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, 26 insertions, 0 deletions

diff --git a/io_uring/uring_cmd.h b/io_uring/uring_cmd.h
new file mode 100644
index 000000000..041aef8a8
--- /dev/null
+++ b/io_uring/uring_cmd.h
@@ -0,0 +1,26 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io_uring/cmd.h>
+#include <linux/io_uring_types.h>
+
+struct io_async_cmd {
+	struct iou_vec			vec;
+	struct io_uring_sqe		sqes[2];
+};
+
+int io_uring_cmd(struct io_kiocb *req, unsigned int issue_flags);
+int io_uring_cmd_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);
+void io_uring_cmd_sqe_copy(struct io_kiocb *req);
+void io_uring_cmd_cleanup(struct io_kiocb *req);
+
+bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
+				   struct io_uring_task *tctx, bool cancel_all);
+
+bool io_uring_cmd_post_mshot_cqe32(struct io_uring_cmd *cmd,
+				   unsigned int issue_flags,
+				   struct io_uring_cqe cqe[2]);
+
+void io_cmd_cache_free(const void *entry);
+
+int io_cmd_poll_multishot(struct io_uring_cmd *cmd,
+			  unsigned int issue_flags, __poll_t mask);