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-speedlink.c b/drivers/hid/hid-speedlink.c
new file mode 100644
index 000000000..22ee078c4
--- /dev/null
+++ b/drivers/hid/hid-speedlink.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Speedlink Vicious and Divine Cezanne (USB mouse).
+ *  Fixes "jumpy" cursor and removes nonexistent keyboard LEDS from
+ *  the HID descriptor.
+ *
+ *  Copyright (c) 2011, 2013 Stefan Kriwanek <dev@stefankriwanek.de>
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static const struct hid_device_id speedlink_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_X_TENSIONS, USB_DEVICE_ID_SPEEDLINK_VAD_CEZANNE)},
+	{ }
+};
+
+static int speedlink_input_mapping(struct hid_device *hdev,
+		struct hid_input *hi,
+		struct hid_field *field, struct hid_usage *usage,
+		unsigned long **bit, int *max)
+{
+	/*
+	 * The Cezanne mouse has a second "keyboard" USB endpoint for it is
+	 * able to map keyboard events to the button presses.
+	 * It sends a standard keyboard report descriptor, though, whose
+	 * LEDs we ignore.
+	 */
+	switch (usage->hid & HID_USAGE_PAGE) {
+	case HID_UP_LED:
+		return -1;
+	}
+	return 0;
+}
+
+static int speedlink_event(struct hid_device *hdev, struct hid_field *field,
+		struct hid_usage *usage, __s32 value)
+{
+	/* No other conditions due to usage_table. */
+
+	/* This fixes the "jumpy" cursor occuring due to invalid events sent
+	 * by the device. Some devices only send them with value==+256, others
+	 * don't. However, catching abs(value)>=256 is restrictive enough not
+	 * to interfere with devices that were bug-free (has been tested).
+	 */
+	if (abs(value) >= 256)
+		return 1;
+	/* Drop useless distance 0 events (on button clicks etc.) as well */
+	if (value == 0)
+		return 1;
+
+	return 0;
+}
+
+MODULE_DEVICE_TABLE(hid, speedlink_devices);
+
+static const struct hid_usage_id speedlink_grabbed_usages[] = {
+	{ HID_GD_X, EV_REL, 0 },
+	{ HID_GD_Y, EV_REL, 1 },
+	{ HID_ANY_ID - 1, HID_ANY_ID - 1, HID_ANY_ID - 1}
+};
+
+static struct hid_driver speedlink_driver = {
+	.name = "speedlink",
+	.id_table = speedlink_devices,
+	.usage_table = speedlink_grabbed_usages,
+	.input_mapping = speedlink_input_mapping,
+	.event = speedlink_event,
+};
+module_hid_driver(speedlink_driver);
+
+MODULE_DESCRIPTION("HID driver for Speedlink Vicious and Divine Cezanne (USB mouse)");
+MODULE_LICENSE("GPL");