[libvirt] [PATCH v4 4/4] qemu-config: Add new -add-fd command line option
Corey Bryant
coreyb at linux.vnet.ibm.com
Thu Oct 18 19:19:34 UTC 2012
This option can be used for passing file descriptors on the
command line. It mirrors the existing add-fd QMP command which
allows an fd to be passed to QEMU via SCM_RIGHTS and added to an
fd set.
This can be combined with commands such as -drive to link file
descriptors in an fd set to a drive:
qemu-kvm -add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
-drive file=/dev/fdset/2,index=0,media=disk
This example adds dups of fds 3 and 4, and the accompanying opaque
strings to the fd set with ID=2. qemu_open() already knows how
to handle a filename of this format. qemu_open() searches the
corresponding fd set for an fd and when it finds a match, QEMU
goes on to use a dup of that fd just like it would have used an
fd that it opened itself.
Signed-off-by: Corey Bryant <coreyb at linux.vnet.ibm.com>
---
v2:
- The -add-fd option is new in v2 (eblake at redhat.com)
v3:
- Require passed fd to be > stderr (eblake at redhat.com)
- Changed fds in examples to fd=3 and fd=4
- Add dup of passed fd to fd set and close passed fds after
processing all -add-fd commands (eblake at redhat.com)
v4
- Update fd numbers in commit message text (eblake at redhat.com)
- Handle corner case of -add-fd using an fd that is already
in use by QEMU (eblake at redhat.com)
qemu-config.c | 22 ++++++++++++++++
qemu-options.hx | 36 ++++++++++++++++++++++++++
vl.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 136 insertions(+)
diff --git a/qemu-config.c b/qemu-config.c
index cd1ec21..601237d 100644
--- a/qemu-config.c
+++ b/qemu-config.c
@@ -653,6 +653,27 @@ QemuOptsList qemu_boot_opts = {
},
};
+static QemuOptsList qemu_add_fd_opts = {
+ .name = "add-fd",
+ .head = QTAILQ_HEAD_INITIALIZER(qemu_add_fd_opts.head),
+ .desc = {
+ {
+ .name = "fd",
+ .type = QEMU_OPT_NUMBER,
+ .help = "file descriptor of which a duplicate is added to fd set",
+ },{
+ .name = "set",
+ .type = QEMU_OPT_NUMBER,
+ .help = "ID of the fd set to add fd to",
+ },{
+ .name = "opaque",
+ .type = QEMU_OPT_STRING,
+ .help = "free-form string used to describe fd",
+ },
+ { /* end of list */ }
+ },
+};
+
static QemuOptsList *vm_config_groups[32] = {
&qemu_drive_opts,
&qemu_chardev_opts,
@@ -669,6 +690,7 @@ static QemuOptsList *vm_config_groups[32] = {
&qemu_boot_opts,
&qemu_iscsi_opts,
&qemu_sandbox_opts,
+ &qemu_add_fd_opts,
NULL,
};
diff --git a/qemu-options.hx b/qemu-options.hx
index 7d97f96..a70182a 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -257,6 +257,14 @@ qemu-system-i386 -drive file=file,index=2,media=disk
qemu-system-i386 -drive file=file,index=3,media=disk
@end example
+You can open an image using pre-opened file descriptors from an fd set:
+ at example
+qemu-system-i386
+-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
+-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
+-drive file=/dev/fdset/2,index=0,media=disk
+ at end example
+
You can connect a CDROM to the slave of ide0:
@example
qemu-system-i386 -drive file=file,if=ide,index=1,media=cdrom
@@ -289,6 +297,34 @@ qemu-system-i386 -hda a -hdb b
@end example
ETEXI
+DEF("add-fd", HAS_ARG, QEMU_OPTION_add_fd,
+ "-add-fd fd=fd,set=set[,opaque=opaque]\n"
+ " Add 'fd' to fd 'set'\n", QEMU_ARCH_ALL)
+STEXI
+ at item -add-fd fd=@var{fd},set=@var{set}[,opaque=@var{opaque}]
+ at findex -add-fd
+
+Add a file descriptor to an fd set. Valid options are:
+
+ at table @option
+ at item fd=@var{fd}
+This option defines the file descriptor of which a duplicate is added to fd set.
+The file descriptor cannot be stdin, stdout, or stderr.
+ at item set=@var{set}
+This option defines the ID of the fd set to add the file descriptor to.
+ at item opaque=@var{opaque}
+This option defines a free-form string that can be used to describe @var{fd}.
+ at end table
+
+You can open an image using pre-opened file descriptors from an fd set:
+ at example
+qemu-system-i386
+-add-fd fd=3,set=2,opaque="rdwr:/path/to/file"
+-add-fd fd=4,set=2,opaque="rdonly:/path/to/file"
+-drive file=/dev/fdset/2,index=0,media=disk
+ at end example
+ETEXI
+
DEF("set", HAS_ARG, QEMU_OPTION_set,
"-set group.id.arg=value\n"
" set <arg> parameter for item <id> of type <group>\n"
diff --git a/vl.c b/vl.c
index 5b357a3..47095a2 100644
--- a/vl.c
+++ b/vl.c
@@ -790,6 +790,71 @@ static int parse_sandbox(QemuOpts *opts, void *opaque)
return 0;
}
+static int parse_add_fd(QemuOpts *opts, void *opaque)
+{
+ int fd, dupfd;
+ int64_t fdset_id;
+ const char *fd_opaque = NULL;
+
+ fd = qemu_opt_get_number(opts, "fd", -1);
+ fdset_id = qemu_opt_get_number(opts, "set", -1);
+ fd_opaque = qemu_opt_get(opts, "opaque");
+
+ if (fd < 0) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd option is required and must be non-negative");
+ return -1;
+ }
+
+ if (fd <= STDERR_FILENO) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd cannot be a standard I/O stream");
+ return -1;
+ }
+
+ if (fcntl(fd, F_GETFD) & FD_CLOEXEC) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "fd is not valid or already in use");
+ return -1;
+ }
+
+ if (fdset_id < 0) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "set option is required and must be non-negative");
+ return -1;
+ }
+
+#ifdef F_DUPFD_CLOEXEC
+ dupfd = fcntl(fd, F_DUPFD_CLOEXEC, 0);
+#else
+ dupfd = dup(fd);
+ if (dupfd != -1) {
+ qemu_set_cloexec(dupfd);
+ }
+#endif
+ if (dupfd == -1) {
+ qerror_report(ERROR_CLASS_GENERIC_ERROR,
+ "Error duplicating fd: %s", strerror(errno));
+ return -1;
+ }
+
+ /* add the duplicate fd, and optionally the opaque string, to the fd set */
+ monitor_fdset_add_fd(dupfd, true, fdset_id, fd_opaque ? true : false,
+ fd_opaque, NULL);
+
+ return 0;
+}
+
+static int cleanup_add_fd(QemuOpts *opts, void *opaque)
+{
+ int fd;
+
+ fd = qemu_opt_get_number(opts, "fd", -1);
+ close(fd);
+
+ return 0;
+}
+
/***********************************************************/
/* QEMU Block devices */
@@ -3309,6 +3374,11 @@ int main(int argc, char **argv, char **envp)
exit(0);
}
break;
+ case QEMU_OPTION_add_fd:
+ opts = qemu_opts_parse(qemu_find_opts("add-fd"), optarg, 0);
+ if (!opts) {
+ exit(0);
+ }
default:
os_parse_cmd_args(popt->index, optarg);
}
@@ -3320,6 +3390,14 @@ int main(int argc, char **argv, char **envp)
exit(1);
}
+ if (qemu_opts_foreach(qemu_find_opts("add-fd"), parse_add_fd, NULL, 1)) {
+ exit(1);
+ }
+
+ if (qemu_opts_foreach(qemu_find_opts("add-fd"), cleanup_add_fd, NULL, 1)) {
+ exit(1);
+ }
+
if (machine == NULL) {
fprintf(stderr, "No machine found.\n");
exit(1);
--
1.7.11.4
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