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, 184 insertions, 0 deletions

diff --git a/drivers/pinctrl/pinctrl-generic-mux.c b/drivers/pinctrl/pinctrl-generic-mux.c
new file mode 100644
index 000000000..202b72351
--- /dev/null
+++ b/drivers/pinctrl/pinctrl-generic-mux.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic Pin Control Driver for Board-Level Mux Chips
+ * Copyright 2026 NXP
+ */
+
+#include <linux/cleanup.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/mutex.h>
+#include <linux/mux/consumer.h>
+#include <linux/platform_device.h>
+#include <linux/pinctrl/pinconf-generic.h>
+#include <linux/pinctrl/pinctrl.h>
+#include <linux/pinctrl/pinmux.h>
+#include <linux/slab.h>
+
+#include "core.h"
+#include "pinconf.h"
+#include "pinmux.h"
+#include "pinctrl-utils.h"
+
+struct mux_pin_function {
+	struct mux_state *mux_state;
+};
+
+struct mux_pinctrl {
+	struct device *dev;
+	struct pinctrl_dev *pctl;
+
+	/* mutex protect [pinctrl|pinmux]_generic functions */
+	struct mutex lock;
+};
+
+static int
+mux_pinmux_dt_node_to_map(struct pinctrl_dev *pctldev,
+			  struct device_node *np_config,
+			  struct pinctrl_map **maps, unsigned int *num_maps)
+{
+	unsigned int num_reserved_maps = 0;
+	struct mux_pin_function *function;
+	const char **group_names;
+	int ret;
+
+	function = devm_kzalloc(pctldev->dev, sizeof(*function), GFP_KERNEL);
+	if (!function)
+		return -ENOMEM;
+
+	group_names = devm_kcalloc(pctldev->dev, 1, sizeof(*group_names), GFP_KERNEL);
+	if (!group_names)
+		return -ENOMEM;
+
+	function->mux_state = devm_mux_state_get_from_np(pctldev->dev, NULL, np_config);
+	if (IS_ERR(function->mux_state))
+		return PTR_ERR(function->mux_state);
+
+	ret = pinctrl_generic_to_map(pctldev, np_config, np_config, maps,
+				     num_maps, &num_reserved_maps, group_names,
+				     0, &np_config->name, NULL, 0);
+
+	if (ret)
+		return ret;
+
+	ret = pinmux_generic_add_function(pctldev, np_config->name, group_names,
+					  1, function);
+	if (ret < 0) {
+		pinctrl_utils_free_map(pctldev, *maps, *num_maps);
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct pinctrl_ops mux_pinctrl_ops = {
+	.get_groups_count = pinctrl_generic_get_group_count,
+	.get_group_name = pinctrl_generic_get_group_name,
+	.get_group_pins = pinctrl_generic_get_group_pins,
+	.dt_node_to_map = mux_pinmux_dt_node_to_map,
+	.dt_free_map = pinctrl_utils_free_map,
+};
+
+static int mux_pinmux_set_mux(struct pinctrl_dev *pctldev,
+			      unsigned int func_selector,
+			      unsigned int group_selector)
+{
+	struct mux_pinctrl *mpctl = pinctrl_dev_get_drvdata(pctldev);
+	const struct function_desc *function;
+	struct mux_pin_function *func;
+	int ret;
+
+	guard(mutex)(&mpctl->lock);
+
+	function = pinmux_generic_get_function(pctldev, func_selector);
+	func = function->data;
+
+	ret = mux_state_try_select(func->mux_state);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void mux_pinmux_release_mux(struct pinctrl_dev *pctldev,
+				   unsigned int func_selector,
+				   unsigned int group_selector)
+{
+	struct mux_pinctrl *mpctl = pinctrl_dev_get_drvdata(pctldev);
+	const struct function_desc *function;
+	struct mux_pin_function *func;
+
+	guard(mutex)(&mpctl->lock);
+
+	function = pinmux_generic_get_function(pctldev, func_selector);
+	func = function->data;
+
+	mux_state_deselect(func->mux_state);
+}
+
+static const struct pinmux_ops mux_pinmux_ops = {
+	.get_functions_count = pinmux_generic_get_function_count,
+	.get_function_name = pinmux_generic_get_function_name,
+	.get_function_groups = pinmux_generic_get_function_groups,
+	.set_mux = mux_pinmux_set_mux,
+	.release_mux = mux_pinmux_release_mux,
+};
+
+static int mux_pinctrl_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct mux_pinctrl *mpctl;
+	struct pinctrl_desc *pctl_desc;
+	int ret;
+
+	mpctl = devm_kzalloc(dev, sizeof(*mpctl), GFP_KERNEL);
+	if (!mpctl)
+		return -ENOMEM;
+
+	mpctl->dev = dev;
+
+	platform_set_drvdata(pdev, mpctl);
+
+	pctl_desc = devm_kzalloc(dev, sizeof(*pctl_desc), GFP_KERNEL);
+	if (!pctl_desc)
+		return -ENOMEM;
+
+	ret = devm_mutex_init(dev, &mpctl->lock);
+	if (ret)
+		return ret;
+
+	pctl_desc->name = dev_name(dev);
+	pctl_desc->owner = THIS_MODULE;
+	pctl_desc->pctlops = &mux_pinctrl_ops;
+	pctl_desc->pmxops = &mux_pinmux_ops;
+
+	ret = devm_pinctrl_register_and_init(dev, pctl_desc, mpctl,
+					     &mpctl->pctl);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to register pinctrl.\n");
+
+	ret = pinctrl_enable(mpctl->pctl);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to enable pinctrl.\n");
+
+	return 0;
+}
+
+static const struct of_device_id mux_pinctrl_of_match[] = {
+	{ .compatible = "pinctrl-multiplexer" },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, mux_pinctrl_of_match);
+
+static struct platform_driver mux_pinctrl_driver = {
+	.driver = {
+		.name = "generic-pinctrl-mux",
+		.of_match_table = mux_pinctrl_of_match,
+	},
+	.probe = mux_pinctrl_probe,
+};
+module_platform_driver(mux_pinctrl_driver);
+
+MODULE_AUTHOR("Frank Li <Frank.Li@nxp.com>");
+MODULE_DESCRIPTION("Generic Pin Control Driver for Board-Level Mux Chips");
+MODULE_LICENSE("GPL");