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, 29 insertions, 0 deletions

diff --git a/drivers/mfd/cs42l43.h b/drivers/mfd/cs42l43.h
new file mode 100644
index 000000000..a0068f657
--- /dev/null
+++ b/drivers/mfd/cs42l43.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * CS42L43 core driver internal data
+ *
+ * Copyright (C) 2022-2023 Cirrus Logic, Inc. and
+ *                         Cirrus Logic International Semiconductor Ltd.
+ */
+
+#ifndef CS42L43_CORE_INT_H
+#define CS42L43_CORE_INT_H
+
+#define CS42L43_N_DEFAULTS 189
+
+struct dev_pm_ops;
+struct device;
+struct reg_default;
+
+struct cs42l43;
+
+extern const struct dev_pm_ops cs42l43_pm_ops;
+extern const struct reg_default cs42l43_reg_default[CS42L43_N_DEFAULTS];
+
+bool cs42l43_readable_register(struct device *dev, unsigned int reg);
+bool cs42l43_precious_register(struct device *dev, unsigned int reg);
+bool cs42l43_volatile_register(struct device *dev, unsigned int reg);
+
+int cs42l43_dev_probe(struct cs42l43 *cs42l43);
+
+#endif /* CS42L43_CORE_INT_H */