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, 206 insertions, 0 deletions

diff --git a/drivers/reset/reset-sunplus.c b/drivers/reset/reset-sunplus.c
new file mode 100644
index 000000000..c136a1f07
--- /dev/null
+++ b/drivers/reset/reset-sunplus.c
@@ -0,0 +1,206 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/*
+ * SP7021 reset driver
+ *
+ * Copyright (C) Sunplus Technology Co., Ltd.
+ *       All rights reserved.
+ */
+
+#include <linux/io.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/reboot.h>
+
+/* HIWORD_MASK_REG BITS */
+#define BITS_PER_HWM_REG	16
+
+/* resets HW info: reg_index_shift */
+static const u32 sp_resets[] = {
+/* SP7021: mo_reset0 ~ mo_reset9 */
+	0x00,
+	0x02,
+	0x03,
+	0x04,
+	0x05,
+	0x06,
+	0x07,
+	0x08,
+	0x09,
+	0x0a,
+	0x0b,
+	0x0d,
+	0x0e,
+	0x0f,
+	0x10,
+	0x12,
+	0x14,
+	0x15,
+	0x16,
+	0x17,
+	0x18,
+	0x19,
+	0x1a,
+	0x1b,
+	0x1c,
+	0x1d,
+	0x1e,
+	0x1f,
+	0x20,
+	0x21,
+	0x22,
+	0x23,
+	0x24,
+	0x25,
+	0x26,
+	0x2a,
+	0x2b,
+	0x2d,
+	0x2e,
+	0x30,
+	0x31,
+	0x32,
+	0x33,
+	0x3d,
+	0x3e,
+	0x3f,
+	0x42,
+	0x44,
+	0x4b,
+	0x4c,
+	0x4d,
+	0x4e,
+	0x4f,
+	0x50,
+	0x55,
+	0x60,
+	0x61,
+	0x6a,
+	0x6f,
+	0x70,
+	0x73,
+	0x74,
+	0x86,
+	0x8a,
+	0x8b,
+	0x8d,
+	0x8e,
+	0x8f,
+	0x90,
+	0x92,
+	0x93,
+	0x94,
+	0x95,
+	0x96,
+	0x97,
+	0x98,
+	0x99,
+};
+
+struct sp_reset {
+	struct reset_controller_dev rcdev;
+	void __iomem *base;
+};
+
+static inline struct sp_reset *to_sp_reset(struct reset_controller_dev *rcdev)
+{
+	return container_of(rcdev, struct sp_reset, rcdev);
+}
+
+static int sp_reset_update(struct reset_controller_dev *rcdev,
+			   unsigned long id, bool assert)
+{
+	struct sp_reset *reset = to_sp_reset(rcdev);
+	int index = sp_resets[id] / BITS_PER_HWM_REG;
+	int shift = sp_resets[id] % BITS_PER_HWM_REG;
+	u32 val;
+
+	val = (1 << (16 + shift)) | (assert << shift);
+	writel(val, reset->base + (index * 4));
+
+	return 0;
+}
+
+static int sp_reset_assert(struct reset_controller_dev *rcdev,
+			   unsigned long id)
+{
+	return sp_reset_update(rcdev, id, true);
+}
+
+static int sp_reset_deassert(struct reset_controller_dev *rcdev,
+			     unsigned long id)
+{
+	return sp_reset_update(rcdev, id, false);
+}
+
+static int sp_reset_status(struct reset_controller_dev *rcdev,
+			   unsigned long id)
+{
+	struct sp_reset *reset = to_sp_reset(rcdev);
+	int index = sp_resets[id] / BITS_PER_HWM_REG;
+	int shift = sp_resets[id] % BITS_PER_HWM_REG;
+	u32 reg;
+
+	reg = readl(reset->base + (index * 4));
+
+	return !!(reg & BIT(shift));
+}
+
+static const struct reset_control_ops sp_reset_ops = {
+	.assert   = sp_reset_assert,
+	.deassert = sp_reset_deassert,
+	.status   = sp_reset_status,
+};
+
+static int sp_restart(struct sys_off_data *data)
+{
+	struct sp_reset *reset = data->cb_data;
+
+	sp_reset_assert(&reset->rcdev, 0);
+	sp_reset_deassert(&reset->rcdev, 0);
+
+	return NOTIFY_DONE;
+}
+
+static int sp_reset_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct sp_reset *reset;
+	struct resource *res;
+	int ret;
+
+	reset = devm_kzalloc(dev, sizeof(*reset), GFP_KERNEL);
+	if (!reset)
+		return -ENOMEM;
+
+	reset->base = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
+	if (IS_ERR(reset->base))
+		return PTR_ERR(reset->base);
+
+	reset->rcdev.ops = &sp_reset_ops;
+	reset->rcdev.owner = THIS_MODULE;
+	reset->rcdev.of_node = dev->of_node;
+	reset->rcdev.nr_resets = resource_size(res) / 4 * BITS_PER_HWM_REG;
+
+	ret = devm_reset_controller_register(dev, &reset->rcdev);
+	if (ret)
+		return ret;
+
+	return devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_RESTART,
+					     192, sp_restart, reset);
+}
+
+static const struct of_device_id sp_reset_dt_ids[] = {
+	{.compatible = "sunplus,sp7021-reset",},
+	{ /* sentinel */ },
+};
+
+static struct platform_driver sp_reset_driver = {
+	.probe = sp_reset_probe,
+	.driver = {
+		.name			= "sunplus-reset",
+		.of_match_table		= sp_reset_dt_ids,
+		.suppress_bind_attrs	= true,
+	},
+};
+builtin_platform_driver(sp_reset_driver);