[PATCH v9 06/20] multi-process: define MPQemuMsg format and transmission functions

[elena.ufimtseva@oracle.com]

From: Elena Ufimtseva <elena.ufimtseva@oracle.com>

Defines MPQemuMsg, which is the message that is sent to the remote
process. This message is sent over QIOChannel and is used to
command the remote process to perform various tasks.

Also defined the helper functions to send and receive messages over the
QIOChannel

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
---
 MAINTAINERS              |   2 +
 include/io/mpqemu-link.h |  60 ++++++++++++++
 io/meson.build           |   2 +
 io/mpqemu-link.c         | 173 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 237 insertions(+)
 create mode 100644 include/io/mpqemu-link.h
 create mode 100644 io/mpqemu-link.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 38d19c83cd..1ca1f8ccff 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3045,6 +3045,8 @@ F: hw/pci-host/remote.c
 F: include/hw/pci-host/remote.h
 F: hw/i386/remote.c
 F: include/hw/i386/remote.h
+F: io/mpqemu-link.c
+F: include/io/mpqemu-link.h
 
 Build and test automation
 -------------------------
diff --git a/include/io/mpqemu-link.h b/include/io/mpqemu-link.h
new file mode 100644
index 0000000000..c7de8648bc
--- /dev/null
+++ b/include/io/mpqemu-link.h
@@ -0,0 +1,60 @@
+/*
+ * Communication channel between QEMU and remote device process
+ *
+ * Copyright © 2018, 2020 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#ifndef MPQEMU_LINK_H
+#define MPQEMU_LINK_H
+
+#include "qom/object.h"
+#include "qemu/thread.h"
+#include "io/channel.h"
+
+#define REMOTE_MAX_FDS 8
+
+#define MPQEMU_MSG_HDR_SIZE offsetof(MPQemuMsg, data.u64)
+
+/**
+ * MPQemuCmd:
+ *
+ * MPQemuCmd enum type to specify the command to be executed on the remote
+ * device.
+ */
+typedef enum {
+    INIT = 0,
+    MAX = INT_MAX,
+} MPQemuCmd;
+
+/**
+ * MPQemuMsg:
+ * @cmd: The remote command
+ * @size: Size of the data to be shared
+ * @data: Structured data
+ * @fds: File descriptors to be shared with remote device
+ *
+ * MPQemuMsg Format of the message sent to the remote device from QEMU.
+ *
+ */
+typedef struct {
+    int cmd;
+    size_t size;
+
+    union {
+        uint64_t u64;
+    } data;
+
+    int fds[REMOTE_MAX_FDS];
+    int num_fds;
+} MPQemuMsg;
+
+void mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp);
+void mpqemu_msg_recv(MPQemuMsg *msg, QIOChannel *ioc, Error **errp);
+
+bool mpqemu_msg_valid(MPQemuMsg *msg);
+
+#endif
diff --git a/io/meson.build b/io/meson.build
index 768c1b5ec3..3d40cd8867 100644
--- a/io/meson.build
+++ b/io/meson.build
@@ -15,6 +15,8 @@ io_ss.add(files(
   'task.c',
 ))
 
+io_ss.add(when: 'CONFIG_MPQEMU', if_true: files('mpqemu-link.c'))
+
 io_ss = io_ss.apply(config_host, strict: false)
 libio = static_library('io', io_ss.sources() + genh,
                        dependencies: [io_ss.dependencies()],
diff --git a/io/mpqemu-link.c b/io/mpqemu-link.c
new file mode 100644
index 0000000000..d9be2bdeab
--- /dev/null
+++ b/io/mpqemu-link.c
@@ -0,0 +1,173 @@
+/*
+ * Communication channel between QEMU and remote device process
+ *
+ * Copyright © 2018, 2020 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+
+#include "qemu/module.h"
+#include "io/mpqemu-link.h"
+#include "qapi/error.h"
+#include "qemu/iov.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+
+void mpqemu_msg_send(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
+{
+    bool iolock = qemu_mutex_iothread_locked();
+    Error *local_err = NULL;
+    struct iovec send[2];
+    int *fds = NULL;
+    size_t nfds = 0;
+
+    send[0].iov_base = msg;
+    send[0].iov_len = MPQEMU_MSG_HDR_SIZE;
+
+    send[1].iov_base = (void *)&msg->data;
+    send[1].iov_len = msg->size;
+
+    if (msg->num_fds) {
+        nfds = msg->num_fds;
+        fds = msg->fds;
+    }
+
+    if (iolock) {
+        qemu_mutex_unlock_iothread();
+    }
+
+    (void)qio_channel_writev_full_all(ioc, send, G_N_ELEMENTS(send), fds, nfds,
+                                      &local_err);
+
+    if (iolock) {
+        qemu_mutex_lock_iothread();
+    }
+
+    if (errp) {
+        error_propagate(errp, local_err);
+    } else if (local_err) {
+        error_report_err(local_err);
+    }
+
+    return;
+}
+
+static ssize_t mpqemu_read(QIOChannel *ioc, void *buf, size_t len, int **fds,
+                           size_t *nfds, Error **errp)
+{
+    struct iovec iov = { .iov_base = buf, .iov_len = len };
+    bool iolock = qemu_mutex_iothread_locked();
+    struct iovec *iovp = &iov;
+    Error *local_err = NULL;
+    unsigned int niov = 1;
+    size_t *l_nfds = nfds;
+    int **l_fds = fds;
+    ssize_t bytes = 0;
+    size_t size;
+
+    iov.iov_base = buf;
+    iov.iov_len = len;
+    size = iov.iov_len;
+
+    while (size > 0) {
+        bytes = qio_channel_readv_full(ioc, iovp, niov, l_fds, l_nfds,
+                                       &local_err);
+
+        if (bytes == QIO_CHANNEL_ERR_BLOCK) {
+            if (iolock) {
+                qemu_mutex_unlock_iothread();
+            }
+
+            if (qemu_in_coroutine()) {
+                qio_channel_yield(ioc, G_IO_IN);
+            } else {
+                qio_channel_wait(ioc, G_IO_IN);
+            }
+
+            if (iolock) {
+                qemu_mutex_lock_iothread();
+            }
+            continue;
+        }
+
+        if (bytes <= 0) {
+            error_propagate(errp, local_err);
+            return -EIO;
+        }
+
+        l_fds = NULL;
+        l_nfds = NULL;
+
+        size -= bytes;
+
+        (void)iov_discard_front(&iovp, &niov, bytes);
+    }
+
+    return len - size;
+}
+
+void mpqemu_msg_recv(MPQemuMsg *msg, QIOChannel *ioc, Error **errp)
+{
+    Error *local_err = NULL;
+    int *fds = NULL;
+    size_t nfds = 0;
+    ssize_t len;
+
+    len = mpqemu_read(ioc, (void *)msg, MPQEMU_MSG_HDR_SIZE, &fds, &nfds,
+                      &local_err);
+    if (len < 0) {
+        goto fail;
+    } else if (len != MPQEMU_MSG_HDR_SIZE) {
+        error_setg(&local_err, "Message header corrupted");
+        goto fail;
+    }
+
+    if (msg->size > sizeof(msg->data)) {
+        error_setg(&local_err, "Invalid size for message");
+        goto fail;
+    }
+
+    if (mpqemu_read(ioc, (void *)&msg->data, msg->size, NULL, NULL,
+                    &local_err) < 0) {
+        goto fail;
+    }
+
+    msg->num_fds = nfds;
+    if (nfds) {
+        memcpy(msg->fds, fds, nfds * sizeof(int));
+    }
+
+fail:
+    if (errp) {
+        error_propagate(errp, local_err);
+    } else if (local_err) {
+        error_report_err(local_err);
+    }
+}
+
+bool mpqemu_msg_valid(MPQemuMsg *msg)
+{
+    if (msg->cmd >= MAX && msg->cmd < 0) {
+        return false;
+    }
+
+    /* Verify FDs. */
+    if (msg->num_fds >= REMOTE_MAX_FDS) {
+        return false;
+    }
+
+    if (msg->num_fds > 0) {
+        for (int i = 0; i < msg->num_fds; i++) {
+            if (fcntl(msg->fds[i], F_GETFL) == -1) {
+                return false;
+            }
+        }
+    }
+
+    return true;
+}
-- 
2.25.GIT