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, 45 insertions, 0 deletions

diff --git a/drivers/hid/hid-macally.c b/drivers/hid/hid-macally.c
new file mode 100644
index 000000000..fe7576458
--- /dev/null
+++ b/drivers/hid/hid-macally.c
@@ -0,0 +1,45 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  HID driver for quirky Macally devices
+ *
+ *  Copyright (c) 2019 Alex Henrie <alexhenrie24@gmail.com>
+ */
+
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+MODULE_AUTHOR("Alex Henrie <alexhenrie24@gmail.com>");
+MODULE_DESCRIPTION("Macally devices");
+MODULE_LICENSE("GPL");
+
+/*
+ * The Macally ikey keyboard says that its logical and usage maximums are both
+ * 101, but the power key is 102 and the equals key is 103
+ */
+static const __u8 *macally_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+					unsigned int *rsize)
+{
+	if (*rsize >= 60 && rdesc[53] == 0x65 && rdesc[59] == 0x65) {
+		hid_info(hdev,
+			"fixing up Macally ikey keyboard report descriptor\n");
+		rdesc[53] = rdesc[59] = 0x67;
+	}
+	return rdesc;
+}
+
+static const struct hid_device_id macally_id_table[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_SOLID_YEAR,
+			 USB_DEVICE_ID_MACALLY_IKEY_KEYBOARD) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, macally_id_table);
+
+static struct hid_driver macally_driver = {
+	.name			= "macally",
+	.id_table		= macally_id_table,
+	.report_fixup		= macally_report_fixup,
+};
+
+module_hid_driver(macally_driver);