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, 90 insertions, 0 deletions

diff --git a/drivers/acpi/hed.c b/drivers/acpi/hed.c
new file mode 100644
index 000000000..48562f53d
--- /dev/null
+++ b/drivers/acpi/hed.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ACPI Hardware Error Device (PNP0C33) Driver
+ *
+ * Copyright (C) 2010, Intel Corp.
+ *	Author: Huang Ying <ying.huang@intel.com>
+ *
+ * ACPI Hardware Error Device is used to report some hardware errors
+ * notified via SCI, mainly the corrected errors.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/acpi.h>
+#include <linux/platform_device.h>
+#include <acpi/hed.h>
+
+static const struct acpi_device_id acpi_hed_ids[] = {
+	{"PNP0C33", 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, acpi_hed_ids);
+
+static bool hed_present;
+
+static BLOCKING_NOTIFIER_HEAD(acpi_hed_notify_list);
+
+int register_acpi_hed_notifier(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&acpi_hed_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(register_acpi_hed_notifier);
+
+void unregister_acpi_hed_notifier(struct notifier_block *nb)
+{
+	blocking_notifier_chain_unregister(&acpi_hed_notify_list, nb);
+}
+EXPORT_SYMBOL_GPL(unregister_acpi_hed_notifier);
+
+/*
+ * SCI to report hardware error is forwarded to the listeners of HED,
+ * it is used by HEST Generic Hardware Error Source with notify type
+ * SCI.
+ */
+static void acpi_hed_notify(acpi_handle handle, u32 event, void *data)
+{
+	blocking_notifier_call_chain(&acpi_hed_notify_list, 0, NULL);
+}
+
+static int acpi_hed_probe(struct platform_device *pdev)
+{
+	int err;
+
+	/* Only one hardware error device */
+	if (hed_present)
+		return -EINVAL;
+
+	err = devm_acpi_install_notify_handler(&pdev->dev, ACPI_DEVICE_NOTIFY,
+					       acpi_hed_notify, NULL);
+	if (err)
+		return err;
+
+	hed_present = true;
+	return 0;
+}
+
+static void acpi_hed_remove(struct platform_device *pdev)
+{
+	hed_present = false;
+}
+
+static struct platform_driver acpi_hed_driver = {
+	.probe = acpi_hed_probe,
+	.remove = acpi_hed_remove,
+	.driver = {
+		.name = "acpi-hardware-error-device",
+		.acpi_match_table = acpi_hed_ids,
+	},
+};
+
+static int __init acpi_hed_driver_init(void)
+{
+	return platform_driver_register(&acpi_hed_driver);
+}
+subsys_initcall(acpi_hed_driver_init);
+
+MODULE_AUTHOR("Huang Ying");
+MODULE_DESCRIPTION("ACPI Hardware Error Device Driver");
+MODULE_LICENSE("GPL");