[Qemu-devel] [PULL 16/57] Return path: Open a return path on QEMUFile for sockets

[Juan Quintela]

From: "Dr. David Alan Gilbert" 

Postcopy needs a method to send messages from the destination back to
the source, this is the 'return path'.

Wire it up for 'socket' QEMUFile's.

Signed-off-by: Dr. David Alan Gilbert 
Reviewed-by: Juan Quintela 
Reviewed-by: Amit Shah 
Signed-off-by: Juan Quintela 
---
 include/migration/qemu-file.h |  7 +
 migration/qemu-file-unix.c| 69 +--
 migration/qemu-file.c | 12 
 3 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 66e741f..b5d08d2 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -89,6 +89,11 @@ typedef size_t (QEMURamSaveFunc)(QEMUFile *f, void *opaque,
uint64_t *bytes_sent);

 /*
+ * Return a QEMUFile for comms in the opposite direction
+ */
+typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
+
+/*
  * Stop any read or write (depending on flags) on the underlying
  * transport on the QEMUFile.
  * Existing blocking reads/writes must be woken
@@ -106,6 +111,7 @@ typedef struct QEMUFileOps {
 QEMURamHookFunc *after_ram_iterate;
 QEMURamHookFunc *hook_ram_load;
 QEMURamSaveFunc *save_page;
+QEMURetPathFunc *get_return_path;
 QEMUFileShutdownFunc *shut_down;
 } QEMUFileOps;

@@ -196,6 +202,7 @@ int64_t qemu_file_get_rate_limit(QEMUFile *f);
 int qemu_file_get_error(QEMUFile *f);
 void qemu_file_set_error(QEMUFile *f, int ret);
 int qemu_file_shutdown(QEMUFile *f);
+QEMUFile *qemu_file_get_return_path(QEMUFile *f);
 void qemu_fflush(QEMUFile *f);
 void qemu_file_set_blocking(QEMUFile *f, bool block);

diff --git a/migration/qemu-file-unix.c b/migration/qemu-file-unix.c
index 809bf07..bcb744b 100644
--- a/migration/qemu-file-unix.c
+++ b/migration/qemu-file-unix.c
@@ -97,6 +97,56 @@ static int socket_shutdown(void *opaque, bool rd, bool wr)
 }
 }

+static int socket_return_close(void *opaque)
+{
+QEMUFileSocket *s = opaque;
+/*
+ * Note: We don't close the socket, that should be done by the forward
+ * path.
+ */
+g_free(s);
+return 0;
+}
+
+static const QEMUFileOps socket_return_read_ops = {
+.get_fd  = socket_get_fd,
+.get_buffer  = socket_get_buffer,
+.close   = socket_return_close,
+.shut_down   = socket_shutdown,
+};
+
+static const QEMUFileOps socket_return_write_ops = {
+.get_fd  = socket_get_fd,
+.writev_buffer   = socket_writev_buffer,
+.close   = socket_return_close,
+.shut_down   = socket_shutdown,
+};
+
+/*
+ * Give a QEMUFile* off the same socket but data in the opposite
+ * direction.
+ */
+static QEMUFile *socket_get_return_path(void *opaque)
+{
+QEMUFileSocket *forward = opaque;
+QEMUFileSocket *reverse;
+
+if (qemu_file_get_error(forward->file)) {
+/* If the forward file is in error, don't try and open a return */
+return NULL;
+}
+
+reverse = g_malloc0(sizeof(QEMUFileSocket));
+reverse->fd = forward->fd;
+/* I don't think there's a better way to tell which direction 'this' is */
+if (forward->file->ops->get_buffer != NULL) {
+/* being called from the read side, so we need to be able to write */
+return qemu_fopen_ops(reverse, _return_write_ops);
+} else {
+return qemu_fopen_ops(reverse, _return_read_ops);
+}
+}
+
 static ssize_t unix_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
   int64_t pos)
 {
@@ -206,18 +256,19 @@ QEMUFile *qemu_fdopen(int fd, const char *mode)
 }

 static const QEMUFileOps socket_read_ops = {
-.get_fd = socket_get_fd,
-.get_buffer = socket_get_buffer,
-.close  = socket_close,
-.shut_down  = socket_shutdown
-
+.get_fd  = socket_get_fd,
+.get_buffer  = socket_get_buffer,
+.close   = socket_close,
+.shut_down   = socket_shutdown,
+.get_return_path = socket_get_return_path
 };

 static const QEMUFileOps socket_write_ops = {
-.get_fd= socket_get_fd,
-.writev_buffer = socket_writev_buffer,
-.close = socket_close,
-.shut_down = socket_shutdown
+.get_fd  = socket_get_fd,
+.writev_buffer   = socket_writev_buffer,
+.close   = socket_close,
+.shut_down   = socket_shutdown,
+.get_return_path = socket_get_return_path
 };

 QEMUFile *qemu_fopen_socket(int fd, const char *mode)
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 9ec2267..0bbd257 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -44,6 +44,18 @@ int qemu_file_shutdown(QEMUFile *f)
 return f->ops->shut_down(f->opaque, true, true);
 }

+/*
+ * Result: QEMUFile* for a 'return path' for comms in the opposite direction
+ * NULL if not available

[Qemu-devel] [PULL 16/57] Return path: Open a return path on QEMUFile for sockets

[Juan Quintela]

From: "Dr. David Alan Gilbert" 

Postcopy needs a method to send messages from the destination back to
the source, this is the 'return path'.

Wire it up for 'socket' QEMUFile's.

Signed-off-by: Dr. David Alan Gilbert 
Reviewed-by: Juan Quintela 
Reviewed-by: Amit Shah 
Signed-off-by: Juan Quintela 
---
 include/migration/qemu-file.h |  7 +
 migration/qemu-file-unix.c| 69 +--
 migration/qemu-file.c | 12 
 3 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
index 66e741f..b5d08d2 100644
--- a/include/migration/qemu-file.h
+++ b/include/migration/qemu-file.h
@@ -89,6 +89,11 @@ typedef size_t (QEMURamSaveFunc)(QEMUFile *f, void *opaque,
uint64_t *bytes_sent);

 /*
+ * Return a QEMUFile for comms in the opposite direction
+ */
+typedef QEMUFile *(QEMURetPathFunc)(void *opaque);
+
+/*
  * Stop any read or write (depending on flags) on the underlying
  * transport on the QEMUFile.
  * Existing blocking reads/writes must be woken
@@ -106,6 +111,7 @@ typedef struct QEMUFileOps {
 QEMURamHookFunc *after_ram_iterate;
 QEMURamHookFunc *hook_ram_load;
 QEMURamSaveFunc *save_page;
+QEMURetPathFunc *get_return_path;
 QEMUFileShutdownFunc *shut_down;
 } QEMUFileOps;

@@ -196,6 +202,7 @@ int64_t qemu_file_get_rate_limit(QEMUFile *f);
 int qemu_file_get_error(QEMUFile *f);
 void qemu_file_set_error(QEMUFile *f, int ret);
 int qemu_file_shutdown(QEMUFile *f);
+QEMUFile *qemu_file_get_return_path(QEMUFile *f);
 void qemu_fflush(QEMUFile *f);
 void qemu_file_set_blocking(QEMUFile *f, bool block);

diff --git a/migration/qemu-file-unix.c b/migration/qemu-file-unix.c
index 809bf07..bcb744b 100644
--- a/migration/qemu-file-unix.c
+++ b/migration/qemu-file-unix.c
@@ -97,6 +97,56 @@ static int socket_shutdown(void *opaque, bool rd, bool wr)
 }
 }

+static int socket_return_close(void *opaque)
+{
+QEMUFileSocket *s = opaque;
+/*
+ * Note: We don't close the socket, that should be done by the forward
+ * path.
+ */
+g_free(s);
+return 0;
+}
+
+static const QEMUFileOps socket_return_read_ops = {
+.get_fd  = socket_get_fd,
+.get_buffer  = socket_get_buffer,
+.close   = socket_return_close,
+.shut_down   = socket_shutdown,
+};
+
+static const QEMUFileOps socket_return_write_ops = {
+.get_fd  = socket_get_fd,
+.writev_buffer   = socket_writev_buffer,
+.close   = socket_return_close,
+.shut_down   = socket_shutdown,
+};
+
+/*
+ * Give a QEMUFile* off the same socket but data in the opposite
+ * direction.
+ */
+static QEMUFile *socket_get_return_path(void *opaque)
+{
+QEMUFileSocket *forward = opaque;
+QEMUFileSocket *reverse;
+
+if (qemu_file_get_error(forward->file)) {
+/* If the forward file is in error, don't try and open a return */
+return NULL;
+}
+
+reverse = g_malloc0(sizeof(QEMUFileSocket));
+reverse->fd = forward->fd;
+/* I don't think there's a better way to tell which direction 'this' is */
+if (forward->file->ops->get_buffer != NULL) {
+/* being called from the read side, so we need to be able to write */
+return qemu_fopen_ops(reverse, _return_write_ops);
+} else {
+return qemu_fopen_ops(reverse, _return_read_ops);
+}
+}
+
 static ssize_t unix_writev_buffer(void *opaque, struct iovec *iov, int iovcnt,
   int64_t pos)
 {
@@ -206,18 +256,19 @@ QEMUFile *qemu_fdopen(int fd, const char *mode)
 }

 static const QEMUFileOps socket_read_ops = {
-.get_fd = socket_get_fd,
-.get_buffer = socket_get_buffer,
-.close  = socket_close,
-.shut_down  = socket_shutdown
-
+.get_fd  = socket_get_fd,
+.get_buffer  = socket_get_buffer,
+.close   = socket_close,
+.shut_down   = socket_shutdown,
+.get_return_path = socket_get_return_path
 };

 static const QEMUFileOps socket_write_ops = {
-.get_fd= socket_get_fd,
-.writev_buffer = socket_writev_buffer,
-.close = socket_close,
-.shut_down = socket_shutdown
+.get_fd  = socket_get_fd,
+.writev_buffer   = socket_writev_buffer,
+.close   = socket_close,
+.shut_down   = socket_shutdown,
+.get_return_path = socket_get_return_path
 };

 QEMUFile *qemu_fopen_socket(int fd, const char *mode)
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 9ec2267..0bbd257 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -44,6 +44,18 @@ int qemu_file_shutdown(QEMUFile *f)
 return f->ops->shut_down(f->opaque, true, true);
 }

+/*
+ * Result: QEMUFile* for a 'return path' for comms in the opposite direction
+ * NULL if not available