Patchwork [v5] qemu-config: Add new -add-fd command line option

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Submitter Kevin Wolf
Date Oct. 22, 2012, 2:36 p.m.
Message ID <1350916563-15700-1-git-send-email-kwolf@redhat.com>
Download mbox | patch
Permalink /patch/193163/
State New
Headers show

Comments

Kevin Wolf - Oct. 22, 2012, 2:36 p.m.
From: Corey Bryant <coreyb@linux.vnet.ibm.com>

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@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---

Sorry, Corey, hope you're okay with me taking over your patch... Your patch was
against the unmodified version while I already did some changes after the v4
review, so it didn't apply.

This version just completely disables fd passing on Windows as I don't think
it works there anyway. Gives you a nice error message instead of a silently
ignored -add-fd option.

Also added the missing break for case QEMU_OPTION_add_fd.

 qemu-config.c   |   22 +++++++++++++
 qemu-options.hx |   36 +++++++++++++++++++++
 vl.c            |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 152 insertions(+), 0 deletions(-)
Corey Bryant - Oct. 22, 2012, 3:06 p.m.
On 10/22/2012 10:36 AM, Kevin Wolf wrote:
> From: Corey Bryant <coreyb@linux.vnet.ibm.com>
>
> 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@linux.vnet.ibm.com>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>
> Sorry, Corey, hope you're okay with me taking over your patch... Your patch was
> against the unmodified version while I already did some changes after the v4
> review, so it didn't apply.
>

That's fine.  Thanks for the hand.

> This version just completely disables fd passing on Windows as I don't think
> it works there anyway. Gives you a nice error message instead of a silently
> ignored -add-fd option.
>
> Also added the missing break for case QEMU_OPTION_add_fd.
>
>   qemu-config.c   |   22 +++++++++++++
>   qemu-options.hx |   36 +++++++++++++++++++++
>   vl.c            |   94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 152 insertions(+), 0 deletions(-)
>
> 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 46f0539..a67a255 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -253,6 +253,14 @@ 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:
> +@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
> +@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
> @@ -285,6 +293,34 @@ 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
> +@item -add-fd fd=@var{fd},set=@var{set}[,opaque=@var{opaque}]
> +@findex -add-fd
> +
> +Add a file descriptor to an fd set.  Valid options are:
> +
> +@table @option
> +@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.
> +@item set=@var{set}
> +This option defines the ID of the fd set to add the file descriptor to.
> +@item opaque=@var{opaque}
> +This option defines a free-form string that can be used to describe @var{fd}.
> +@end table
> +
> +You can open an image using pre-opened file descriptors from an fd set:
> +@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
> +@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 ee3c43a..b870caf 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -790,6 +790,78 @@ static int parse_sandbox(QemuOpts *opts, void *opaque)
>       return 0;
>   }
>
> +#ifndef _WIN32
> +static int parse_add_fd(QemuOpts *opts, void *opaque)
> +{
> +    int fd, dupfd, flags;
> +    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;
> +    }
> +
> +    /*
> +     * All fds inherited across exec() necessarily have FD_CLOEXEC
> +     * clear, while qemu sets FD_CLOEXEC on all other fds used internally.
> +     */
> +    flags = fcntl(fd, F_GETFD);
> +    if (flags == -1 || (flags & 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;
> +}
> +#endif
> +
>   /***********************************************************/
>   /* QEMU Block devices */
>
> @@ -3309,6 +3381,18 @@ int main(int argc, char **argv, char **envp)
>                       exit(0);
>                   }
>                   break;
> +            case QEMU_OPTION_add_fd:
> +#ifndef _WIN32
> +                opts = qemu_opts_parse(qemu_find_opts("add-fd"), optarg, 0);
> +                if (!opts) {
> +                    exit(0);
> +                }
> +#else
> +                error_report("File descriptor passing is disabled on this "
> +                             "platform");
> +                exit(1);
> +#endif
> +                break;
>               default:
>                   os_parse_cmd_args(popt->index, optarg);
>               }
> @@ -3320,6 +3404,16 @@ int main(int argc, char **argv, char **envp)
>           exit(1);
>       }
>
> +#ifndef _WIN32
> +    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);
> +    }
> +#endif
> +
>       if (machine == NULL) {
>           fprintf(stderr, "No machine found.\n");
>           exit(1);
>

This looks good to me.

Patch

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 46f0539..a67a255 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -253,6 +253,14 @@  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:
+@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
+@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
@@ -285,6 +293,34 @@  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
+@item -add-fd fd=@var{fd},set=@var{set}[,opaque=@var{opaque}]
+@findex -add-fd
+
+Add a file descriptor to an fd set.  Valid options are:
+
+@table @option
+@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.
+@item set=@var{set}
+This option defines the ID of the fd set to add the file descriptor to.
+@item opaque=@var{opaque}
+This option defines a free-form string that can be used to describe @var{fd}.
+@end table
+
+You can open an image using pre-opened file descriptors from an fd set:
+@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
+@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 ee3c43a..b870caf 100644
--- a/vl.c
+++ b/vl.c
@@ -790,6 +790,78 @@  static int parse_sandbox(QemuOpts *opts, void *opaque)
     return 0;
 }
 
+#ifndef _WIN32
+static int parse_add_fd(QemuOpts *opts, void *opaque)
+{
+    int fd, dupfd, flags;
+    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;
+    }
+
+    /*
+     * All fds inherited across exec() necessarily have FD_CLOEXEC
+     * clear, while qemu sets FD_CLOEXEC on all other fds used internally.
+     */
+    flags = fcntl(fd, F_GETFD);
+    if (flags == -1 || (flags & 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;
+}
+#endif
+
 /***********************************************************/
 /* QEMU Block devices */
 
@@ -3309,6 +3381,18 @@  int main(int argc, char **argv, char **envp)
                     exit(0);
                 }
                 break;
+            case QEMU_OPTION_add_fd:
+#ifndef _WIN32
+                opts = qemu_opts_parse(qemu_find_opts("add-fd"), optarg, 0);
+                if (!opts) {
+                    exit(0);
+                }
+#else
+                error_report("File descriptor passing is disabled on this "
+                             "platform");
+                exit(1);
+#endif
+                break;
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }
@@ -3320,6 +3404,16 @@  int main(int argc, char **argv, char **envp)
         exit(1);
     }
 
+#ifndef _WIN32
+    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);
+    }
+#endif
+
     if (machine == NULL) {
         fprintf(stderr, "No machine found.\n");
         exit(1);