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, 90 insertions, 0 deletions

diff --git a/drivers/hid/hid-belkin.c b/drivers/hid/hid-belkin.c
new file mode 100644
index 000000000..84695115d
--- /dev/null
+++ b/drivers/hid/hid-belkin.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for some belkin "special" devices
+ *
+ *  Copyright (c) 1999 Andreas Gal
+ *  Copyright (c) 2000-2005 Vojtech Pavlik <vojtech@suse.cz>
+ *  Copyright (c) 2005 Michael Haboustak <mike-@cinci.rr.com> for Concept2, Inc
+ *  Copyright (c) 2006-2007 Jiri Kosina
+ *  Copyright (c) 2008 Jiri Slaby
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define BELKIN_HIDDEV	0x01
+#define BELKIN_WKBD	0x02
+
+#define belkin_map_key_clear(c)	hid_map_usage_clear(hi, usage, bit, max, \
+					EV_KEY, (c))
+static int belkin_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+		struct hid_field *field, struct hid_usage *usage,
+		unsigned long **bit, int *max)
+{
+	const struct hid_device_id *id = hid_get_drvdata(hdev);
+	unsigned long quirks = id->driver_data;
+
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_CONSUMER ||
+			!(quirks & BELKIN_WKBD))
+		return 0;
+
+	switch (usage->hid & HID_USAGE) {
+	case 0x03a: belkin_map_key_clear(KEY_SOUND);		break;
+	case 0x03b: belkin_map_key_clear(KEY_CAMERA);		break;
+	case 0x03c: belkin_map_key_clear(KEY_DOCUMENTS);	break;
+	default:
+		return 0;
+	}
+	return 1;
+}
+
+static int belkin_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	unsigned long quirks = id->driver_data;
+	int ret;
+
+	hid_set_drvdata(hdev, (void *)id);
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		goto err_free;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT |
+		((quirks & BELKIN_HIDDEV) ? HID_CONNECT_HIDDEV_FORCE : 0));
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		goto err_free;
+	}
+
+	return 0;
+err_free:
+	return ret;
+}
+
+static const struct hid_device_id belkin_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_BELKIN, USB_DEVICE_ID_FLIP_KVM),
+		.driver_data = BELKIN_HIDDEV },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_LABTEC, USB_DEVICE_ID_LABTEC_WIRELESS_KEYBOARD),
+		.driver_data = BELKIN_WKBD },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, belkin_devices);
+
+static struct hid_driver belkin_driver = {
+	.name = "belkin",
+	.id_table = belkin_devices,
+	.input_mapping = belkin_input_mapping,
+	.probe = belkin_probe,
+};
+module_hid_driver(belkin_driver);
+
+MODULE_DESCRIPTION("HID driver for some belkin \"special\" devices");
+MODULE_LICENSE("GPL");