[PATCH V3 0/2] migration file URI

[PATCH V3 0/2] migration file URI

[Steve Sistare]

Add the migration URI "file:filename[,offset=offset]".

Fabiano Rosas has also written preliminary patches for the file uri, and
he will submit the unit test(s).

Steve Sistare (2):
  migration: file URI
  migration: file URI offset

 migration/file.c       | 103 +++++++++++++++++++++++++++++++++++++++++++++++++
 migration/file.h       |  14 +++++++
 migration/meson.build  |   1 +
 migration/migration.c  |   5 +++
 migration/trace-events |   4 ++
 qemu-options.hx        |   7 +++-
 6 files changed, 133 insertions(+), 1 deletion(-)
 create mode 100644 migration/file.c
 create mode 100644 migration/file.h

-- 
1.8.3.1

[PATCH V3 1/2] migration: file URI

[Steve Sistare]

Extend the migration URI to support file:<filename>.  This can be used for
any migration scenario that does not require a reverse path.  It can be
used as an alternative to 'exec:cat > file' in minimized containers that
do not contain /bin/sh, and it is easier to use than the fd:<fdname> URI.
It can be used in HMP commands, and as a qemu command-line parameter.

For best performance, guest ram should be shared and x-ignore-shared
should be true, so guest pages are not written to the file, in which case
the guest may remain running.  If ram is not so configured, then the user
is advised to stop the guest first.  Otherwise, a busy guest may re-dirty
the same page, causing it to be appended to the file multiple times,
and the file may grow unboundedly.  That issue is being addressed in the
"fixed-ram" patch series.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Fabiano Rosas <farosas@suse.de>
---
 migration/file.c       | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
 migration/file.h       | 14 ++++++++++++
 migration/meson.build  |  1 +
 migration/migration.c  |  5 ++++
 migration/trace-events |  4 ++++
 qemu-options.hx        |  6 ++++-
 6 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 migration/file.c
 create mode 100644 migration/file.h

diff --git a/migration/file.c b/migration/file.c
new file mode 100644
index 0000000..8e35827
--- /dev/null
+++ b/migration/file.c
@@ -0,0 +1,62 @@
+/*
+ * Copyright (c) 2021-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "channel.h"
+#include "file.h"
+#include "migration.h"
+#include "io/channel-file.h"
+#include "io/channel-util.h"
+#include "trace.h"
+
+void file_start_outgoing_migration(MigrationState *s, const char *filename,
+                                   Error **errp)
+{
+    g_autoptr(QIOChannelFile) fioc = NULL;
+    QIOChannel *ioc;
+
+    trace_migration_file_outgoing(filename);
+
+    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
+                                     0600, errp);
+    if (!fioc) {
+        return;
+    }
+
+    ioc = QIO_CHANNEL(fioc);
+    qio_channel_set_name(ioc, "migration-file-outgoing");
+    migration_channel_connect(s, ioc, NULL, NULL);
+}
+
+static gboolean file_accept_incoming_migration(QIOChannel *ioc,
+                                               GIOCondition condition,
+                                               gpointer opaque)
+{
+    migration_channel_process_incoming(ioc);
+    object_unref(OBJECT(ioc));
+    return G_SOURCE_REMOVE;
+}
+
+void file_start_incoming_migration(const char *filename, Error **errp)
+{
+    QIOChannelFile *fioc = NULL;
+    QIOChannel *ioc;
+
+    trace_migration_file_incoming(filename);
+
+    fioc = qio_channel_file_new_path(filename, O_RDONLY, 0, errp);
+    if (!fioc) {
+        return;
+    }
+
+    ioc = QIO_CHANNEL(fioc);
+    qio_channel_set_name(QIO_CHANNEL(ioc), "migration-file-incoming");
+    qio_channel_add_watch_full(ioc, G_IO_IN,
+                               file_accept_incoming_migration,
+                               NULL, NULL,
+                               g_main_context_get_thread_default());
+}
diff --git a/migration/file.h b/migration/file.h
new file mode 100644
index 0000000..841b94a
--- /dev/null
+++ b/migration/file.h
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2021-2023 Oracle and/or its affiliates.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef QEMU_MIGRATION_FILE_H
+#define QEMU_MIGRATION_FILE_H
+void file_start_incoming_migration(const char *filename, Error **errp);
+
+void file_start_outgoing_migration(MigrationState *s, const char *filename,
+                                   Error **errp);
+#endif
diff --git a/migration/meson.build b/migration/meson.build
index 8ba6e42..3af817e 100644
--- a/migration/meson.build
+++ b/migration/meson.build
@@ -16,6 +16,7 @@ softmmu_ss.add(files(
   'dirtyrate.c',
   'exec.c',
   'fd.c',
+  'file.c',
   'global_state.c',
   'migration-hmp-cmds.c',
   'migration.c',
diff --git a/migration/migration.c b/migration/migration.c
index dc05c6f..cfbde86 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -20,6 +20,7 @@
 #include "migration/blocker.h"
 #include "exec.h"
 #include "fd.h"
+#include "file.h"
 #include "socket.h"
 #include "sysemu/runstate.h"
 #include "sysemu/sysemu.h"
@@ -442,6 +443,8 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
         exec_start_incoming_migration(p, errp);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_incoming_migration(p, errp);
+    } else if (strstart(uri, "file:", &p)) {
+        file_start_incoming_migration(p, errp);
     } else {
         error_setg(errp, "unknown migration protocol: %s", uri);
     }
@@ -1662,6 +1665,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
         exec_start_outgoing_migration(s, p, &local_err);
     } else if (strstart(uri, "fd:", &p)) {
         fd_start_outgoing_migration(s, p, &local_err);
+    } else if (strstart(uri, "file:", &p)) {
+        file_start_outgoing_migration(s, p, &local_err);
     } else {
         if (!(has_resume && resume)) {
             yank_unregister_instance(MIGRATION_YANK_INSTANCE);
diff --git a/migration/trace-events b/migration/trace-events
index cdaef7a..c8c1771 100644
--- a/migration/trace-events
+++ b/migration/trace-events
@@ -307,6 +307,10 @@ migration_exec_incoming(const char *cmd) "cmd=%s"
 migration_fd_outgoing(int fd) "fd=%d"
 migration_fd_incoming(int fd) "fd=%d"
 
+# file.c
+migration_file_outgoing(const char *filename) "filename=%s"
+migration_file_incoming(const char *filename) "filename=%s"
+
 # socket.c
 migration_socket_incoming_accepted(void) ""
 migration_socket_outgoing_connected(const char *hostname) "hostname=%s"
diff --git a/qemu-options.hx b/qemu-options.hx
index b57489d..5aab8fb 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4622,6 +4622,7 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
     "                prepare for incoming migration, listen on\n" \
     "                specified protocol and socket address\n" \
     "-incoming fd:fd\n" \
+    "-incoming file:filename\n" \
     "-incoming exec:cmdline\n" \
     "                accept incoming migration on given file descriptor\n" \
     "                or from given external command\n" \
@@ -4638,7 +4639,10 @@ SRST
     Prepare for incoming migration, listen on a given unix socket.
 
 ``-incoming fd:fd``
-    Accept incoming migration from a given filedescriptor.
+    Accept incoming migration from a given file descriptor.
+
+``-incoming file:filename``
+    Accept incoming migration from a given file.
 
 ``-incoming exec:cmdline``
     Accept incoming migration as an output from specified external
-- 
1.8.3.1

Re: [PATCH V3 1/2] migration: file URI

[Peter Xu]

On Thu, Jun 22, 2023 at 01:37:30PM -0700, Steve Sistare wrote:
> Extend the migration URI to support file:<filename>.  This can be used for
> any migration scenario that does not require a reverse path.  It can be
> used as an alternative to 'exec:cat > file' in minimized containers that
> do not contain /bin/sh, and it is easier to use than the fd:<fdname> URI.
> It can be used in HMP commands, and as a qemu command-line parameter.
> 
> For best performance, guest ram should be shared and x-ignore-shared
> should be true, so guest pages are not written to the file, in which case
> the guest may remain running.  If ram is not so configured, then the user
> is advised to stop the guest first.  Otherwise, a busy guest may re-dirty
> the same page, causing it to be appended to the file multiple times,
> and the file may grow unboundedly.  That issue is being addressed in the
> "fixed-ram" patch series.
> 
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> Reviewed-by: Fabiano Rosas <farosas@suse.de>
> ---
>  migration/file.c       | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  migration/file.h       | 14 ++++++++++++
>  migration/meson.build  |  1 +
>  migration/migration.c  |  5 ++++
>  migration/trace-events |  4 ++++
>  qemu-options.hx        |  6 ++++-
>  6 files changed, 91 insertions(+), 1 deletion(-)
>  create mode 100644 migration/file.c
>  create mode 100644 migration/file.h
> 
> diff --git a/migration/file.c b/migration/file.c
> new file mode 100644
> index 0000000..8e35827
> --- /dev/null
> +++ b/migration/file.c
> @@ -0,0 +1,62 @@
> +/*
> + * Copyright (c) 2021-2023 Oracle and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "channel.h"
> +#include "file.h"
> +#include "migration.h"
> +#include "io/channel-file.h"
> +#include "io/channel-util.h"
> +#include "trace.h"
> +
> +void file_start_outgoing_migration(MigrationState *s, const char *filename,
> +                                   Error **errp)
> +{
> +    g_autoptr(QIOChannelFile) fioc = NULL;
> +    QIOChannel *ioc;
> +
> +    trace_migration_file_outgoing(filename);
> +
> +    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
> +                                     0600, errp);
> +    if (!fioc) {
> +        return;
> +    }
> +
> +    ioc = QIO_CHANNEL(fioc);
> +    qio_channel_set_name(ioc, "migration-file-outgoing");
> +    migration_channel_connect(s, ioc, NULL, NULL);

Miss one object_unref(ioc)?

> +}
> +
> +static gboolean file_accept_incoming_migration(QIOChannel *ioc,
> +                                               GIOCondition condition,
> +                                               gpointer opaque)
> +{
> +    migration_channel_process_incoming(ioc);
> +    object_unref(OBJECT(ioc));
> +    return G_SOURCE_REMOVE;
> +}
> +
> +void file_start_incoming_migration(const char *filename, Error **errp)
> +{
> +    QIOChannelFile *fioc = NULL;
> +    QIOChannel *ioc;
> +
> +    trace_migration_file_incoming(filename);
> +
> +    fioc = qio_channel_file_new_path(filename, O_RDONLY, 0, errp);
> +    if (!fioc) {
> +        return;
> +    }
> +
> +    ioc = QIO_CHANNEL(fioc);
> +    qio_channel_set_name(QIO_CHANNEL(ioc), "migration-file-incoming");
> +    qio_channel_add_watch_full(ioc, G_IO_IN,
> +                               file_accept_incoming_migration,
> +                               NULL, NULL,
> +                               g_main_context_get_thread_default());
> +}
> diff --git a/migration/file.h b/migration/file.h
> new file mode 100644
> index 0000000..841b94a
> --- /dev/null
> +++ b/migration/file.h
> @@ -0,0 +1,14 @@
> +/*
> + * Copyright (c) 2021-2023 Oracle and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef QEMU_MIGRATION_FILE_H
> +#define QEMU_MIGRATION_FILE_H
> +void file_start_incoming_migration(const char *filename, Error **errp);
> +
> +void file_start_outgoing_migration(MigrationState *s, const char *filename,
> +                                   Error **errp);
> +#endif
> diff --git a/migration/meson.build b/migration/meson.build
> index 8ba6e42..3af817e 100644
> --- a/migration/meson.build
> +++ b/migration/meson.build
> @@ -16,6 +16,7 @@ softmmu_ss.add(files(
>    'dirtyrate.c',
>    'exec.c',
>    'fd.c',
> +  'file.c',
>    'global_state.c',
>    'migration-hmp-cmds.c',
>    'migration.c',
> diff --git a/migration/migration.c b/migration/migration.c
> index dc05c6f..cfbde86 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -20,6 +20,7 @@
>  #include "migration/blocker.h"
>  #include "exec.h"
>  #include "fd.h"
> +#include "file.h"
>  #include "socket.h"
>  #include "sysemu/runstate.h"
>  #include "sysemu/sysemu.h"
> @@ -442,6 +443,8 @@ static void qemu_start_incoming_migration(const char *uri, Error **errp)
>          exec_start_incoming_migration(p, errp);
>      } else if (strstart(uri, "fd:", &p)) {
>          fd_start_incoming_migration(p, errp);
> +    } else if (strstart(uri, "file:", &p)) {
> +        file_start_incoming_migration(p, errp);
>      } else {
>          error_setg(errp, "unknown migration protocol: %s", uri);
>      }
> @@ -1662,6 +1665,8 @@ void qmp_migrate(const char *uri, bool has_blk, bool blk,
>          exec_start_outgoing_migration(s, p, &local_err);
>      } else if (strstart(uri, "fd:", &p)) {
>          fd_start_outgoing_migration(s, p, &local_err);
> +    } else if (strstart(uri, "file:", &p)) {
> +        file_start_outgoing_migration(s, p, &local_err);
>      } else {
>          if (!(has_resume && resume)) {
>              yank_unregister_instance(MIGRATION_YANK_INSTANCE);
> diff --git a/migration/trace-events b/migration/trace-events
> index cdaef7a..c8c1771 100644
> --- a/migration/trace-events
> +++ b/migration/trace-events
> @@ -307,6 +307,10 @@ migration_exec_incoming(const char *cmd) "cmd=%s"
>  migration_fd_outgoing(int fd) "fd=%d"
>  migration_fd_incoming(int fd) "fd=%d"
>  
> +# file.c
> +migration_file_outgoing(const char *filename) "filename=%s"
> +migration_file_incoming(const char *filename) "filename=%s"
> +
>  # socket.c
>  migration_socket_incoming_accepted(void) ""
>  migration_socket_outgoing_connected(const char *hostname) "hostname=%s"
> diff --git a/qemu-options.hx b/qemu-options.hx
> index b57489d..5aab8fb 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -4622,6 +4622,7 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
>      "                prepare for incoming migration, listen on\n" \
>      "                specified protocol and socket address\n" \
>      "-incoming fd:fd\n" \
> +    "-incoming file:filename\n" \
>      "-incoming exec:cmdline\n" \
>      "                accept incoming migration on given file descriptor\n" \
>      "                or from given external command\n" \
> @@ -4638,7 +4639,10 @@ SRST
>      Prepare for incoming migration, listen on a given unix socket.
>  
>  ``-incoming fd:fd``
> -    Accept incoming migration from a given filedescriptor.
> +    Accept incoming migration from a given file descriptor.
> +
> +``-incoming file:filename``
> +    Accept incoming migration from a given file.
>  
>  ``-incoming exec:cmdline``
>      Accept incoming migration as an output from specified external
> -- 
> 1.8.3.1
> 

-- 
Peter Xu

Re: [PATCH V3 1/2] migration: file URI

[Peter Xu]

On Wed, Jun 28, 2023 at 01:07:24PM -0400, Peter Xu wrote:
> On Thu, Jun 22, 2023 at 01:37:30PM -0700, Steve Sistare wrote:
> > Extend the migration URI to support file:<filename>.  This can be used for
> > any migration scenario that does not require a reverse path.  It can be
> > used as an alternative to 'exec:cat > file' in minimized containers that
> > do not contain /bin/sh, and it is easier to use than the fd:<fdname> URI.
> > It can be used in HMP commands, and as a qemu command-line parameter.
> > 
> > For best performance, guest ram should be shared and x-ignore-shared
> > should be true, so guest pages are not written to the file, in which case
> > the guest may remain running.  If ram is not so configured, then the user
> > is advised to stop the guest first.  Otherwise, a busy guest may re-dirty
> > the same page, causing it to be appended to the file multiple times,
> > and the file may grow unboundedly.  That issue is being addressed in the
> > "fixed-ram" patch series.
> > 
> > Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
> > Reviewed-by: Fabiano Rosas <farosas@suse.de>
> > ---
> >  migration/file.c       | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  migration/file.h       | 14 ++++++++++++
> >  migration/meson.build  |  1 +
> >  migration/migration.c  |  5 ++++
> >  migration/trace-events |  4 ++++
> >  qemu-options.hx        |  6 ++++-
> >  6 files changed, 91 insertions(+), 1 deletion(-)
> >  create mode 100644 migration/file.c
> >  create mode 100644 migration/file.h
> > 
> > diff --git a/migration/file.c b/migration/file.c
> > new file mode 100644
> > index 0000000..8e35827
> > --- /dev/null
> > +++ b/migration/file.c
> > @@ -0,0 +1,62 @@
> > +/*
> > + * Copyright (c) 2021-2023 Oracle and/or its affiliates.
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2.
> > + * See the COPYING file in the top-level directory.
> > + */
> > +
> > +#include "qemu/osdep.h"
> > +#include "channel.h"
> > +#include "file.h"
> > +#include "migration.h"
> > +#include "io/channel-file.h"
> > +#include "io/channel-util.h"
> > +#include "trace.h"
> > +
> > +void file_start_outgoing_migration(MigrationState *s, const char *filename,
> > +                                   Error **errp)
> > +{
> > +    g_autoptr(QIOChannelFile) fioc = NULL;
> > +    QIOChannel *ioc;
> > +
> > +    trace_migration_file_outgoing(filename);
> > +
> > +    fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
> > +                                     0600, errp);
> > +    if (!fioc) {
> > +        return;
> > +    }
> > +
> > +    ioc = QIO_CHANNEL(fioc);
> > +    qio_channel_set_name(ioc, "migration-file-outgoing");
> > +    migration_channel_connect(s, ioc, NULL, NULL);
> 
> Miss one object_unref(ioc)?

Never mind, I overlooked the g_autoptr.. all fine:

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu

[PATCH V3 2/2] migration: file URI offset

[Steve Sistare]

Allow an offset option to be specified as part of the file URI, in
the form "file:filename,offset=offset", where offset accepts the common
size suffixes, or the 0x prefix, but not both.  Migration data is written
to and read from the file starting at offset.  If unspecified, it defaults
to 0.

This is needed by libvirt to store its own data at the head of the file.

Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 migration/file.c | 45 +++++++++++++++++++++++++++++++++++++++++++--
 qemu-options.hx  |  7 ++++---
 2 files changed, 47 insertions(+), 5 deletions(-)

diff --git a/migration/file.c b/migration/file.c
index 8e35827..8960be9 100644
--- a/migration/file.c
+++ b/migration/file.c
@@ -6,6 +6,8 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/cutils.h"
+#include "qapi/error.h"
 #include "channel.h"
 #include "file.h"
 #include "migration.h"
@@ -13,14 +15,41 @@
 #include "io/channel-util.h"
 #include "trace.h"
 
-void file_start_outgoing_migration(MigrationState *s, const char *filename,
+#define OFFSET_OPTION ",offset="
+
+/* Remove the offset option from @filespec and return it in @offsetp. */
+
+static int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp)
+{
+    char *option = strstr(filespec, OFFSET_OPTION);
+    int ret;
+
+    if (option) {
+        *option = 0;
+        option += sizeof(OFFSET_OPTION) - 1;
+        ret = qemu_strtosz(option, NULL, offsetp);
+        if (ret) {
+            error_setg_errno(errp, ret, "file URI has bad offset %s", option);
+            return -1;
+        }
+    }
+    return 0;
+}
+
+void file_start_outgoing_migration(MigrationState *s, const char *filespec,
                                    Error **errp)
 {
+    g_autofree char *filename = g_strdup(filespec);
     g_autoptr(QIOChannelFile) fioc = NULL;
+    uint64_t offset = 0;
     QIOChannel *ioc;
 
     trace_migration_file_outgoing(filename);
 
+    if (file_parse_offset(filename, &offset, errp)) {
+        return;
+    }
+
     fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
                                      0600, errp);
     if (!fioc) {
@@ -28,6 +57,9 @@ void file_start_outgoing_migration(MigrationState *s, const char *filename,
     }
 
     ioc = QIO_CHANNEL(fioc);
+    if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
+        return;
+    }
     qio_channel_set_name(ioc, "migration-file-outgoing");
     migration_channel_connect(s, ioc, NULL, NULL);
 }
@@ -41,19 +73,28 @@ static gboolean file_accept_incoming_migration(QIOChannel *ioc,
     return G_SOURCE_REMOVE;
 }
 
-void file_start_incoming_migration(const char *filename, Error **errp)
+void file_start_incoming_migration(const char *filespec, Error **errp)
 {
+    g_autofree char *filename = g_strdup(filespec);
     QIOChannelFile *fioc = NULL;
+    uint64_t offset = 0;
     QIOChannel *ioc;
 
     trace_migration_file_incoming(filename);
 
+    if (file_parse_offset(filename, &offset, errp)) {
+        return;
+    }
+
     fioc = qio_channel_file_new_path(filename, O_RDONLY, 0, errp);
     if (!fioc) {
         return;
     }
 
     ioc = QIO_CHANNEL(fioc);
+    if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
+        return;
+    }
     qio_channel_set_name(QIO_CHANNEL(ioc), "migration-file-incoming");
     qio_channel_add_watch_full(ioc, G_IO_IN,
                                file_accept_incoming_migration,
diff --git a/qemu-options.hx b/qemu-options.hx
index 5aab8fb..5a92210 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4622,7 +4622,7 @@ DEF("incoming", HAS_ARG, QEMU_OPTION_incoming, \
     "                prepare for incoming migration, listen on\n" \
     "                specified protocol and socket address\n" \
     "-incoming fd:fd\n" \
-    "-incoming file:filename\n" \
+    "-incoming file:filename[,offset=offset]\n" \
     "-incoming exec:cmdline\n" \
     "                accept incoming migration on given file descriptor\n" \
     "                or from given external command\n" \
@@ -4641,8 +4641,9 @@ SRST
 ``-incoming fd:fd``
     Accept incoming migration from a given file descriptor.
 
-``-incoming file:filename``
-    Accept incoming migration from a given file.
+``-incoming file:filename[,offset=offset]``
+    Accept incoming migration from a given file starting at offset.
+    offset allows the common size suffixes, or a 0x prefix, but not both.
 
 ``-incoming exec:cmdline``
     Accept incoming migration as an output from specified external
-- 
1.8.3.1

Re: [PATCH V3 2/2] migration: file URI offset

[Peter Xu]

On Thu, Jun 22, 2023 at 01:37:31PM -0700, Steve Sistare wrote:
> Allow an offset option to be specified as part of the file URI, in
> the form "file:filename,offset=offset", where offset accepts the common
> size suffixes, or the 0x prefix, but not both.  Migration data is written
> to and read from the file starting at offset.  If unspecified, it defaults
> to 0.
> 
> This is needed by libvirt to store its own data at the head of the file.
> 
> Suggested-by: Daniel P. Berrange <berrange@redhat.com>
> Signed-off-by: Steve Sistare <steven.sistare@oracle.com>

Ideally I think we should make "," the separator from the start, but I
suppose no one will try to apply previous patch only, and then start using
a file name contains ",offset=".. so maybe not that a huge deal.

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu

Re: [PATCH V3 2/2] migration: file URI offset

[Peter Xu]

On Thu, Jun 22, 2023 at 01:37:31PM -0700, Steve Sistare wrote:
> +static int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp)
> +{
> +    char *option = strstr(filespec, OFFSET_OPTION);
> +    int ret;
> +
> +    if (option) {
> +        *option = 0;
> +        option += sizeof(OFFSET_OPTION) - 1;
> +        ret = qemu_strtosz(option, NULL, offsetp);
> +        if (ret) {
> +            error_setg_errno(errp, ret, "file URI has bad offset %s", option);

Probably "-ret" here.

> +            return -1;
> +        }
> +    }
> +    return 0;
> +}

-- 
Peter Xu

Re: [PATCH V3 2/2] migration: file URI offset

[Steven Sistare]

On 6/29/2023 5:38 PM, Peter Xu wrote:
> On Thu, Jun 22, 2023 at 01:37:31PM -0700, Steve Sistare wrote:
>> +static int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp)
>> +{
>> +    char *option = strstr(filespec, OFFSET_OPTION);
>> +    int ret;
>> +
>> +    if (option) {
>> +        *option = 0;
>> +        option += sizeof(OFFSET_OPTION) - 1;
>> +        ret = qemu_strtosz(option, NULL, offsetp);
>> +        if (ret) {
>> +            error_setg_errno(errp, ret, "file URI has bad offset %s", option);
> 
> Probably "-ret" here.

Yes, thanks.

I have submitted V4 with this fix and your RB's appended.

- Steve