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, 50 insertions, 0 deletions

diff --git a/security/lsm.h b/security/lsm.h
new file mode 100644
index 000000000..32f808ad4
--- /dev/null
+++ b/security/lsm.h
@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * LSM functions
+ */
+
+#ifndef _LSM_H_
+#define _LSM_H_
+
+#include <linux/printk.h>
+#include <linux/lsm_hooks.h>
+#include <linux/lsm_count.h>
+
+/* LSM debugging */
+extern bool lsm_debug;
+#define lsm_pr(...)		pr_info(__VA_ARGS__)
+#define lsm_pr_cont(...)	pr_cont(__VA_ARGS__)
+#define lsm_pr_dbg(...)							\
+	do {								\
+		if (lsm_debug)						\
+			pr_info(__VA_ARGS__);				\
+	} while (0)
+
+/* List of configured LSMs */
+extern unsigned int lsm_active_cnt;
+extern const struct lsm_id *lsm_idlist[];
+
+/* LSM blob configuration */
+extern struct lsm_blob_sizes blob_sizes;
+
+/* LSM blob caches */
+extern struct kmem_cache *lsm_file_cache;
+extern struct kmem_cache *lsm_backing_file_cache;
+extern struct kmem_cache *lsm_inode_cache;
+
+/* LSM blob allocators */
+int lsm_cred_alloc(struct cred *cred, gfp_t gfp);
+int lsm_task_alloc(struct task_struct *task);
+
+/* LSM framework initializers */
+
+#ifdef CONFIG_SECURITYFS
+int securityfs_init(void);
+#else
+static inline int securityfs_init(void)
+{
+	return 0;
+}
+#endif /* CONFIG_SECURITYFS */
+
+#endif /* _LSM_H_ */