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, 205 insertions, 0 deletions

diff --git a/drivers/clk/qcom/clk-ref.c b/drivers/clk/qcom/clk-ref.c
new file mode 100644
index 000000000..3efdf6749
--- /dev/null
+++ b/drivers/clk/qcom/clk-ref.c
@@ -0,0 +1,205 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2026, Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clk/qcom.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define QCOM_CLK_REF_EN_MASK BIT(0)
+
+struct qcom_clk_ref_provider {
+	size_t num_refs;
+	struct qcom_clk_ref refs[] __counted_by(num_refs);
+};
+
+static inline struct qcom_clk_ref *to_qcom_clk_ref(struct clk_hw *hw)
+{
+	return container_of(hw, struct qcom_clk_ref, hw);
+}
+
+static const struct clk_parent_data qcom_clk_ref_parent_data = {
+	.index = 0,
+};
+
+static int qcom_clk_ref_prepare(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	int ret;
+
+	if (!rclk->desc.num_regulators)
+		return 0;
+
+	ret = regulator_bulk_enable(rclk->desc.num_regulators, rclk->regulators);
+	if (ret)
+		pr_err("Failed to enable regulators for %s: %d\n",
+		       clk_hw_get_name(hw), ret);
+
+	return ret;
+}
+
+static void qcom_clk_ref_unprepare(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+
+	if (rclk->desc.num_regulators)
+		regulator_bulk_disable(rclk->desc.num_regulators, rclk->regulators);
+}
+
+static int qcom_clk_ref_enable(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	int ret;
+
+	ret = regmap_set_bits(rclk->regmap, rclk->desc.offset, QCOM_CLK_REF_EN_MASK);
+	if (ret)
+		return ret;
+
+	udelay(10);
+
+	return 0;
+}
+
+static void qcom_clk_ref_disable(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+
+	regmap_clear_bits(rclk->regmap, rclk->desc.offset, QCOM_CLK_REF_EN_MASK);
+	udelay(10);
+}
+
+static int qcom_clk_ref_is_enabled(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	u32 val;
+	int ret;
+
+	ret = regmap_read(rclk->regmap, rclk->desc.offset, &val);
+	if (ret)
+		return 0;
+
+	return !!(val & QCOM_CLK_REF_EN_MASK);
+}
+
+static const struct clk_ops qcom_clk_ref_ops = {
+	.prepare = qcom_clk_ref_prepare,
+	.unprepare = qcom_clk_ref_unprepare,
+	.enable = qcom_clk_ref_enable,
+	.disable = qcom_clk_ref_disable,
+	.is_enabled = qcom_clk_ref_is_enabled,
+};
+
+static int qcom_clk_ref_register(struct device *dev, struct regmap *regmap,
+				 struct qcom_clk_ref *clk_refs,
+				 const struct qcom_clk_ref_desc * const *descs,
+				 size_t num_clk_refs)
+{
+	const struct qcom_clk_ref_desc *desc;
+	struct clk_init_data init_data = {};
+	struct qcom_clk_ref *clk_ref;
+	size_t clk_idx;
+	unsigned int i;
+	int ret;
+
+	for (clk_idx = 0; clk_idx < num_clk_refs; clk_idx++) {
+		clk_ref = &clk_refs[clk_idx];
+		desc = descs[clk_idx];
+
+		/* Skip unpopulated indices; the array is indexed by clock ID. */
+		if (!desc)
+			continue;
+
+		if (WARN_ON(!desc->name))
+			continue;
+
+		clk_ref->regmap = regmap;
+		clk_ref->desc = *desc;
+
+		if (clk_ref->desc.num_regulators) {
+			clk_ref->regulators = devm_kcalloc(dev, clk_ref->desc.num_regulators,
+							   sizeof(*clk_ref->regulators),
+							   GFP_KERNEL);
+			if (!clk_ref->regulators)
+				return -ENOMEM;
+
+			for (i = 0; i < clk_ref->desc.num_regulators; i++)
+				clk_ref->regulators[i].supply =
+					clk_ref->desc.regulator_names[i];
+
+			ret = devm_regulator_bulk_get(dev, clk_ref->desc.num_regulators,
+						      clk_ref->regulators);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "Failed to get regulators for %s\n",
+						     clk_ref->desc.name);
+		}
+
+		init_data.name = clk_ref->desc.name;
+		init_data.parent_data = &qcom_clk_ref_parent_data;
+		init_data.num_parents = 1;
+		init_data.ops = &qcom_clk_ref_ops;
+		clk_ref->hw.init = &init_data;
+
+		ret = devm_clk_hw_register(dev, &clk_ref->hw);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static struct clk_hw *qcom_clk_ref_provider_get(struct of_phandle_args *clkspec, void *data)
+{
+	struct qcom_clk_ref_provider *provider = data;
+	unsigned int idx = clkspec->args[0];
+
+	if (idx >= provider->num_refs)
+		return ERR_PTR(-EINVAL);
+
+	if (!provider->refs[idx].regmap)
+		return ERR_PTR(-ENOENT);
+
+	return &provider->refs[idx].hw;
+}
+
+int qcom_clk_ref_probe(struct platform_device *pdev,
+		       const struct regmap_config *config,
+		       const struct qcom_clk_ref_desc * const *descs,
+		       size_t num_clk_refs)
+{
+	struct qcom_clk_ref_provider *provider;
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+	void __iomem *base;
+	int ret;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	regmap = devm_regmap_init_mmio(dev, base, config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	provider = devm_kzalloc(dev, struct_size(provider, refs, num_clk_refs),
+				GFP_KERNEL);
+	if (!provider)
+		return -ENOMEM;
+
+	provider->num_refs = num_clk_refs;
+
+	ret = qcom_clk_ref_register(dev, regmap, provider->refs, descs,
+				    provider->num_refs);
+	if (ret)
+		return ret;
+
+	return devm_of_clk_add_hw_provider(dev, qcom_clk_ref_provider_get, provider);
+}
+EXPORT_SYMBOL_GPL(qcom_clk_ref_probe);