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, 44 insertions, 0 deletions

diff --git a/drivers/md/md-cluster.h b/drivers/md/md-cluster.h
new file mode 100644
index 000000000..8fb06d853
--- /dev/null
+++ b/drivers/md/md-cluster.h
@@ -0,0 +1,44 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+
+#ifndef _MD_CLUSTER_H
+#define _MD_CLUSTER_H
+
+#include "md.h"
+
+struct mddev;
+struct md_rdev;
+
+struct md_cluster_operations {
+	struct md_submodule_head head;
+
+	int (*join)(struct mddev *mddev, int nodes);
+	int (*leave)(struct mddev *mddev);
+	int (*slot_number)(struct mddev *mddev);
+	int (*resync_info_update)(struct mddev *mddev, sector_t lo, sector_t hi);
+	int (*resync_start_notify)(struct mddev *mddev);
+	int (*resync_status_get)(struct mddev *mddev);
+	void (*resync_info_get)(struct mddev *mddev, sector_t *lo, sector_t *hi);
+	int (*metadata_update_start)(struct mddev *mddev);
+	int (*metadata_update_finish)(struct mddev *mddev);
+	void (*metadata_update_cancel)(struct mddev *mddev);
+	int (*resync_start)(struct mddev *mddev);
+	int (*resync_finish)(struct mddev *mddev);
+	int (*area_resyncing)(struct mddev *mddev, int direction, sector_t lo, sector_t hi);
+	int (*add_new_disk)(struct mddev *mddev, struct md_rdev *rdev);
+	void (*add_new_disk_cancel)(struct mddev *mddev);
+	int (*new_disk_ack)(struct mddev *mddev, bool ack);
+	int (*remove_disk)(struct mddev *mddev, struct md_rdev *rdev);
+	void (*load_bitmaps)(struct mddev *mddev, int total_slots);
+	int (*gather_bitmaps)(struct md_rdev *rdev);
+	int (*resize_bitmaps)(struct mddev *mddev, sector_t newsize, sector_t oldsize);
+	int (*lock_all_bitmaps)(struct mddev *mddev);
+	void (*unlock_all_bitmaps)(struct mddev *mddev);
+	void (*update_size)(struct mddev *mddev, sector_t old_dev_sectors);
+};
+
+extern int md_setup_cluster(struct mddev *mddev, int nodes);
+extern void md_cluster_stop(struct mddev *mddev);
+extern void md_reload_sb(struct mddev *mddev, int raid_disk);
+
+#endif /* _MD_CLUSTER_H */