| Message ID | 1499342940-56739-4-git-send-email-anton.nefedov@virtuozzo.com |
|---|---|
| State | New |
| Headers | show |
On Thu, Jul 6, 2017 at 5:08 AM, Anton Nefedov <anton.nefedov@virtuozzo.com> wrote: > 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 <anton.nefedov@virtuozzo.com> > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> > --- > include/chardev/char.h | 9 ++++++ > chardev/char.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++ > qapi-schema.json | 40 ++++++++++++++++++++++++ > 3 files changed, 132 insertions(+) > > 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/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/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 > -- > 2.7.4 > >
On Thu, Jul 6, 2017 at 5:08 AM, Anton Nefedov <anton.nefedov@virtuozzo.com> wrote: > 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 <anton.nefedov@virtuozzo.com> > Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com> > --- > include/chardev/char.h | 9 ++++++ > chardev/char.c | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++ > qapi-schema.json | 40 ++++++++++++++++++++++++ > 3 files changed, 132 insertions(+) > > 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/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/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 > -- > 2.7.4 > >
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/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/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