Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 93 insertions, 0 deletions

diff --git a/util/qemu-coroutine-io.c b/util/qemu-coroutine-io.c
new file mode 100644
index 000000000..5b80bb416
--- /dev/null
+++ b/util/qemu-coroutine-io.c
@@ -0,0 +1,93 @@
+/*
+ * Coroutine-aware I/O functions
+ *
+ * Copyright (C) 2009-2010 Nippon Telegraph and Telephone Corporation.
+ * Copyright (c) 2011, Red Hat, Inc.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "qemu/sockets.h"
+#include "qemu/coroutine.h"
+#include "qemu/iov.h"
+#include "qemu/main-loop.h"
+
+ssize_t coroutine_fn
+qemu_co_sendv_recvv(int sockfd, struct iovec *iov, unsigned iov_cnt,
+                    size_t offset, size_t bytes, bool do_send)
+{
+    size_t done = 0;
+    ssize_t ret;
+    while (done < bytes) {
+        ret = iov_send_recv(sockfd, iov, iov_cnt,
+                            offset + done, bytes - done, do_send);
+        if (ret > 0) {
+            done += ret;
+        } else if (ret < 0) {
+            if (errno == EAGAIN || errno == EWOULDBLOCK) {
+                qemu_coroutine_yield();
+            } else if (done == 0) {
+                return -errno;
+            } else {
+                break;
+            }
+        } else if (ret == 0 && !do_send) {
+            /* write (send) should never return 0.
+             * read (recv) returns 0 for end-of-file (-data).
+             * In both cases there's little point retrying,
+             * but we do for write anyway, just in case */
+            break;
+        }
+    }
+    return done;
+}
+
+ssize_t coroutine_fn
+qemu_co_send_recv(int sockfd, void *buf, size_t bytes, bool do_send)
+{
+    struct iovec iov = { .iov_base = buf, .iov_len = bytes };
+    return qemu_co_sendv_recvv(sockfd, &iov, 1, 0, bytes, do_send);
+}
+
+typedef struct {
+    AioContext *ctx;
+    Coroutine *co;
+    int fd;
+} FDYieldUntilData;
+
+static void fd_coroutine_enter(void *opaque)
+{
+    FDYieldUntilData *data = opaque;
+    aio_set_fd_handler(data->ctx, data->fd, false, NULL, NULL, NULL, NULL);
+    qemu_coroutine_enter(data->co);
+}
+
+void coroutine_fn yield_until_fd_readable(int fd)
+{
+    FDYieldUntilData data;
+
+    assert(qemu_in_coroutine());
+    data.ctx = qemu_get_current_aio_context();
+    data.co = qemu_coroutine_self();
+    data.fd = fd;
+    aio_set_fd_handler(
+        data.ctx, fd, false, fd_coroutine_enter, NULL, NULL, &data);
+    qemu_coroutine_yield();
+}