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/input/touchscreen/touchwin.c b/drivers/input/touchscreen/touchwin.c
new file mode 100644
index 000000000..3ed33378d
--- /dev/null
+++ b/drivers/input/touchscreen/touchwin.c
@@ -0,0 +1,184 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Touchwindow serial touchscreen driver
+ *
+ * Copyright (c) 2006 Rick Koch <n1gp@hotmail.com>
+ *
+ * Based on MicroTouch driver (drivers/input/touchscreen/mtouch.c)
+ * Copyright (c) 2004 Vojtech Pavlik
+ * and Dan Streetman <ddstreet@ieee.org>
+ */
+
+
+/*
+ * 2005/02/19 Rick Koch:
+ *   The Touchwindow I used is made by Edmark Corp. and
+ *   constantly outputs a stream of 0's unless it is touched.
+ *   It then outputs 3 bytes: X, Y, and a copy of Y.
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"Touchwindow serial touchscreen driver"
+
+MODULE_AUTHOR("Rick Koch <n1gp@hotmail.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define TW_LENGTH 3
+
+#define TW_MIN_XC 0
+#define TW_MAX_XC 0xff
+#define TW_MIN_YC 0
+#define TW_MAX_YC 0xff
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct tw {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	int touched;
+	unsigned char data[TW_LENGTH];
+	char phys[32];
+};
+
+static irqreturn_t tw_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct tw *tw = serio_get_drvdata(serio);
+	struct input_dev *dev = tw->dev;
+
+	if (data) {		/* touch */
+		tw->touched = 1;
+		tw->data[tw->idx++] = data;
+		/* a full packet ends the accumulation, valid or not */
+		if (tw->idx == TW_LENGTH) {
+			/* report only if the two Y's are the same */
+			if (tw->data[1] == tw->data[2]) {
+				input_report_abs(dev, ABS_X, tw->data[0]);
+				input_report_abs(dev, ABS_Y, tw->data[1]);
+				input_report_key(dev, BTN_TOUCH, 1);
+				input_sync(dev);
+			}
+			tw->idx = 0;
+		}
+	} else if (tw->touched) {	/* untouch */
+		input_report_key(dev, BTN_TOUCH, 0);
+		input_sync(dev);
+		tw->idx = 0;
+		tw->touched = 0;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * tw_disconnect() is the opposite of tw_connect()
+ */
+
+static void tw_disconnect(struct serio *serio)
+{
+	struct tw *tw = serio_get_drvdata(serio);
+
+	input_get_device(tw->dev);
+	input_unregister_device(tw->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(tw->dev);
+	kfree(tw);
+}
+
+/*
+ * tw_connect() is the routine that is called when someone adds a
+ * new serio device that supports the Touchwin protocol and registers it as
+ * an input device.
+ */
+
+static int tw_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct tw *tw;
+	struct input_dev *input_dev;
+	int err;
+
+	tw = kzalloc_obj(*tw);
+	input_dev = input_allocate_device();
+	if (!tw || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	tw->serio = serio;
+	tw->dev = input_dev;
+	scnprintf(tw->phys, sizeof(tw->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "Touchwindow Serial TouchScreen";
+	input_dev->phys = tw->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_TOUCHWIN;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+	input_set_abs_params(tw->dev, ABS_X, TW_MIN_XC, TW_MAX_XC, 0, 0);
+	input_set_abs_params(tw->dev, ABS_Y, TW_MIN_YC, TW_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, tw);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(tw->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(tw);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id tw_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_TOUCHWIN,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, tw_serio_ids);
+
+static struct serio_driver tw_drv = {
+	.driver		= {
+		.name	= "touchwin",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= tw_serio_ids,
+	.interrupt	= tw_interrupt,
+	.connect	= tw_connect,
+	.disconnect	= tw_disconnect,
+};
+
+module_serio_driver(tw_drv);