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, 274 insertions, 0 deletions

diff --git a/drivers/bluetooth/hci_h4.c b/drivers/bluetooth/hci_h4.c
new file mode 100644
index 000000000..767372707
--- /dev/null
+++ b/drivers/bluetooth/hci_h4.c
@@ -0,0 +1,274 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *
+ *  Bluetooth HCI UART driver
+ *
+ *  Copyright (C) 2000-2001  Qualcomm Incorporated
+ *  Copyright (C) 2002-2003  Maxim Krasnyansky <maxk@qualcomm.com>
+ *  Copyright (C) 2004-2005  Marcel Holtmann <marcel@holtmann.org>
+ */
+
+#include <linux/module.h>
+
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/interrupt.h>
+#include <linux/ptrace.h>
+#include <linux/poll.h>
+
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/signal.h>
+#include <linux/ioctl.h>
+#include <linux/skbuff.h>
+#include <linux/unaligned.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "hci_uart.h"
+
+struct h4_struct {
+	struct sk_buff *rx_skb;
+	struct sk_buff_head txq;
+};
+
+/* Initialize protocol */
+static int h4_open(struct hci_uart *hu)
+{
+	struct h4_struct *h4;
+
+	BT_DBG("hu %p", hu);
+
+	h4 = kzalloc_obj(*h4);
+	if (!h4)
+		return -ENOMEM;
+
+	skb_queue_head_init(&h4->txq);
+
+	hu->priv = h4;
+	return 0;
+}
+
+/* Flush protocol data */
+static int h4_flush(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p", hu);
+
+	skb_queue_purge(&h4->txq);
+
+	return 0;
+}
+
+/* Close protocol */
+static int h4_close(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p", hu);
+
+	skb_queue_purge(&h4->txq);
+
+	kfree_skb(h4->rx_skb);
+
+	hu->priv = NULL;
+	kfree(h4);
+
+	return 0;
+}
+
+/* Enqueue frame for transmission (padding, crc, etc) */
+static int h4_enqueue(struct hci_uart *hu, struct sk_buff *skb)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	BT_DBG("hu %p skb %p", hu, skb);
+
+	/* Prepend skb with frame type */
+	memcpy(skb_push(skb, 1), &hci_skb_pkt_type(skb), 1);
+	skb_queue_tail(&h4->txq, skb);
+
+	return 0;
+}
+
+static const struct h4_recv_pkt h4_recv_pkts[] = {
+	{ H4_RECV_ACL,   .recv = hci_recv_frame },
+	{ H4_RECV_SCO,   .recv = hci_recv_frame },
+	{ H4_RECV_EVENT, .recv = hci_recv_frame },
+	{ H4_RECV_ISO,   .recv = hci_recv_frame },
+};
+
+/* Recv data */
+static int h4_recv(struct hci_uart *hu, const void *data, int count)
+{
+	struct h4_struct *h4 = hu->priv;
+
+	if (!h4)
+		return -ENODEV;
+
+	h4->rx_skb = h4_recv_buf(hu, h4->rx_skb, data, count,
+				 h4_recv_pkts, ARRAY_SIZE(h4_recv_pkts));
+	if (IS_ERR(h4->rx_skb)) {
+		int err = PTR_ERR(h4->rx_skb);
+		bt_dev_err(hu->hdev, "Frame reassembly failed (%d)", err);
+		h4->rx_skb = NULL;
+		return err;
+	}
+
+	return count;
+}
+
+static struct sk_buff *h4_dequeue(struct hci_uart *hu)
+{
+	struct h4_struct *h4 = hu->priv;
+	return skb_dequeue(&h4->txq);
+}
+
+static const struct hci_uart_proto h4p = {
+	.id		= HCI_UART_H4,
+	.name		= "H4",
+	.open		= h4_open,
+	.close		= h4_close,
+	.recv		= h4_recv,
+	.enqueue	= h4_enqueue,
+	.dequeue	= h4_dequeue,
+	.flush		= h4_flush,
+};
+
+int __init h4_init(void)
+{
+	return hci_uart_register_proto(&h4p);
+}
+
+int __exit h4_deinit(void)
+{
+	return hci_uart_unregister_proto(&h4p);
+}
+
+struct sk_buff *h4_recv_buf(struct hci_uart *hu, struct sk_buff *skb,
+			    const unsigned char *buffer, int count,
+			    const struct h4_recv_pkt *pkts, int pkts_count)
+{
+	u8 alignment = hu->alignment ? hu->alignment : 1;
+	struct hci_dev *hdev = hu->hdev;
+
+	/* Check for error from previous call */
+	if (IS_ERR(skb))
+		skb = NULL;
+
+	while (count) {
+		int i, len;
+
+		/* remove padding bytes from buffer */
+		for (; hu->padding && count > 0; hu->padding--) {
+			count--;
+			buffer++;
+		}
+		if (!count)
+			break;
+
+		if (!skb) {
+			for (i = 0; i < pkts_count; i++) {
+				if (buffer[0] != (&pkts[i])->type)
+					continue;
+
+				skb = bt_skb_alloc((&pkts[i])->maxlen,
+						   GFP_ATOMIC);
+				if (!skb)
+					return ERR_PTR(-ENOMEM);
+
+				hci_skb_pkt_type(skb) = (&pkts[i])->type;
+				hci_skb_expect(skb) = (&pkts[i])->hlen;
+				break;
+			}
+
+			/* Check for invalid packet type */
+			if (!skb)
+				return ERR_PTR(-EILSEQ);
+
+			count -= 1;
+			buffer += 1;
+		}
+
+		len = min_t(uint, hci_skb_expect(skb) - skb->len, count);
+		skb_put_data(skb, buffer, len);
+
+		count -= len;
+		buffer += len;
+
+		/* Check for partial packet */
+		if (skb->len < hci_skb_expect(skb))
+			continue;
+
+		for (i = 0; i < pkts_count; i++) {
+			if (hci_skb_pkt_type(skb) == (&pkts[i])->type)
+				break;
+		}
+
+		if (i >= pkts_count) {
+			kfree_skb(skb);
+			return ERR_PTR(-EILSEQ);
+		}
+
+		if (skb->len == (&pkts[i])->hlen) {
+			u16 dlen;
+
+			switch ((&pkts[i])->lsize) {
+			case 0:
+				/* No variable data length */
+				dlen = 0;
+				break;
+			case 1:
+				/* Single octet variable length */
+				dlen = skb->data[(&pkts[i])->loff];
+				hci_skb_expect(skb) += dlen;
+
+				if (skb_tailroom(skb) < dlen) {
+					kfree_skb(skb);
+					return ERR_PTR(-EMSGSIZE);
+				}
+				break;
+			case 2:
+				/* Double octet variable length */
+				dlen = get_unaligned_le16(skb->data +
+							  (&pkts[i])->loff);
+				hci_skb_expect(skb) += dlen;
+
+				if (skb_tailroom(skb) < dlen) {
+					kfree_skb(skb);
+					return ERR_PTR(-EMSGSIZE);
+				}
+				break;
+			default:
+				/* Unsupported variable length */
+				kfree_skb(skb);
+				return ERR_PTR(-EILSEQ);
+			}
+
+			if (!dlen) {
+				hu->padding = (skb->len + 1) % alignment;
+				hu->padding = (alignment - hu->padding) % alignment;
+
+				/* No more data, complete frame */
+				(&pkts[i])->recv(hdev, skb);
+				skb = NULL;
+			}
+		} else {
+			hu->padding = (skb->len + 1) % alignment;
+			hu->padding = (alignment - hu->padding) % alignment;
+
+			/* Complete frame */
+			(&pkts[i])->recv(hdev, skb);
+			skb = NULL;
+		}
+	}
+
+	return skb;
+}
+EXPORT_SYMBOL_GPL(h4_recv_buf);