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, 104 insertions, 0 deletions

diff --git a/drivers/scsi/arm/queue.h b/drivers/scsi/arm/queue.h
new file mode 100644
index 000000000..cb51379dc
--- /dev/null
+++ b/drivers/scsi/arm/queue.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ *  linux/drivers/acorn/scsi/queue.h: queue handling
+ *
+ *  Copyright (C) 1997 Russell King
+ */
+#ifndef QUEUE_H
+#define QUEUE_H
+
+typedef struct {
+	struct list_head head;
+	struct list_head free;
+	spinlock_t queue_lock;
+	void *alloc;			/* start of allocated mem */
+} Queue_t;
+
+/*
+ * Function: void queue_initialise (Queue_t *queue)
+ * Purpose : initialise a queue
+ * Params  : queue - queue to initialise
+ */
+extern int queue_initialise (Queue_t *queue);
+
+/*
+ * Function: void queue_free (Queue_t *queue)
+ * Purpose : free a queue
+ * Params  : queue - queue to free
+ */
+extern void queue_free (Queue_t *queue);
+
+/*
+ * Function: struct scsi_cmnd *queue_remove (queue)
+ * Purpose : removes first SCSI command from a queue
+ * Params  : queue   - queue to remove command from
+ * Returns : struct scsi_cmnd if successful (and a reference), or NULL if no command available
+ */
+extern struct scsi_cmnd *queue_remove (Queue_t *queue);
+
+/*
+ * Function: struct scsi_cmnd *queue_remove_exclude_ref (queue, exclude)
+ * Purpose : remove a SCSI command from a queue
+ * Params  : queue   - queue to remove command from
+ *	     exclude - array of busy LUNs
+ * Returns : struct scsi_cmnd if successful (and a reference), or NULL if no command available
+ */
+extern struct scsi_cmnd *queue_remove_exclude(Queue_t *queue,
+					      unsigned long *exclude);
+
+#define queue_add_cmd_ordered(queue,SCpnt) \
+	__queue_add(queue,SCpnt,(SCpnt)->cmnd[0] == REQUEST_SENSE)
+#define queue_add_cmd_tail(queue,SCpnt) \
+	__queue_add(queue,SCpnt,0)
+/*
+ * Function: int __queue_add(Queue_t *queue, struct scsi_cmnd *SCpnt, int head)
+ * Purpose : Add a new command onto a queue
+ * Params  : queue - destination queue
+ *	     SCpnt - command to add
+ *	     head  - add command to head of queue
+ * Returns : 0 on error, !0 on success
+ */
+extern int __queue_add(Queue_t *queue, struct scsi_cmnd *SCpnt, int head);
+
+/*
+ * Function: struct scsi_cmnd *queue_remove_tgtluntag (queue, target, lun, tag)
+ * Purpose : remove a SCSI command from the queue for a specified target/lun/tag
+ * Params  : queue  - queue to remove command from
+ *	     target - target that we want
+ *	     lun    - lun on device
+ *	     tag    - tag on device
+ * Returns : struct scsi_cmnd if successful, or NULL if no command satisfies requirements
+ */
+extern struct scsi_cmnd *queue_remove_tgtluntag(Queue_t *queue, int target,
+						int lun, int tag);
+
+/*
+ * Function: queue_remove_all_target(queue, target)
+ * Purpose : remove all SCSI commands from the queue for a specified target
+ * Params  : queue  - queue to remove command from
+ *           target - target device id
+ * Returns : nothing
+ */
+extern void queue_remove_all_target(Queue_t *queue, int target);
+
+/*
+ * Function: int queue_probetgtlun (queue, target, lun)
+ * Purpose : check to see if we have a command in the queue for the specified
+ *	     target/lun.
+ * Params  : queue  - queue to look in
+ *	     target - target we want to probe
+ *	     lun    - lun on target
+ * Returns : 0 if not found, != 0 if found
+ */
+extern int queue_probetgtlun (Queue_t *queue, int target, int lun);
+
+/*
+ * Function: int queue_remove_cmd (Queue_t *queue, struct scsi_cmnd *SCpnt)
+ * Purpose : remove a specific command from the queues
+ * Params  : queue - queue to look in
+ *	     SCpnt - command to find
+ * Returns : 0 if not found
+ */
+int queue_remove_cmd(Queue_t *queue, struct scsi_cmnd *SCpnt);
+
+#endif /* QUEUE_H */