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, 306 insertions, 0 deletions

diff --git a/net/ipv4/xfrm4_protocol.c b/net/ipv4/xfrm4_protocol.c
new file mode 100644
index 000000000..4ee624d8e
--- /dev/null
+++ b/net/ipv4/xfrm4_protocol.c
@@ -0,0 +1,306 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* xfrm4_protocol.c - Generic xfrm protocol multiplexer.
+ *
+ * Copyright (C) 2013 secunet Security Networks AG
+ *
+ * Author:
+ * Steffen Klassert <steffen.klassert@secunet.com>
+ *
+ * Based on:
+ * net/ipv4/tunnel4.c
+ */
+
+#include <linux/init.h>
+#include <linux/mutex.h>
+#include <linux/skbuff.h>
+#include <net/icmp.h>
+#include <net/ip.h>
+#include <net/protocol.h>
+#include <net/xfrm.h>
+
+static struct xfrm4_protocol __rcu *esp4_handlers __read_mostly;
+static struct xfrm4_protocol __rcu *ah4_handlers __read_mostly;
+static struct xfrm4_protocol __rcu *ipcomp4_handlers __read_mostly;
+static DEFINE_MUTEX(xfrm4_protocol_mutex);
+
+static inline struct xfrm4_protocol __rcu **proto_handlers(u8 protocol)
+{
+	switch (protocol) {
+	case IPPROTO_ESP:
+		return &esp4_handlers;
+	case IPPROTO_AH:
+		return &ah4_handlers;
+	case IPPROTO_COMP:
+		return &ipcomp4_handlers;
+	}
+
+	return NULL;
+}
+
+#define for_each_protocol_rcu(head, handler)		\
+	for (handler = rcu_dereference(head);		\
+	     handler != NULL;				\
+	     handler = rcu_dereference(handler->next))	\
+
+static int xfrm4_rcv_cb(struct sk_buff *skb, u8 protocol, int err)
+{
+	int ret;
+	struct xfrm4_protocol *handler;
+	struct xfrm4_protocol __rcu **head = proto_handlers(protocol);
+
+	if (!head)
+		return 0;
+
+	for_each_protocol_rcu(*head, handler)
+		if ((ret = handler->cb_handler(skb, err)) <= 0)
+			return ret;
+
+	return 0;
+}
+
+int xfrm4_rcv_encap(struct sk_buff *skb, int nexthdr, __be32 spi,
+		    int encap_type)
+{
+	int ret;
+	struct xfrm4_protocol *handler;
+	struct xfrm4_protocol __rcu **head = proto_handlers(nexthdr);
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+	XFRM_SPI_SKB_CB(skb)->family = AF_INET;
+	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct iphdr, daddr);
+
+	if (!head)
+		goto out;
+
+	if (!skb_dst(skb)) {
+		const struct iphdr *iph = ip_hdr(skb);
+
+		if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
+					 ip4h_dscp(iph), skb->dev))
+			goto drop;
+	}
+
+	for_each_protocol_rcu(*head, handler)
+		if ((ret = handler->input_handler(skb, nexthdr, spi, encap_type)) != -EINVAL)
+			return ret;
+
+out:
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+
+drop:
+	kfree_skb(skb);
+	return 0;
+}
+EXPORT_SYMBOL(xfrm4_rcv_encap);
+
+static int xfrm4_esp_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm4_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
+	for_each_protocol_rcu(esp4_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static int xfrm4_esp_err(struct sk_buff *skb, u32 info)
+{
+	struct xfrm4_protocol *handler;
+
+	for_each_protocol_rcu(esp4_handlers, handler)
+		if (!handler->err_handler(skb, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static int xfrm4_ah_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm4_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
+	for_each_protocol_rcu(ah4_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static int xfrm4_ah_err(struct sk_buff *skb, u32 info)
+{
+	struct xfrm4_protocol *handler;
+
+	for_each_protocol_rcu(ah4_handlers, handler)
+		if (!handler->err_handler(skb, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static int xfrm4_ipcomp_rcv(struct sk_buff *skb)
+{
+	int ret;
+	struct xfrm4_protocol *handler;
+
+	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip4 = NULL;
+
+	for_each_protocol_rcu(ipcomp4_handlers, handler)
+		if ((ret = handler->handler(skb)) != -EINVAL)
+			return ret;
+
+	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
+
+	kfree_skb(skb);
+	return 0;
+}
+
+static int xfrm4_ipcomp_err(struct sk_buff *skb, u32 info)
+{
+	struct xfrm4_protocol *handler;
+
+	for_each_protocol_rcu(ipcomp4_handlers, handler)
+		if (!handler->err_handler(skb, info))
+			return 0;
+
+	return -ENOENT;
+}
+
+static const struct net_protocol esp4_protocol = {
+	.handler	=	xfrm4_esp_rcv,
+	.err_handler	=	xfrm4_esp_err,
+	.no_policy	=	1,
+};
+
+static const struct net_protocol ah4_protocol = {
+	.handler	=	xfrm4_ah_rcv,
+	.err_handler	=	xfrm4_ah_err,
+	.no_policy	=	1,
+};
+
+static const struct net_protocol ipcomp4_protocol = {
+	.handler	=	xfrm4_ipcomp_rcv,
+	.err_handler	=	xfrm4_ipcomp_err,
+	.no_policy	=	1,
+};
+
+static const struct xfrm_input_afinfo xfrm4_input_afinfo = {
+	.family		=	AF_INET,
+	.callback	=	xfrm4_rcv_cb,
+};
+
+static inline const struct net_protocol *netproto(unsigned char protocol)
+{
+	switch (protocol) {
+	case IPPROTO_ESP:
+		return &esp4_protocol;
+	case IPPROTO_AH:
+		return &ah4_protocol;
+	case IPPROTO_COMP:
+		return &ipcomp4_protocol;
+	}
+
+	return NULL;
+}
+
+int xfrm4_protocol_register(struct xfrm4_protocol *handler,
+			    unsigned char protocol)
+{
+	struct xfrm4_protocol __rcu **pprev;
+	struct xfrm4_protocol *t;
+	bool add_netproto = false;
+	int ret = -EEXIST;
+	int priority = handler->priority;
+
+	if (!proto_handlers(protocol) || !netproto(protocol))
+		return -EINVAL;
+
+	mutex_lock(&xfrm4_protocol_mutex);
+
+	if (!rcu_dereference_protected(*proto_handlers(protocol),
+				       lockdep_is_held(&xfrm4_protocol_mutex)))
+		add_netproto = true;
+
+	for (pprev = proto_handlers(protocol);
+	     (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&xfrm4_protocol_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t->priority < priority)
+			break;
+		if (t->priority == priority)
+			goto err;
+	}
+
+	handler->next = *pprev;
+	rcu_assign_pointer(*pprev, handler);
+
+	ret = 0;
+
+err:
+	mutex_unlock(&xfrm4_protocol_mutex);
+
+	if (add_netproto) {
+		if (inet_add_protocol(netproto(protocol), protocol)) {
+			pr_err("%s: can't add protocol\n", __func__);
+			ret = -EAGAIN;
+		}
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm4_protocol_register);
+
+int xfrm4_protocol_deregister(struct xfrm4_protocol *handler,
+			      unsigned char protocol)
+{
+	struct xfrm4_protocol __rcu **pprev;
+	struct xfrm4_protocol *t;
+	int ret = -ENOENT;
+
+	if (!proto_handlers(protocol) || !netproto(protocol))
+		return -EINVAL;
+
+	mutex_lock(&xfrm4_protocol_mutex);
+
+	for (pprev = proto_handlers(protocol);
+	     (t = rcu_dereference_protected(*pprev,
+			lockdep_is_held(&xfrm4_protocol_mutex))) != NULL;
+	     pprev = &t->next) {
+		if (t == handler) {
+			*pprev = handler->next;
+			ret = 0;
+			break;
+		}
+	}
+
+	if (!rcu_dereference_protected(*proto_handlers(protocol),
+				       lockdep_is_held(&xfrm4_protocol_mutex))) {
+		if (inet_del_protocol(netproto(protocol), protocol) < 0) {
+			pr_err("%s: can't remove protocol\n", __func__);
+			ret = -EAGAIN;
+		}
+	}
+
+	mutex_unlock(&xfrm4_protocol_mutex);
+
+	synchronize_net();
+
+	return ret;
+}
+EXPORT_SYMBOL(xfrm4_protocol_deregister);
+
+void __init xfrm4_protocol_init(void)
+{
+	xfrm_input_register_afinfo(&xfrm4_input_afinfo);
+}