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, 74 insertions, 0 deletions

diff --git a/drivers/hid/hid-primax.c b/drivers/hid/hid-primax.c
new file mode 100644
index 000000000..8db054280
--- /dev/null
+++ b/drivers/hid/hid-primax.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * HID driver for primax and similar keyboards with in-band modifiers
+ *
+ * Copyright 2011 Google Inc. All Rights Reserved
+ *
+ * Author:
+ *	Terry Lambert <tlambert@google.com>
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static int px_raw_event(struct hid_device *hid, struct hid_report *report,
+	 u8 *data, int size)
+{
+	int idx = size;
+
+	switch (report->id) {
+	case 0:		/* keyboard input */
+		/*
+		 * Convert in-band modifier key values into out of band
+		 * modifier bits and pull the key strokes from the report.
+		 * Thus a report data set which looked like:
+		 *
+		 * [00][00][E0][30][00][00][00][00]
+		 * (no modifier bits + "Left Shift" key + "1" key)
+		 *
+		 * Would be converted to:
+		 *
+		 * [01][00][00][30][00][00][00][00]
+		 * (Left Shift modifier bit + "1" key)
+		 *
+		 * As long as it's in the size range, the upper level
+		 * drivers don't particularly care if there are in-band
+		 * 0-valued keys, so they don't stop parsing.
+		 */
+		while (--idx > 1) {
+			if (data[idx] < 0xE0 || data[idx] > 0xE7)
+				continue;
+			data[0] |= (1 << (data[idx] - 0xE0));
+			data[idx] = 0;
+		}
+		hid_report_raw_event(hid, HID_INPUT_REPORT, data, size, size, 0);
+		return 1;
+
+	default:	/* unknown report */
+		/* Unknown report type; pass upstream */
+		hid_info(hid, "unknown report type %d\n", report->id);
+		break;
+	}
+
+	return 0;
+}
+
+static const struct hid_device_id px_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_PRIMAX, USB_DEVICE_ID_PRIMAX_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, px_devices);
+
+static struct hid_driver px_driver = {
+	.name = "primax",
+	.id_table = px_devices,
+	.raw_event = px_raw_event,
+};
+module_hid_driver(px_driver);
+
+MODULE_AUTHOR("Terry Lambert <tlambert@google.com>");
+MODULE_DESCRIPTION("HID driver for primax and similar keyboards with in-band modifiers");
+MODULE_LICENSE("GPL");