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[Qemu-devel] [PULL 10/41] char: chardevice hotswap
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 10/41] char: chardevice hotswap |
Date: |
Thu, 13 Jul 2017 16:24:03 +0200 |
From: Anton Nefedov <address@hidden>
This patch adds a possibility to change a char device without a frontend
removal.
Ideally, it would have to happen transparently to a frontend, i.e.
frontend would continue its regular operation.
However, backends are not stateless and are set up by the frontends
via qemu_chr_fe_<> functions, and it's not (generally) possible to replay
that setup entirely in a backend code, as different chardevs respond
to the setup calls differently, so do frontends work differently basing
on those setup responses.
Moreover, some frontend can generally get and save the backend pointer
(qemu_chr_fe_get_driver()), and it will become invalid after backend change.
So, a frontend which would like to support chardev hotswap has to register
a "backend change" handler, and redo its backend setup there.
Signed-off-by: Anton Nefedov <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
Message-Id: <address@hidden>
Reviewed-by: Marc-André Lureau <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
chardev/char.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/chardev/char.h | 9 ++++++
qapi-schema.json | 40 ++++++++++++++++++++++++
3 files changed, 132 insertions(+)
diff --git a/chardev/char.c b/chardev/char.c
index 839eff6..d6b9d89 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -951,6 +951,89 @@ ChardevReturn *qmp_chardev_add(const char *id,
ChardevBackend *backend,
return ret;
}
+ChardevReturn *qmp_chardev_change(const char *id, ChardevBackend *backend,
+ Error **errp)
+{
+ CharBackend *be;
+ const ChardevClass *cc;
+ Chardev *chr, *chr_new;
+ bool closed_sent = false;
+ ChardevReturn *ret;
+
+ chr = qemu_chr_find(id);
+ if (!chr) {
+ error_setg(errp, "Chardev '%s' does not exist", id);
+ return NULL;
+ }
+
+ if (CHARDEV_IS_MUX(chr)) {
+ error_setg(errp, "Mux device hotswap not supported yet");
+ return NULL;
+ }
+
+ if (qemu_chr_replay(chr)) {
+ error_setg(errp,
+ "Chardev '%s' cannot be changed in record/replay mode", id);
+ return NULL;
+ }
+
+ be = chr->be;
+ if (!be) {
+ /* easy case */
+ object_unparent(OBJECT(chr));
+ return qmp_chardev_add(id, backend, errp);
+ }
+
+ if (!be->chr_be_change) {
+ error_setg(errp, "Chardev user does not support chardev hotswap");
+ return NULL;
+ }
+
+ cc = char_get_class(ChardevBackendKind_lookup[backend->type], errp);
+ if (!cc) {
+ return NULL;
+ }
+
+ chr_new = qemu_chardev_new(NULL, object_class_get_name(OBJECT_CLASS(cc)),
+ backend, errp);
+ if (!chr_new) {
+ return NULL;
+ }
+ chr_new->label = g_strdup(id);
+
+ if (chr->be_open && !chr_new->be_open) {
+ qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
+ closed_sent = true;
+ }
+
+ chr->be = NULL;
+ qemu_chr_fe_init(be, chr_new, &error_abort);
+
+ if (be->chr_be_change(be->opaque) < 0) {
+ error_setg(errp, "Chardev '%s' change failed", chr_new->label);
+ chr_new->be = NULL;
+ qemu_chr_fe_init(be, chr, &error_abort);
+ if (closed_sent) {
+ qemu_chr_be_event(chr, CHR_EVENT_OPENED);
+ }
+ object_unref(OBJECT(chr_new));
+ return NULL;
+ }
+
+ object_unparent(OBJECT(chr));
+ object_property_add_child(get_chardevs_root(), chr_new->label,
+ OBJECT(chr_new), &error_abort);
+ object_unref(OBJECT(chr_new));
+
+ ret = g_new0(ChardevReturn, 1);
+ if (CHARDEV_IS_PTY(chr_new)) {
+ ret->pty = g_strdup(chr_new->filename + 4);
+ ret->has_pty = true;
+ }
+
+ return ret;
+}
+
void qmp_chardev_remove(const char *id, Error **errp)
{
Chardev *chr;
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 8a9ade4..22fd734 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -93,6 +93,15 @@ void qemu_chr_parse_common(QemuOpts *opts, ChardevCommon
*backend);
Chardev *qemu_chr_new(const char *label, const char *filename);
/**
+ * @qemu_chr_change:
+ *
+ * Change an existing character backend
+ *
+ * @opts the new backend options
+ */
+void qemu_chr_change(QemuOpts *opts, Error **errp);
+
+/**
* @qemu_chr_cleanup:
*
* Delete all chardevs (when leaving qemu)
diff --git a/qapi-schema.json b/qapi-schema.json
index 37c4b95..0090fbf 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -5098,6 +5098,46 @@
'returns': 'ChardevReturn' }
##
+# @chardev-change:
+#
+# Change a character device backend
+#
+# @id: the chardev's ID, must exist
+# @backend: new backend type and parameters
+#
+# Returns: ChardevReturn.
+#
+# Since: 2.10
+#
+# Example:
+#
+# -> { "execute" : "chardev-change",
+# "arguments" : { "id" : "baz",
+# "backend" : { "type" : "pty", "data" : {} } } }
+# <- { "return": { "pty" : "/dev/pty/42" } }
+#
+# -> {"execute" : "chardev-change",
+# "arguments" : {
+# "id" : "charchannel2",
+# "backend" : {
+# "type" : "socket",
+# "data" : {
+# "addr" : {
+# "type" : "unix" ,
+# "data" : {
+# "path" : "/tmp/charchannel2.socket"
+# }
+# },
+# "server" : true,
+# "wait" : false }}}}
+# <- {"return": {}}
+#
+##
+{ 'command': 'chardev-change', 'data': {'id' : 'str',
+ 'backend' : 'ChardevBackend' },
+ 'returns': 'ChardevReturn' }
+
+##
# @chardev-remove:
#
# Remove a character device backend
--
1.8.3.1
- [Qemu-devel] [PULL 00/41] Misc patches for QEMU 2.10 soft freeze, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 04/41] MAINTAINERS: update Xen entries, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 03/41] MAINTAINERS: update KVM entries, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 01/41] build: add -Wexpansion-to-defined, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 06/41] MAINTAINERS: add entry for "Unimplemented" device, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 02/41] MAINTAINERS: update TCG entries, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 07/41] chardev: block during sync read, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 05/41] MAINTAINERS: update TCI entry, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 08/41] char: move QemuOpts->ChardevBackend translation to a separate func, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 10/41] char: chardevice hotswap,
Paolo Bonzini <=
- [Qemu-devel] [PULL 13/41] test-char: destroy chardev-udp after test, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 12/41] char: avoid chardevice direct access, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 16/41] test-char: add hotswap test, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 14/41] test-char: split char_udp_test, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 17/41] hmp: add hmp analogue for qmp-chardev-change, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 15/41] test-char: split char_file_test, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 19/41] serial: move TIOCM update to a separate function, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 21/41] exec: use qemu_ram_ptr_length to access guest ram, Paolo Bonzini, 2017/07/13
- [Qemu-devel] [PULL 23/41] mttcg/i386: Patch instruction using async_safe_* framework, Paolo Bonzini, 2017/07/13