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, 319 insertions, 0 deletions

diff --git a/drivers/scsi/arm/queue.c b/drivers/scsi/arm/queue.c
new file mode 100644
index 000000000..797cf4971
--- /dev/null
+++ b/drivers/scsi/arm/queue.c
@@ -0,0 +1,319 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/drivers/acorn/scsi/queue.c: queue handling primitives
+ *
+ *  Copyright (C) 1997-2000 Russell King
+ *
+ *  Changelog:
+ *   15-Sep-1997 RMK	Created.
+ *   11-Oct-1997 RMK	Corrected problem with queue_remove_exclude
+ *			not updating internal linked list properly
+ *			(was causing commands to go missing).
+ *   30-Aug-2000 RMK	Use Linux list handling and spinlocks
+ */
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/list.h>
+#include <linux/init.h>
+
+#include <scsi/scsi.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_eh.h>
+#include <scsi/scsi_tcq.h>
+
+#define DEBUG
+
+typedef struct queue_entry {
+	struct list_head   list;
+	struct scsi_cmnd   *SCpnt;
+#ifdef DEBUG
+	unsigned long	   magic;
+#endif
+} QE_t;
+
+#ifdef DEBUG
+#define QUEUE_MAGIC_FREE	0xf7e1c9a3
+#define QUEUE_MAGIC_USED	0xf7e1cc33
+
+#define SET_MAGIC(q,m)	((q)->magic = (m))
+#define BAD_MAGIC(q,m)	((q)->magic != (m))
+#else
+#define SET_MAGIC(q,m)	do { } while (0)
+#define BAD_MAGIC(q,m)	(0)
+#endif
+
+#include "queue.h"
+
+#define NR_QE	32
+
+/*
+ * Function: void queue_initialise (Queue_t *queue)
+ * Purpose : initialise a queue
+ * Params  : queue - queue to initialise
+ */
+int queue_initialise (Queue_t *queue)
+{
+	unsigned int nqueues = NR_QE;
+	QE_t *q;
+
+	spin_lock_init(&queue->queue_lock);
+	INIT_LIST_HEAD(&queue->head);
+	INIT_LIST_HEAD(&queue->free);
+
+	/*
+	 * If life was easier, then SCpnt would have a
+	 * host-available list head, and we wouldn't
+	 * need to keep free lists or allocate this
+	 * memory.
+	 */
+	queue->alloc = q = kmalloc_objs(QE_t, nqueues);
+	if (q) {
+		for (; nqueues; q++, nqueues--) {
+			SET_MAGIC(q, QUEUE_MAGIC_FREE);
+			q->SCpnt = NULL;
+			list_add(&q->list, &queue->free);
+		}
+	}
+
+	return queue->alloc != NULL;
+}
+
+/*
+ * Function: void queue_free (Queue_t *queue)
+ * Purpose : free a queue
+ * Params  : queue - queue to free
+ */
+void queue_free (Queue_t *queue)
+{
+	if (!list_empty(&queue->head))
+		printk(KERN_WARNING "freeing non-empty queue %p\n", queue);
+	kfree(queue->alloc);
+}
+     
+
+/*
+ * Function: int __queue_add(Queue_t *queue, struct scsi_cmnd *SCpnt, int head)
+ * Purpose : Add a new command onto a queue, adding REQUEST_SENSE to head.
+ * Params  : queue - destination queue
+ *	     SCpnt - command to add
+ *	     head  - add command to head of queue
+ * Returns : 0 on error, !0 on success
+ */
+int __queue_add(Queue_t *queue, struct scsi_cmnd *SCpnt, int head)
+{
+	unsigned long flags;
+	struct list_head *l;
+	QE_t *q;
+	int ret = 0;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	if (list_empty(&queue->free))
+		goto empty;
+
+	l = queue->free.next;
+	list_del(l);
+
+	q = list_entry(l, QE_t, list);
+	BUG_ON(BAD_MAGIC(q, QUEUE_MAGIC_FREE));
+
+	SET_MAGIC(q, QUEUE_MAGIC_USED);
+	q->SCpnt = SCpnt;
+
+	if (head)
+		list_add(l, &queue->head);
+	else
+		list_add_tail(l, &queue->head);
+
+	ret = 1;
+empty:
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+	return ret;
+}
+
+static struct scsi_cmnd *__queue_remove(Queue_t *queue, struct list_head *ent)
+{
+	QE_t *q;
+
+	/*
+	 * Move the entry from the "used" list onto the "free" list
+	 */
+	list_del(ent);
+	q = list_entry(ent, QE_t, list);
+	BUG_ON(BAD_MAGIC(q, QUEUE_MAGIC_USED));
+
+	SET_MAGIC(q, QUEUE_MAGIC_FREE);
+	list_add(ent, &queue->free);
+
+	return q->SCpnt;
+}
+
+/*
+ * Function: struct scsi_cmnd *queue_remove_exclude (queue, exclude)
+ * Purpose : remove a SCSI command from a queue
+ * Params  : queue   - queue to remove command from
+ *	     exclude - bit array of target&lun which is busy
+ * Returns : struct scsi_cmnd if successful (and a reference), or NULL if no command available
+ */
+struct scsi_cmnd *queue_remove_exclude(Queue_t *queue, unsigned long *exclude)
+{
+	unsigned long flags;
+	struct list_head *l;
+	struct scsi_cmnd *SCpnt = NULL;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	list_for_each(l, &queue->head) {
+		QE_t *q = list_entry(l, QE_t, list);
+		if (!test_bit(q->SCpnt->device->id * 8 +
+			      (u8)(q->SCpnt->device->lun & 0x7), exclude)) {
+			SCpnt = __queue_remove(queue, l);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+
+	return SCpnt;
+}
+
+/*
+ * 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
+ */
+struct scsi_cmnd *queue_remove(Queue_t *queue)
+{
+	unsigned long flags;
+	struct scsi_cmnd *SCpnt = NULL;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	if (!list_empty(&queue->head))
+		SCpnt = __queue_remove(queue, queue->head.next);
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+
+	return SCpnt;
+}
+
+/*
+ * 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
+ */
+struct scsi_cmnd *queue_remove_tgtluntag(Queue_t *queue, int target, int lun,
+					 int tag)
+{
+	unsigned long flags;
+	struct list_head *l;
+	struct scsi_cmnd *SCpnt = NULL;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	list_for_each(l, &queue->head) {
+		QE_t *q = list_entry(l, QE_t, list);
+		if (q->SCpnt->device->id == target && q->SCpnt->device->lun == lun &&
+		    scsi_cmd_to_rq(q->SCpnt)->tag == tag) {
+			SCpnt = __queue_remove(queue, l);
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+
+	return SCpnt;
+}
+
+/*
+ * 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
+ */
+void queue_remove_all_target(Queue_t *queue, int target)
+{
+	unsigned long flags;
+	struct list_head *l;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	list_for_each(l, &queue->head) {
+		QE_t *q = list_entry(l, QE_t, list);
+		if (q->SCpnt->device->id == target)
+			__queue_remove(queue, l);
+	}
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+}
+
+/*
+ * 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
+ */
+int queue_probetgtlun (Queue_t *queue, int target, int lun)
+{
+	unsigned long flags;
+	struct list_head *l;
+	int found = 0;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	list_for_each(l, &queue->head) {
+		QE_t *q = list_entry(l, QE_t, list);
+		if (q->SCpnt->device->id == target && q->SCpnt->device->lun == lun) {
+			found = 1;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+
+	return found;
+}
+
+/*
+ * 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)
+{
+	unsigned long flags;
+	struct list_head *l;
+	int found = 0;
+
+	spin_lock_irqsave(&queue->queue_lock, flags);
+	list_for_each(l, &queue->head) {
+		QE_t *q = list_entry(l, QE_t, list);
+		if (q->SCpnt == SCpnt) {
+			__queue_remove(queue, l);
+			found = 1;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&queue->queue_lock, flags);
+
+	return found;
+}
+
+EXPORT_SYMBOL(queue_initialise);
+EXPORT_SYMBOL(queue_free);
+EXPORT_SYMBOL(__queue_add);
+EXPORT_SYMBOL(queue_remove);
+EXPORT_SYMBOL(queue_remove_exclude);
+EXPORT_SYMBOL(queue_remove_tgtluntag);
+EXPORT_SYMBOL(queue_remove_cmd);
+EXPORT_SYMBOL(queue_remove_all_target);
+EXPORT_SYMBOL(queue_probetgtlun);
+
+MODULE_AUTHOR("Russell King");
+MODULE_DESCRIPTION("SCSI command queueing");
+MODULE_LICENSE("GPL");