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, 112 insertions, 0 deletions

diff --git a/drivers/hid/hid-pxrc.c b/drivers/hid/hid-pxrc.c
new file mode 100644
index 000000000..71fe0c06d
--- /dev/null
+++ b/drivers/hid/hid-pxrc.c
@@ -0,0 +1,112 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HID driver for PhoenixRC 8-axis flight controller
+ *
+ * Copyright (C) 2022 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+struct pxrc_priv {
+	u8 slider;
+	u8 dial;
+	bool alternate;
+};
+
+static const __u8 pxrc_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, 0x36,        //     Usage (Slider)
+	0x09, 0x31,        //     Usage (Y)
+	0x09, 0x32,        //     Usage (Z)
+	0x09, 0x33,        //     Usage (Rx)
+	0x09, 0x34,        //     Usage (Ry)
+	0x09, 0x35,        //     Usage (Rz)
+	0x09, 0x37,        //     Usage (Dial)
+	0x15, 0x00,        //     Logical Minimum (0)
+	0x26, 0xFF, 0x00,  //     Logical Maximum (255)
+	0x35, 0x00,        //     Physical Minimum (0)
+	0x46, 0xFF, 0x00,  //     Physical Maximum (255)
+	0x75, 0x08,        //     Report Size (8)
+	0x95, 0x08,        //     Report Count (8)
+	0x81, 0x02,        //     Input (Data,Var,Abs,No Wrap,Linear,Preferred State,No Null Position)
+	0xC0,              //   End Collection
+	0xC0,              // End Collection
+};
+
+static const __u8 *pxrc_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+				     unsigned int *rsize)
+{
+	hid_info(hdev, "fixing up PXRC report descriptor\n");
+	*rsize = sizeof(pxrc_rdesc_fixed);
+	return pxrc_rdesc_fixed;
+}
+
+static int pxrc_raw_event(struct hid_device *hdev, struct hid_report *report,
+	 u8 *data, int size)
+{
+	struct pxrc_priv *priv = hid_get_drvdata(hdev);
+
+	if (priv->alternate)
+		priv->slider = data[7];
+	else
+		priv->dial = data[7];
+
+	data[1] = priv->slider;
+	data[7] = priv->dial;
+
+	priv->alternate = !priv->alternate;
+	return 0;
+}
+
+static int pxrc_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int ret;
+	struct pxrc_priv *priv;
+
+	priv = devm_kzalloc(&hdev->dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+	hid_set_drvdata(hdev, priv);
+
+	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 pxrc_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_MULTIPLE_1781, USB_DEVICE_ID_PHOENIXRC) },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(hid, pxrc_devices);
+
+static struct hid_driver pxrc_driver = {
+	.name = "hid-pxrc",
+	.id_table = pxrc_devices,
+	.report_fixup = pxrc_report_fixup,
+	.probe = pxrc_probe,
+	.raw_event = pxrc_raw_event,
+};
+module_hid_driver(pxrc_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("HID driver for PXRC 8-axis flight controller");
+MODULE_LICENSE("GPL");