dev *rcdev,
+				   unsigned long id)
+{
+	return sky1_audss_reset_set(rcdev, id, true);
+}
+
+static int sky1_audss_reset_deassert(struct reset_controller_dev *rcdev,
+				     unsigned long id)
+{
+	return sky1_audss_reset_set(rcdev, id, false);
+}
+
+static const struct reset_control_ops sky1_audss_reset_ops = {
+	.assert   = sky1_audss_reset_assert,
+	.deassert = sky1_audss_reset_deassert,
+};
+
+static int sky1_audss_reset_probe(struct auxiliary_device *adev,
+				  const struct auxiliary_device_id *id)
+{
+	struct sky1_audss_reset *priv;
+	struct device *dev = &adev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	priv->regmap = dev_get_regmap(dev->parent, NULL);
+	if (!priv->regmap)
+		return dev_err_probe(dev, -ENODEV, "failed to get parent regmap\n");
+
+	priv->map = sky1_audss_reset_map;
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.nr_resets = ARRAY_SIZE(sky1_audss_reset_map);
+	priv->rcdev.ops = &sky1_audss_reset_ops;
+	priv->rcdev.of_node = dev->of_node;
+	priv->rcdev.dev = dev;
+
+	return devm_reset_controller_register(dev, &priv->rcdev);
+}
+
+static const struct auxiliary_device_id sky1_audss_reset_ids[] = {
+	{ .name = "clk_sky1_audss.reset" },
+	{ }
+};
+MODULE_DEVICE_TABLE(auxiliary, sky1_audss_reset_ids);
+
+static struct auxiliary_driver sky1_audss_reset_driver = {
+	.probe = sky1_audss_reset_probe,
+	.id_table = sky1_audss_reset_ids,
+};
+module_auxiliary_driver(sky1_audss_reset_driver);
+
+MODULE_AUTHOR("Joakim Zhang <joakim.zhang@cixtech.com>");
+MODULE_DESCRIPTION("Cix Sky1 Audio Subsystem reset driver");
+MODULE_LICENSE("GPL");