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, 50 insertions, 0 deletions

diff --git a/include/net/tun_proto.h b/include/net/tun_proto.h
new file mode 100644
index 000000000..7b0de7852
--- /dev/null
+++ b/include/net/tun_proto.h
@@ -0,0 +1,50 @@
+#ifndef __NET_TUN_PROTO_H
+#define __NET_TUN_PROTO_H
+
+#include <linux/if_ether.h>
+#include <linux/types.h>
+
+/* One byte protocol values as defined by VXLAN-GPE and NSH. These will
+ * hopefully get a shared IANA registry.
+ */
+#define TUN_P_IPV4      0x01
+#define TUN_P_IPV6      0x02
+#define TUN_P_ETHERNET  0x03
+#define TUN_P_NSH       0x04
+#define TUN_P_MPLS_UC   0x05
+
+static inline __be16 tun_p_to_eth_p(u8 proto)
+{
+	switch (proto) {
+	case TUN_P_IPV4:
+		return htons(ETH_P_IP);
+	case TUN_P_IPV6:
+		return htons(ETH_P_IPV6);
+	case TUN_P_ETHERNET:
+		return htons(ETH_P_TEB);
+	case TUN_P_NSH:
+		return htons(ETH_P_NSH);
+	case TUN_P_MPLS_UC:
+		return htons(ETH_P_MPLS_UC);
+	}
+	return 0;
+}
+
+static inline u8 tun_p_from_eth_p(__be16 proto)
+{
+	switch (proto) {
+	case htons(ETH_P_IP):
+		return TUN_P_IPV4;
+	case htons(ETH_P_IPV6):
+		return TUN_P_IPV6;
+	case htons(ETH_P_TEB):
+		return TUN_P_ETHERNET;
+	case htons(ETH_P_NSH):
+		return TUN_P_NSH;
+	case htons(ETH_P_MPLS_UC):
+		return TUN_P_MPLS_UC;
+	}
+	return 0;
+}
+
+#endif