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, 209 insertions, 0 deletions

diff --git a/drivers/phy/phy-common-props.c b/drivers/phy/phy-common-props.c
new file mode 100644
index 000000000..3e814bcbe
--- /dev/null
+++ b/drivers/phy/phy-common-props.c
@@ -0,0 +1,209 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * phy-common-props.c  --  Common PHY properties
+ *
+ * Copyright 2025-2026 NXP
+ */
+#include <linux/export.h>
+#include <linux/fwnode.h>
+#include <linux/phy/phy-common-props.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+
+/**
+ * fwnode_get_u32_prop_for_name - Find u32 property by name, or default value
+ * @fwnode: Pointer to firmware node, or NULL to use @default_val
+ * @name: Property name used as lookup key in @names_title (must not be NULL)
+ * @props_title: Name of u32 array property holding values
+ * @names_title: Name of string array property holding lookup keys
+ * @default_val: Default value if @fwnode is NULL or @props_title is empty
+ * @val: Pointer to store the returned value
+ *
+ * This function retrieves a u32 value from @props_title based on a name lookup
+ * in @names_title. The value stored in @val is determined as follows:
+ *
+ * - If @fwnode is NULL or @props_title is empty: @default_val is used
+ * - If @props_title has exactly one element and @names_title is empty:
+ *   that element is used
+ * - Otherwise: @val is set to the element at the same index where @name is
+ *   found in @names_title.
+ * - If @name is not found, the function looks for a "default" entry in
+ *   @names_title and uses the corresponding value from @props_title
+ *
+ * When both @props_title and @names_title are present, they must have the
+ * same number of elements (except when @props_title has exactly one element).
+ *
+ * Return: zero on success, negative error on failure.
+ */
+static int fwnode_get_u32_prop_for_name(struct fwnode_handle *fwnode,
+					const char *name,
+					const char *props_title,
+					const char *names_title,
+					unsigned int default_val,
+					unsigned int *val)
+{
+	int err, n_props, n_names, idx;
+	u32 *props;
+
+	if (!name) {
+		pr_err("Lookup key inside \"%s\" is mandatory\n", names_title);
+		return -EINVAL;
+	}
+
+	n_props = fwnode_property_count_u32(fwnode, props_title);
+	if (n_props <= 0) {
+		/* fwnode is NULL, or is missing requested property */
+		*val = default_val;
+		return 0;
+	}
+
+	n_names = fwnode_property_string_array_count(fwnode, names_title);
+	if (n_names >= 0 && n_props != n_names) {
+		pr_err("%pfw mismatch between \"%s\" and \"%s\" property count (%d vs %d)\n",
+		       fwnode, props_title, names_title, n_props, n_names);
+		return -EINVAL;
+	}
+
+	idx = fwnode_property_match_string(fwnode, names_title, name);
+	if (idx < 0)
+		idx = fwnode_property_match_string(fwnode, names_title, "default");
+	/*
+	 * If the mode name is missing, it can only mean the specified property
+	 * is the default one for all modes, so reject any other property count
+	 * than 1.
+	 */
+	if (idx < 0 && n_props != 1) {
+		pr_err("%pfw \"%s \" property has %d elements, but cannot find \"%s\" in \"%s\" and there is no default value\n",
+		       fwnode, props_title, n_props, name, names_title);
+		return -EINVAL;
+	}
+
+	if (n_props == 1) {
+		err = fwnode_property_read_u32(fwnode, props_title, val);
+		if (err)
+			return err;
+
+		return 0;
+	}
+
+	/* We implicitly know idx >= 0 here */
+	props = kcalloc(n_props, sizeof(*props), GFP_KERNEL);
+	if (!props)
+		return -ENOMEM;
+
+	err = fwnode_property_read_u32_array(fwnode, props_title, props, n_props);
+	if (err >= 0)
+		*val = props[idx];
+
+	kfree(props);
+
+	return err;
+}
+
+static int phy_get_polarity_for_mode(struct fwnode_handle *fwnode,
+				     const char *mode_name,
+				     unsigned int supported,
+				     unsigned int default_val,
+				     const char *polarity_prop,
+				     const char *names_prop,
+				     unsigned int *val)
+{
+	int err;
+
+	err = fwnode_get_u32_prop_for_name(fwnode, mode_name, polarity_prop,
+					   names_prop, default_val, val);
+	if (err)
+		return err;
+
+	if (!(supported & BIT(*val))) {
+		pr_err("%d is not a supported value for %pfw '%s' element '%s'\n",
+		       *val, fwnode, polarity_prop, mode_name);
+		err = -EOPNOTSUPP;
+	}
+
+	return err;
+}
+
+/**
+ * phy_get_rx_polarity - Get RX polarity for PHY differential lane
+ * @fwnode: Pointer to the PHY's firmware node.
+ * @mode_name: The name of the PHY mode to look up.
+ * @supported: Bit mask of PHY_POL_NORMAL, PHY_POL_INVERT and PHY_POL_AUTO
+ * @default_val: Default polarity value if property is missing
+ * @val: Pointer to returned polarity.
+ *
+ * Return: zero on success, negative error on failure.
+ */
+int __must_check phy_get_rx_polarity(struct fwnode_handle *fwnode,
+				     const char *mode_name,
+				     unsigned int supported,
+				     unsigned int default_val,
+				     unsigned int *val)
+{
+	return phy_get_polarity_for_mode(fwnode, mode_name, supported,
+					 default_val, "rx-polarity",
+					 "rx-polarity-names", val);
+}
+EXPORT_SYMBOL_GPL(phy_get_rx_polarity);
+
+/**
+ * phy_get_tx_polarity - Get TX polarity for PHY differential lane
+ * @fwnode: Pointer to the PHY's firmware node.
+ * @mode_name: The name of the PHY mode to look up.
+ * @supported: Bit mask of PHY_POL_NORMAL and PHY_POL_INVERT
+ * @default_val: Default polarity value if property is missing
+ * @val: Pointer to returned polarity.
+ *
+ * Return: zero on success, negative error on failure.
+ */
+int __must_check phy_get_tx_polarity(struct fwnode_handle *fwnode,
+				     const char *mode_name, unsigned int supported,
+				     unsigned int default_val, unsigned int *val)
+{
+	return phy_get_polarity_for_mode(fwnode, mode_name, supported,
+					 default_val, "tx-polarity",
+					 "tx-polarity-names", val);
+}
+EXPORT_SYMBOL_GPL(phy_get_tx_polarity);
+
+/**
+ * phy_get_manual_rx_polarity - Get manual RX polarity for PHY differential lane
+ * @fwnode: Pointer to the PHY's firmware node.
+ * @mode_name: The name of the PHY mode to look up.
+ * @val: Pointer to returned polarity.
+ *
+ * Helper for PHYs which do not support protocols with automatic RX polarity
+ * detection and correction.
+ *
+ * Return: zero on success, negative error on failure.
+ */
+int __must_check phy_get_manual_rx_polarity(struct fwnode_handle *fwnode,
+					    const char *mode_name,
+					    unsigned int *val)
+{
+	return phy_get_rx_polarity(fwnode, mode_name,
+				   BIT(PHY_POL_NORMAL) | BIT(PHY_POL_INVERT),
+				   PHY_POL_NORMAL, val);
+}
+EXPORT_SYMBOL_GPL(phy_get_manual_rx_polarity);
+
+/**
+ * phy_get_manual_tx_polarity - Get manual TX polarity for PHY differential lane
+ * @fwnode: Pointer to the PHY's firmware node.
+ * @mode_name: The name of the PHY mode to look up.
+ * @val: Pointer to returned polarity.
+ *
+ * Helper for PHYs without any custom default value for the TX polarity.
+ *
+ * Return: zero on success, negative error on failure.
+ */
+int __must_check phy_get_manual_tx_polarity(struct fwnode_handle *fwnode,
+					    const char *mode_name,
+					    unsigned int *val)
+{
+	return phy_get_tx_polarity(fwnode, mode_name,
+				   BIT(PHY_POL_NORMAL) | BIT(PHY_POL_INVERT),
+				   PHY_POL_NORMAL, val);
+}
+EXPORT_SYMBOL_GPL(phy_get_manual_tx_polarity);