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, 79 insertions, 0 deletions

diff --git a/drivers/hid/hid-ezkey.c b/drivers/hid/hid-ezkey.c
new file mode 100644
index 000000000..0e28bc0b8
--- /dev/null
+++ b/drivers/hid/hid-ezkey.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for some ezkey "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/input.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define ez_map_rel(c)	hid_map_usage(hi, usage, bit, max, EV_REL, (c))
+#define ez_map_key(c)	hid_map_usage(hi, usage, bit, max, EV_KEY, (c))
+
+static int ez_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+		struct hid_field *field, struct hid_usage *usage,
+		unsigned long **bit, int *max)
+{
+	if ((usage->hid & HID_USAGE_PAGE) != HID_UP_CONSUMER)
+		return 0;
+
+	switch (usage->hid & HID_USAGE) {
+	case 0x230: ez_map_key(BTN_MOUSE);	break;
+	case 0x231: ez_map_rel(REL_WHEEL);	break;
+	/*
+	 * this keyboard has a scrollwheel implemented in
+	 * totally broken way. We map this usage temporarily
+	 * to HWHEEL and handle it in the event quirk handler
+	 */
+	case 0x232: ez_map_rel(REL_HWHEEL);	break;
+	default:
+		return 0;
+	}
+	return 1;
+}
+
+static int ez_event(struct hid_device *hdev, struct hid_field *field,
+		struct hid_usage *usage, __s32 value)
+{
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !field->hidinput ||
+			!usage->type)
+		return 0;
+
+	/* handle the temporary quirky mapping to HWHEEL */
+	if (usage->type == EV_REL && usage->code == REL_HWHEEL) {
+		struct input_dev *input = field->hidinput->input;
+		input_event(input, usage->type, REL_WHEEL, -value);
+		return 1;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id ez_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_EZKEY, USB_DEVICE_ID_BTC_8193) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, ez_devices);
+
+static struct hid_driver ez_driver = {
+	.name = "ezkey",
+	.id_table = ez_devices,
+	.input_mapping = ez_input_mapping,
+	.event = ez_event,
+};
+module_hid_driver(ez_driver);
+
+MODULE_DESCRIPTION("HID driver for some ezkey \"special\" devices");
+MODULE_LICENSE("GPL");