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, 91 insertions, 0 deletions

diff --git a/drivers/hid/hid-vrc2.c b/drivers/hid/hid-vrc2.c
new file mode 100644
index 000000000..7dc41e92f
--- /dev/null
+++ b/drivers/hid/hid-vrc2.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for VRC-2 2-axis Car controller
+ *
+ * Copyright (C) 2022 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+/*
+ * VID/PID are probably "borrowed", so keep them locally and
+ * do not populate hid-ids.h with those.
+ */
+#define USB_VENDOR_ID_VRC2	(0x07c0)
+#define USB_DEVICE_ID_VRC2	(0x1125)
+
+static const __u8 vrc2_rdesc_fixed[] = {
+	0x05, 0x01,        // Usage Page (Generic Desktop Ctrls)
+	0x09, 0x04,        // Usage (Joystick)
+	0xA1, 0x01,        // Collection (Application)
+	0x09, 0x01,        //   Usage (Pointer)
+	0xA1, 0x00,        //   Collection (Physical)
+	0x09, 0x30,        //     Usage (X)
+	0x09, 0x31,        //     Usage (Y)
+	0x15, 0x00,        //     Logical Minimum (0)
+	0x26, 0xFF, 0x07,  //     Logical Maximum (2047)
+	0x35, 0x00,        //     Physical Minimum (0)
+	0x46, 0xFF, 0x00,  //     Physical Maximum (255)
+	0x75, 0x10,        //     Report Size (16)
+	0x95, 0x02,        //     Report Count (2)
+	0x81, 0x02,        //     Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+	0xC0,              //   End Collection
+	0x75, 0x08,        //   Report Size (8)
+	0x95, 0x03,        //   Report Count (3)
+	0x81, 0x03,        //   Input (Cnst,Var,Abs)
+	0xC0,              // End Collection
+};
+
+static const __u8 *vrc2_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+				     unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up VRC-2 report descriptor\n");
+	*rsize = sizeof(vrc2_rdesc_fixed);
+	return vrc2_rdesc_fixed;
+}
+
+static int vrc2_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+
+	/*
+	 * The device gives us 2 separate USB endpoints.
+	 * One of those (the one with report descriptor size of 23) is just bogus so ignore it
+	 */
+	if (hdev->dev_rsize == 23)
+		return -ENODEV;
+
+	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 vrc2_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_VRC2, USB_DEVICE_ID_VRC2) },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(hid, vrc2_devices);
+
+static struct hid_driver vrc2_driver = {
+	.name = "vrc2",
+	.id_table = vrc2_devices,
+	.report_fixup = vrc2_report_fixup,
+	.probe = vrc2_probe,
+};
+module_hid_driver(vrc2_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("HID driver for VRC-2 2-axis Car controller");
+MODULE_LICENSE("GPL");