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, 59 insertions, 0 deletions

diff --git a/tools/testing/radix-tree/test.h b/tools/testing/radix-tree/test.h
new file mode 100644
index 000000000..7ef7067e9
--- /dev/null
+++ b/tools/testing/radix-tree/test.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/gfp.h>
+#include <linux/types.h>
+#include <linux/radix-tree.h>
+#include <linux/rcupdate.h>
+
+struct item {
+	struct rcu_head	rcu_head;
+	unsigned long index;
+	unsigned int order;
+};
+
+struct item *item_create(unsigned long index, unsigned int order);
+int item_insert(struct radix_tree_root *root, unsigned long index);
+void item_sanity(struct item *item, unsigned long index);
+void item_free(struct item *item, unsigned long index);
+int item_delete(struct radix_tree_root *root, unsigned long index);
+int item_delete_rcu(struct xarray *xa, unsigned long index);
+struct item *item_lookup(struct radix_tree_root *root, unsigned long index);
+
+void item_check_present(struct radix_tree_root *root, unsigned long index);
+void item_check_absent(struct radix_tree_root *root, unsigned long index);
+void item_gang_check_present(struct radix_tree_root *root,
+			unsigned long start, unsigned long nr,
+			int chunk, int hop);
+void item_full_scan(struct radix_tree_root *root, unsigned long start,
+			unsigned long nr, int chunk);
+void item_kill_tree(struct radix_tree_root *root);
+
+int tag_tagged_items(struct xarray *, unsigned long start, unsigned long end,
+		unsigned batch, xa_mark_t iftag, xa_mark_t thentag);
+
+void xarray_tests(void);
+void tag_check(void);
+void multiorder_checks(void);
+void iteration_test(unsigned order, unsigned duration);
+void iteration_test2(unsigned duration);
+void benchmark(void);
+void idr_checks(void);
+void ida_tests(void);
+
+struct item *
+item_tag_set(struct radix_tree_root *root, unsigned long index, int tag);
+struct item *
+item_tag_clear(struct radix_tree_root *root, unsigned long index, int tag);
+int item_tag_get(struct radix_tree_root *root, unsigned long index, int tag);
+void tree_verify_min_height(struct radix_tree_root *root, int maxindex);
+void verify_tag_consistency(struct radix_tree_root *root, unsigned int tag);
+
+extern int nr_allocated;
+
+/* Normally private parts of lib/radix-tree.c */
+struct radix_tree_node *entry_to_node(void *ptr);
+void radix_tree_dump(struct radix_tree_root *root);
+int root_tag_get(struct radix_tree_root *root, unsigned int tag);
+unsigned long node_maxindex(struct radix_tree_node *);
+unsigned long shift_maxindex(unsigned int shift);
+int radix_tree_cpu_dead(unsigned int cpu);
+extern struct radix_tree_preload radix_tree_preloads;