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, 192 insertions, 0 deletions

diff --git a/io_uring/cmd_net.c b/io_uring/cmd_net.c
new file mode 100644
index 000000000..7cd411fc4
--- /dev/null
+++ b/io_uring/cmd_net.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <asm/ioctls.h>
+#include <linux/io_uring/net.h>
+#include <linux/errqueue.h>
+#include <net/sock.h>
+
+#include "uring_cmd.h"
+#include "io_uring.h"
+
+static int io_uring_cmd_get_sock_ioctl(struct socket *sock, int op)
+{
+	struct sock *sk = sock->sk;
+	struct proto *prot = READ_ONCE(sk->sk_prot);
+	int ret, arg = 0;
+
+	if (!prot || !prot->ioctl)
+		return -EOPNOTSUPP;
+
+	ret = prot->ioctl(sk, op, &arg);
+	if (ret)
+		return ret;
+	return arg;
+}
+
+static inline int io_uring_cmd_getsockopt(struct socket *sock,
+					  struct io_uring_cmd *cmd,
+					  unsigned int issue_flags)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	bool compat = !!(issue_flags & IO_URING_F_COMPAT);
+	int optlen, optname, level, err;
+	void __user *optval;
+
+	level = READ_ONCE(sqe->level);
+	if (level != SOL_SOCKET)
+		return -EOPNOTSUPP;
+
+	optval = u64_to_user_ptr(READ_ONCE(sqe->optval));
+	optname = READ_ONCE(sqe->optname);
+	optlen = READ_ONCE(sqe->optlen);
+
+	err = do_sock_getsockopt(sock, compat, level, optname,
+				 USER_SOCKPTR(optval),
+				 KERNEL_SOCKPTR(&optlen));
+	if (err)
+		return err;
+
+	/* On success, return optlen */
+	return optlen;
+}
+
+static inline int io_uring_cmd_setsockopt(struct socket *sock,
+					  struct io_uring_cmd *cmd,
+					  unsigned int issue_flags)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	bool compat = !!(issue_flags & IO_URING_F_COMPAT);
+	int optname, optlen, level;
+	void __user *optval;
+	sockptr_t optval_s;
+
+	optval = u64_to_user_ptr(READ_ONCE(sqe->optval));
+	optname = READ_ONCE(sqe->optname);
+	optlen = READ_ONCE(sqe->optlen);
+	level = READ_ONCE(sqe->level);
+	optval_s = USER_SOCKPTR(optval);
+
+	return do_sock_setsockopt(sock, compat, level, optname, optval_s,
+				  optlen);
+}
+
+static bool io_process_timestamp_skb(struct io_uring_cmd *cmd, struct sock *sk,
+				     struct sk_buff *skb, unsigned issue_flags)
+{
+	struct sock_exterr_skb *serr = SKB_EXT_ERR(skb);
+	struct io_uring_cqe cqe[2];
+	struct io_timespec *iots;
+	struct timespec64 ts;
+	u32 tstype, tskey;
+	int ret;
+
+	BUILD_BUG_ON(sizeof(struct io_uring_cqe) != sizeof(struct io_timespec));
+
+	ret = skb_get_tx_timestamp(skb, sk, &ts);
+	if (ret < 0)
+		return false;
+
+	tskey = serr->ee.ee_data;
+	tstype = serr->ee.ee_info;
+
+	cqe->user_data = 0;
+	cqe->res = tskey;
+	cqe->flags = IORING_CQE_F_MORE | ctx_cqe32_flags(cmd_to_io_kiocb(cmd)->ctx);
+	cqe->flags |= tstype << IORING_TIMESTAMP_TYPE_SHIFT;
+	if (ret == SOF_TIMESTAMPING_TX_HARDWARE)
+		cqe->flags |= IORING_CQE_F_TSTAMP_HW;
+
+	iots = (struct io_timespec *)&cqe[1];
+	iots->tv_sec = ts.tv_sec;
+	iots->tv_nsec = ts.tv_nsec;
+	return io_uring_cmd_post_mshot_cqe32(cmd, issue_flags, cqe);
+}
+
+static int io_uring_cmd_timestamp(struct socket *sock,
+				  struct io_uring_cmd *cmd,
+				  unsigned int issue_flags)
+{
+	struct sock *sk = sock->sk;
+	struct sk_buff_head *q = &sk->sk_error_queue;
+	struct sk_buff *skb, *tmp;
+	struct sk_buff_head list;
+	int ret;
+
+	if (!(issue_flags & IO_URING_F_CQE32))
+		return -EINVAL;
+	ret = io_cmd_poll_multishot(cmd, issue_flags, EPOLLERR);
+	if (unlikely(ret))
+		return ret;
+
+	if (skb_queue_empty_lockless(q))
+		return -EAGAIN;
+	__skb_queue_head_init(&list);
+
+	scoped_guard(spinlock_irq, &q->lock) {
+		skb_queue_walk_safe(q, skb, tmp) {
+			/* don't support skbs with payload */
+			if (!skb_has_tx_timestamp(skb, sk) || skb->len)
+				continue;
+			__skb_unlink(skb, q);
+			__skb_queue_tail(&list, skb);
+		}
+	}
+
+	while (1) {
+		skb = skb_peek(&list);
+		if (!skb)
+			break;
+		if (!io_process_timestamp_skb(cmd, sk, skb, issue_flags))
+			break;
+		__skb_dequeue(&list);
+		consume_skb(skb);
+	}
+
+	if (!unlikely(skb_queue_empty(&list))) {
+		scoped_guard(spinlock_irqsave, &q->lock)
+			skb_queue_splice(&list, q);
+	}
+	return -EAGAIN;
+}
+
+static int io_uring_cmd_getsockname(struct socket *sock,
+				    struct io_uring_cmd *cmd,
+				    unsigned int issue_flags)
+{
+	const struct io_uring_sqe *sqe = cmd->sqe;
+	struct sockaddr __user *uaddr;
+	unsigned int peer;
+	int __user *ulen;
+
+	if (sqe->ioprio || sqe->__pad1 || sqe->len || sqe->rw_flags)
+		return -EINVAL;
+
+	uaddr = u64_to_user_ptr(READ_ONCE(sqe->addr));
+	ulen = u64_to_user_ptr(READ_ONCE(sqe->addr3));
+	peer = READ_ONCE(sqe->optlen);
+	if (peer > 1)
+		return -EINVAL;
+	return do_getsockname(sock, peer, uaddr, ulen);
+}
+
+int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags)
+{
+	struct socket *sock = cmd->file->private_data;
+
+	switch (cmd->cmd_op) {
+	case SOCKET_URING_OP_SIOCINQ:
+		return io_uring_cmd_get_sock_ioctl(sock, SIOCINQ);
+	case SOCKET_URING_OP_SIOCOUTQ:
+		return io_uring_cmd_get_sock_ioctl(sock, SIOCOUTQ);
+	case SOCKET_URING_OP_GETSOCKOPT:
+		return io_uring_cmd_getsockopt(sock, cmd, issue_flags);
+	case SOCKET_URING_OP_SETSOCKOPT:
+		return io_uring_cmd_setsockopt(sock, cmd, issue_flags);
+	case SOCKET_URING_OP_TX_TIMESTAMP:
+		return io_uring_cmd_timestamp(sock, cmd, issue_flags);
+	case SOCKET_URING_OP_GETSOCKNAME:
+		return io_uring_cmd_getsockname(sock, cmd, issue_flags);
+	default:
+		return -EOPNOTSUPP;
+	}
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_sock);