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, 167 insertions, 0 deletions

diff --git a/drivers/hid/hid-a4tech.c b/drivers/hid/hid-a4tech.c
new file mode 100644
index 000000000..54bfaf611
--- /dev/null
+++ b/drivers/hid/hid-a4tech.c
@@ -0,0 +1,167 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for some a4tech "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 <linux/slab.h>
+
+#include "hid-ids.h"
+
+#define A4_2WHEEL_MOUSE_HACK_7	0x01
+#define A4_2WHEEL_MOUSE_HACK_B8	0x02
+
+#define A4_WHEEL_ORIENTATION	(HID_UP_GENDESK | 0x000000b8)
+
+struct a4tech_sc {
+	unsigned long quirks;
+	unsigned int hw_wheel;
+	__s32 delayed_value;
+};
+
+static int a4_input_mapping(struct hid_device *hdev, struct hid_input *hi,
+			    struct hid_field *field, struct hid_usage *usage,
+			    unsigned long **bit, int *max)
+{
+	struct a4tech_sc *a4 = hid_get_drvdata(hdev);
+
+	if (a4->quirks & A4_2WHEEL_MOUSE_HACK_B8 &&
+	    usage->hid == A4_WHEEL_ORIENTATION) {
+		/*
+		 * We do not want to have this usage mapped to anything as it's
+		 * nonstandard and doesn't really behave like an HID report.
+		 * It's only selecting the orientation (vertical/horizontal) of
+		 * the previous mouse wheel report. The input_events will be
+		 * generated once both reports are recorded in a4_event().
+		 */
+		return -1;
+	}
+
+	return 0;
+
+}
+
+static int a4_input_mapped(struct hid_device *hdev, struct hid_input *hi,
+		struct hid_field *field, struct hid_usage *usage,
+		unsigned long **bit, int *max)
+{
+	struct a4tech_sc *a4 = hid_get_drvdata(hdev);
+
+	if (usage->type == EV_REL && usage->code == REL_WHEEL_HI_RES) {
+		set_bit(REL_HWHEEL, *bit);
+		set_bit(REL_HWHEEL_HI_RES, *bit);
+	}
+
+	if ((a4->quirks & A4_2WHEEL_MOUSE_HACK_7) && usage->hid == 0x00090007)
+		return -1;
+
+	return 0;
+}
+
+static int a4_event(struct hid_device *hdev, struct hid_field *field,
+		struct hid_usage *usage, __s32 value)
+{
+	struct a4tech_sc *a4 = hid_get_drvdata(hdev);
+	struct input_dev *input;
+
+	if (!(hdev->claimed & HID_CLAIMED_INPUT) || !field->hidinput)
+		return 0;
+
+	input = field->hidinput->input;
+
+	if (a4->quirks & A4_2WHEEL_MOUSE_HACK_B8) {
+		if (usage->type == EV_REL && usage->code == REL_WHEEL_HI_RES) {
+			a4->delayed_value = value;
+			return 1;
+		}
+
+		if (usage->hid == A4_WHEEL_ORIENTATION) {
+			input_event(input, EV_REL, value ? REL_HWHEEL :
+					REL_WHEEL, a4->delayed_value);
+			input_event(input, EV_REL, value ? REL_HWHEEL_HI_RES :
+					REL_WHEEL_HI_RES, a4->delayed_value * 120);
+			return 1;
+		}
+	}
+
+	if ((a4->quirks & A4_2WHEEL_MOUSE_HACK_7) && usage->hid == 0x00090007) {
+		a4->hw_wheel = !!value;
+		return 1;
+	}
+
+	if (usage->code == REL_WHEEL_HI_RES && a4->hw_wheel) {
+		input_event(input, usage->type, REL_HWHEEL, value);
+		input_event(input, usage->type, REL_HWHEEL_HI_RES, value * 120);
+		return 1;
+	}
+
+	return 0;
+}
+
+static int a4_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	struct a4tech_sc *a4;
+	int ret;
+
+	a4 = devm_kzalloc(&hdev->dev, sizeof(*a4), GFP_KERNEL);
+	if (a4 == NULL) {
+		hid_err(hdev, "can't alloc device descriptor\n");
+		return -ENOMEM;
+	}
+
+	a4->quirks = id->driver_data;
+
+	hid_set_drvdata(hdev, a4);
+
+	ret = hid_parse(hdev);
+	if (ret) {
+		hid_err(hdev, "parse failed\n");
+		return ret;
+	}
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (ret) {
+		hid_err(hdev, "hw start failed\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id a4_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_A4TECH, USB_DEVICE_ID_A4TECH_WCP32PU),
+		.driver_data = A4_2WHEEL_MOUSE_HACK_7 },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_A4TECH, USB_DEVICE_ID_A4TECH_X5_005D),
+		.driver_data = A4_2WHEEL_MOUSE_HACK_B8 },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_A4TECH, USB_DEVICE_ID_A4TECH_RP_649),
+		.driver_data = A4_2WHEEL_MOUSE_HACK_B8 },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_A4TECH, USB_DEVICE_ID_A4TECH_NB_95),
+		.driver_data = A4_2WHEEL_MOUSE_HACK_B8 },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, a4_devices);
+
+static struct hid_driver a4_driver = {
+	.name = "a4tech",
+	.id_table = a4_devices,
+	.input_mapping = a4_input_mapping,
+	.input_mapped = a4_input_mapped,
+	.event = a4_event,
+	.probe = a4_probe,
+};
+module_hid_driver(a4_driver);
+
+MODULE_DESCRIPTION("HID driver for some a4tech \"special\" devices");
+MODULE_LICENSE("GPL");