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/acpi/event.c b/drivers/acpi/event.c
new file mode 100644
index 000000000..4d840d2e7
--- /dev/null
+++ b/drivers/acpi/event.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * event.c - exporting ACPI events via procfs
+ *
+ *  Copyright (C) 2001, 2002 Andy Grover <andrew.grover@intel.com>
+ *  Copyright (C) 2001, 2002 Paul Diefenbaugh <paul.s.diefenbaugh@intel.com>
+ *
+ */
+
+#define pr_fmt(fmt) "ACPI: " fmt
+
+#include <linux/spinlock.h>
+#include <linux/export.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/gfp.h>
+#include <linux/acpi.h>
+#include <net/netlink.h>
+#include <net/genetlink.h>
+
+#include "internal.h"
+
+/* ACPI notifier chain */
+static BLOCKING_NOTIFIER_HEAD(acpi_chain_head);
+
+int acpi_notifier_call_chain(const char *device_class,
+			     const char *bus_id, u32 type, u32 data)
+{
+	struct acpi_bus_event event;
+
+	strscpy(event.device_class, device_class);
+	strscpy(event.bus_id, bus_id);
+	event.type = type;
+	event.data = data;
+	return (blocking_notifier_call_chain(&acpi_chain_head, 0, (void *)&event)
+			== NOTIFY_BAD) ? -EINVAL : 0;
+}
+EXPORT_SYMBOL(acpi_notifier_call_chain);
+
+int register_acpi_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&acpi_chain_head, nb);
+}
+EXPORT_SYMBOL(register_acpi_notifier);
+
+int unregister_acpi_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&acpi_chain_head, nb);
+}
+EXPORT_SYMBOL(unregister_acpi_notifier);
+
+#ifdef CONFIG_NET
+static unsigned int acpi_event_seqnum;
+struct acpi_genl_event {
+	acpi_device_class device_class;
+	char bus_id[15];
+	u32 type;
+	u32 data;
+};
+
+/* attributes of acpi_genl_family */
+enum {
+	ACPI_GENL_ATTR_UNSPEC,
+	ACPI_GENL_ATTR_EVENT,	/* ACPI event info needed by user space */
+	__ACPI_GENL_ATTR_MAX,
+};
+#define ACPI_GENL_ATTR_MAX (__ACPI_GENL_ATTR_MAX - 1)
+
+/* commands supported by the acpi_genl_family */
+enum {
+	ACPI_GENL_CMD_UNSPEC,
+	ACPI_GENL_CMD_EVENT,	/* kernel->user notifications for ACPI events */
+	__ACPI_GENL_CMD_MAX,
+};
+#define ACPI_GENL_CMD_MAX (__ACPI_GENL_CMD_MAX - 1)
+
+#define ACPI_GENL_FAMILY_NAME		"acpi_event"
+#define ACPI_GENL_VERSION		0x01
+#define ACPI_GENL_MCAST_GROUP_NAME 	"acpi_mc_group"
+
+static const struct genl_multicast_group acpi_event_mcgrps[] = {
+	{ .name = ACPI_GENL_MCAST_GROUP_NAME, },
+};
+
+static struct genl_family acpi_event_genl_family __ro_after_init = {
+	.module = THIS_MODULE,
+	.name = ACPI_GENL_FAMILY_NAME,
+	.version = ACPI_GENL_VERSION,
+	.maxattr = ACPI_GENL_ATTR_MAX,
+	.mcgrps = acpi_event_mcgrps,
+	.n_mcgrps = ARRAY_SIZE(acpi_event_mcgrps),
+};
+
+int acpi_bus_generate_netlink_event(const char *device_class,
+				      const char *bus_id,
+				      u8 type, int data)
+{
+	struct sk_buff *skb;
+	struct nlattr *attr;
+	struct acpi_genl_event *event;
+	void *msg_header;
+	int size;
+
+	/* allocate memory */
+	size = nla_total_size(sizeof(struct acpi_genl_event)) +
+	    nla_total_size(0);
+
+	skb = genlmsg_new(size, GFP_ATOMIC);
+	if (!skb)
+		return -ENOMEM;
+
+	/* add the genetlink message header */
+	msg_header = genlmsg_put(skb, 0, acpi_event_seqnum++,
+				 &acpi_event_genl_family, 0,
+				 ACPI_GENL_CMD_EVENT);
+	if (!msg_header) {
+		nlmsg_free(skb);
+		return -ENOMEM;
+	}
+
+	/* fill the data */
+	attr =
+	    nla_reserve(skb, ACPI_GENL_ATTR_EVENT,
+			sizeof(struct acpi_genl_event));
+	if (!attr) {
+		nlmsg_free(skb);
+		return -EINVAL;
+	}
+
+	event = nla_data(attr);
+	memset(event, 0, sizeof(struct acpi_genl_event));
+
+	strscpy(event->device_class, device_class, sizeof(event->device_class));
+	strscpy(event->bus_id, bus_id, sizeof(event->bus_id));
+	event->type = type;
+	event->data = data;
+
+	/* send multicast genetlink message */
+	genlmsg_end(skb, msg_header);
+
+	genlmsg_multicast(&acpi_event_genl_family, skb, 0, 0, GFP_ATOMIC);
+	return 0;
+}
+
+EXPORT_SYMBOL(acpi_bus_generate_netlink_event);
+
+static int __init acpi_event_genetlink_init(void)
+{
+	return genl_register_family(&acpi_event_genl_family);
+}
+
+#else
+int acpi_bus_generate_netlink_event(const char *device_class,
+				      const char *bus_id,
+				      u8 type, int data)
+{
+	return 0;
+}
+
+EXPORT_SYMBOL(acpi_bus_generate_netlink_event);
+
+static int acpi_event_genetlink_init(void)
+{
+	return -ENODEV;
+}
+#endif
+
+static int __init acpi_event_init(void)
+{
+	int error;
+
+	if (acpi_disabled)
+		return 0;
+
+	/* create genetlink for acpi event */
+	error = acpi_event_genetlink_init();
+	if (error)
+		pr_warn("Failed to create genetlink family for ACPI event\n");
+
+	return 0;
+}
+
+fs_initcall(acpi_event_init);