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, 172 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/tsc40.c b/drivers/input/touchscreen/tsc40.c
new file mode 100644
index 000000000..2a28a309e
--- /dev/null
+++ b/drivers/input/touchscreen/tsc40.c
@@ -0,0 +1,172 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TSC-40 serial touchscreen driver. It should be compatible with
+ * TSC-10 and 25.
+ *
+ * Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define PACKET_LENGTH  5
+struct tsc_ser {
+	struct input_dev *dev;
+	struct serio *serio;
+	u32 idx;
+	unsigned char data[PACKET_LENGTH];
+	char phys[32];
+};
+
+static void tsc_process_data(struct tsc_ser *ptsc)
+{
+	struct input_dev *dev = ptsc->dev;
+	u8 *data = ptsc->data;
+	u32 x;
+	u32 y;
+
+	x = ((data[1] & 0x03) << 8) | data[2];
+	y = ((data[3] & 0x03) << 8) | data[4];
+
+	input_report_abs(dev, ABS_X, x);
+	input_report_abs(dev, ABS_Y, y);
+	input_report_key(dev, BTN_TOUCH, 1);
+
+	input_sync(dev);
+}
+
+static irqreturn_t tsc_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct tsc_ser *ptsc = serio_get_drvdata(serio);
+	struct input_dev *dev = ptsc->dev;
+
+	ptsc->data[ptsc->idx] = data;
+	switch (ptsc->idx++) {
+	case 0:
+		if (unlikely((data & 0x3e) != 0x10)) {
+			dev_dbg(&serio->dev,
+				"unsynchronized packet start (0x%02x)\n", data);
+			ptsc->idx = 0;
+		} else if (!(data & 0x01)) {
+			input_report_key(dev, BTN_TOUCH, 0);
+			input_sync(dev);
+			ptsc->idx = 0;
+		}
+		break;
+
+	case 1:
+	case 3:
+		if (unlikely(data & 0xfc)) {
+			dev_dbg(&serio->dev,
+				"unsynchronized data 0x%02x at offset %d\n",
+				data, ptsc->idx - 1);
+			ptsc->idx = 0;
+		}
+		break;
+
+	case 4:
+		tsc_process_data(ptsc);
+		ptsc->idx = 0;
+		break;
+	}
+
+	return IRQ_HANDLED;
+}
+
+static int tsc_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct tsc_ser *ptsc;
+	struct input_dev *input_dev;
+	int error;
+
+	ptsc = kzalloc_obj(*ptsc);
+	input_dev = input_allocate_device();
+	if (!ptsc || !input_dev) {
+		error = -ENOMEM;
+		goto fail1;
+	}
+
+	ptsc->serio = serio;
+	ptsc->dev = input_dev;
+	scnprintf(ptsc->phys, sizeof(ptsc->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "TSC-10/25/40 Serial TouchScreen";
+	input_dev->phys = ptsc->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_TSC40;
+	input_dev->id.product = 40;
+	input_dev->id.version = 0x0001;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	__set_bit(BTN_TOUCH, input_dev->keybit);
+	input_set_abs_params(ptsc->dev, ABS_X, 0, 0x3ff, 0, 0);
+	input_set_abs_params(ptsc->dev, ABS_Y, 0, 0x3ff, 0, 0);
+
+	serio_set_drvdata(serio, ptsc);
+
+	error = serio_open(serio, drv);
+	if (error)
+		goto fail2;
+
+	error = input_register_device(ptsc->dev);
+	if (error)
+		goto fail3;
+
+	return 0;
+
+fail3:
+	serio_close(serio);
+fail2:
+	serio_set_drvdata(serio, NULL);
+fail1:
+	input_free_device(input_dev);
+	kfree(ptsc);
+	return error;
+}
+
+static void tsc_disconnect(struct serio *serio)
+{
+	struct tsc_ser *ptsc = serio_get_drvdata(serio);
+
+	serio_close(serio);
+
+	input_unregister_device(ptsc->dev);
+	kfree(ptsc);
+
+	serio_set_drvdata(serio, NULL);
+}
+
+static const struct serio_device_id tsc_serio_ids[] = {
+	{
+		.type   = SERIO_RS232,
+		.proto  = SERIO_TSC40,
+		.id     = SERIO_ANY,
+		.extra  = SERIO_ANY,
+	},
+	{ 0 }
+};
+MODULE_DEVICE_TABLE(serio, tsc_serio_ids);
+
+#define DRIVER_DESC    "TSC-10/25/40 serial touchscreen driver"
+
+static struct serio_driver tsc_drv = {
+	.driver	= {
+		.name   = "tsc40",
+	},
+	.description    = DRIVER_DESC,
+	.id_table	= tsc_serio_ids,
+	.interrupt      = tsc_interrupt,
+	.connect	= tsc_connect,
+	.disconnect     = tsc_disconnect,
+};
+
+module_serio_driver(tsc_drv);
+
+MODULE_AUTHOR("Sebastian Andrzej Siewior <bigeasy@linutronix.de>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");