On a Wednesday in 2022, Peter Krempa wrote:
The existing helpers we have are very clumsy and there's no integration with the monitor. This patch introduces new helpers to bridge the gap and simplify handing
*handling
of fdsets and classic FD passing when generating commandline/hotplug arguments. Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx> --- po/POTFILES.in | 1 + src/qemu/meson.build | 1 + src/qemu/qemu_fd.c | 296 +++++++++++++++++++++++++++++++++++++++++++ src/qemu/qemu_fd.h | 56 ++++++++ 4 files changed, 354 insertions(+) create mode 100644 src/qemu/qemu_fd.c create mode 100644 src/qemu/qemu_fd.h diff --git a/po/POTFILES.in b/po/POTFILES.in index bf0a3b3529..1fd3afdd6f 100644 --- a/po/POTFILES.in +++ b/po/POTFILES.in @@ -164,6 +164,7 @@ @SRCDIR@src/qemu/qemu_domainjob.c @SRCDIR@src/qemu/qemu_driver.c @SRCDIR@src/qemu/qemu_extdevice.c +@SRCDIR@src/qemu/qemu_fd.c @SRCDIR@src/qemu/qemu_firmware.c @SRCDIR@src/qemu/qemu_hostdev.c @SRCDIR@src/qemu/qemu_hotplug.c diff --git a/src/qemu/meson.build b/src/qemu/meson.build index 3ea084cff8..39f0f615cc 100644 --- a/src/qemu/meson.build +++ b/src/qemu/meson.build @@ -15,6 +15,7 @@ qemu_driver_sources = [ 'qemu_domainjob.c', 'qemu_driver.c', 'qemu_extdevice.c', + 'qemu_fd.c', 'qemu_firmware.c', 'qemu_hostdev.c', 'qemu_hotplug.c', diff --git a/src/qemu/qemu_fd.c b/src/qemu/qemu_fd.c new file mode 100644 index 0000000000..4052323cb0 --- /dev/null +++ b/src/qemu/qemu_fd.c @@ -0,0 +1,296 @@ +/* + * qemu_fd.c: QEMU fd and fdpass passing helpers + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>.
I believe that for new code, all we need is: SPDX-License-Identifier: LGPL-2.1-or-later (which is shorter and easier to read, but will be inconsistent)
+ */ + +#include <config.h> + +#include "qemu_fd.h" +#include "qemu_domain.h" + +#include "viralloc.h" +#include "virfile.h" +#include "virlog.h"
+/** + * qemuFDPassNew: + * @prefix: prefix used for naming the passed FDs + * @dompriv: qemu domain private data + * @useFDSet: Always use FD sets (/dev/fdset/N) for this instance + * + * Create a new helper object for passing FDs to qemu. If @useFDSet is false + * the older approach of directly using FD number on the commandline and 'getfd' + * QMP command is used. Otherwise '-add-fd' and /dev/fdset/N is used to pass the + * FD. + *
I dislike using bools in helpers, can this be turned into a flag? Alternatively, to discourage the older approach you can create a thin qemuFDPassNewLegacy wrapper and leave qemuFDPassNew without the comment. (Can we even convince QEMU to use fdset for sockets? Or is that not worth pursuing?)
+ * Non-test uses must pass a valid @dompriv.
+ *
+ * @prefix is used for naming the FD if needed and is later referenced when
+ * removing the FDSet via monitor.
+ */
+qemuFDPass *
+qemuFDPassNew(const char *prefix,
+ void *dompriv,
+ bool useFDSet)
+{
+ qemuDomainObjPrivate *priv = dompriv;
+ qemuFDPass *fdpass = g_new0(qemuFDPass, 1);
+
+ fdpass->prefix = g_strdup(prefix);
+ fdpass->useFDSet = useFDSet;
+
+ if (fdpass->useFDSet && priv)
+ fdpass->fdSetID = qemuDomainFDSetIdNew(priv);
+
+ return fdpass;
+}
+
+
+/**
+ * qemuFDPassAddFD:
+ * @fdpass: The fd passing helper struct
+ * @fd: File descriptor to pass
+ * @suffix: Name suffix for the file descriptor name
+ *
+ * Adds @fd to be passed to qemu when transferring @fdpass to qemu.
QEMU
When @fdpass
+ * is configured to use FD set mode, multiple file descriptors can be passed by
+ * calling this function repeatedly.
+ *
+ * @suffix is used to build the name of the file descriptor by concatenating
+ * it with @prefix passed to qemuFDPassNew. @suffix may be NULL, in which case
+ * it's considered to be an empty string.
+ *
+ * Returns 0 on success, -1 on error (when attempting to pass multiple FDs) using
+ * the 'direct' method.
+ */
+int
+qemuFDPassAddFD(qemuFDPass *fdpass,
+ int *fd,
+ const char *suffix)
+{
+ struct qemuFDPassFD newfd = { .fd = *fd };
+
+ if (newfd.fd < 0) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("invalid file descriptor"));
+ return -1;
+ }
+
+ if (fdpass->nfds >= 1) {
+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+ _("direct FD passing supports only 1 file descriptor"));
This check conflicts with the comment above saying multiple FDs are allowed with fdsets. Also, please s/1/one/
+ return -1;
+ }
+
+ *fd = -1;
+
+ newfd.opaque = g_strdup_printf("%s%s", fdpass->prefix, NULLSTR_EMPTY(suffix));
+
+ VIR_APPEND_ELEMENT(fdpass->fds, fdpass->nfds, newfd);
+
+ return 0;
+}
Reviewed-by: Ján Tomko <jtomko@xxxxxxxxxx> Jano
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