[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PATCH 1/2] chardev: implement backend chardev multiplexing
|
From: |
Roman Penyaev |
|
Subject: |
[PATCH 1/2] chardev: implement backend chardev multiplexing |
|
Date: |
Fri, 13 Sep 2024 18:36:35 +0200 |
This patch implements multiplexing capability of several backend
devices, which opens up an opportunity to use a single frontend
device on the guest, which can be manipulated from several
backend devices.
The idea of the change is trivial: keep list of backend devices
(up to 4), init them on demand and forward data buffer back and
forth.
The following is QEMU command line example:
-chardev socket,path=/tmp/sock,server=on,wait=off,id=sock0 \
-chardev vc,id=vc0 \
-chardev mux,id=mux0,chardev=vc0,,sock0 \
-device virtconsole,chardev=mux0 \
-vnc 0.0.0.0:0
Which creates 2 backend devices: text virtual console (`vc0`)
and a socket (`sock0`) connected to the single virtio hvc
console with the multiplexer (`mux0`) help. `vc0` renders
text to an image, which can be shared over the VNC protocol.
`sock0` is a socket backend which provides biderectional
communication to the virtio hvc console.
Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Cc: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org
---
chardev/char-fe.c | 14 +++--
chardev/char-mux.c | 120 +++++++++++++++++++++++++++++--------
chardev/char.c | 2 +-
chardev/chardev-internal.h | 7 ++-
4 files changed, 111 insertions(+), 32 deletions(-)
diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index b214ba3802b1..d1f67338084d 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -197,16 +197,22 @@ bool qemu_chr_fe_init(CharBackend *b, Chardev *s, Error
**errp)
if (CHARDEV_IS_MUX(s)) {
MuxChardev *d = MUX_CHARDEV(s);
- if (d->mux_cnt >= MAX_MUX) {
+ if (d->fe_cnt >= MAX_MUX) {
error_setg(errp,
"too many uses of multiplexed chardev '%s'"
" (maximum is " stringify(MAX_MUX) ")",
s->label);
return false;
}
-
- d->backends[d->mux_cnt] = b;
- tag = d->mux_cnt++;
+ if (d->fe_cnt > 0 && d->be_cnt > 1) {
+ error_setg(errp,
+ "multiplexed chardev '%s' is already used "
+ "for backend multiplexing",
+ s->label);
+ return false;
+ }
+ d->backends[d->fe_cnt] = b;
+ tag = d->fe_cnt++;
} else if (s->be) {
error_setg(errp, "chardev '%s' is already in use", s->label);
return false;
diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index ee2d47b20d9b..82f728b5caf8 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -26,6 +26,7 @@
#include "qapi/error.h"
#include "qemu/module.h"
#include "qemu/option.h"
+#include "qemu/cutils.h"
#include "chardev/char.h"
#include "sysemu/block-backend.h"
#include "qapi/qapi-commands-control.h"
@@ -40,13 +41,39 @@
*/
static bool muxes_opened = true;
+/* Write to all backends */
+static int mux_chr_fe_write(MuxChardev *mux, const uint8_t *buf, int len)
+{
+ int r, ret = -1, i;
+
+ for (i = 0; i < mux->be_cnt; i++) {
+ r = qemu_chr_fe_write(&mux->chrs[i], buf, len);
+ ret = ret < 0 ? r : MAX(r, ret);
+ }
+
+ return ret;
+}
+
+/* Write to all backends */
+static int mux_chr_fe_write_all(MuxChardev *mux, const uint8_t *buf, int len)
+{
+ int r, ret = -1, i;
+
+ for (i = 0; i < mux->be_cnt; i++) {
+ r = qemu_chr_fe_write_all(&mux->chrs[i], buf, len);
+ ret = ret < 0 ? r : MAX(r, ret);
+ }
+
+ return ret;
+}
+
/* Called with chr_write_lock held. */
static int mux_chr_write(Chardev *chr, const uint8_t *buf, int len)
{
MuxChardev *d = MUX_CHARDEV(chr);
int ret;
if (!d->timestamps) {
- ret = qemu_chr_fe_write(&d->chr, buf, len);
+ ret = mux_chr_fe_write(d, buf, len);
} else {
int i;
@@ -71,11 +98,11 @@ static int mux_chr_write(Chardev *chr, const uint8_t *buf,
int len)
(int)(ti % 1000));
/* XXX this blocks entire thread. Rewrite to use
* qemu_chr_fe_write and background I/O callbacks */
- qemu_chr_fe_write_all(&d->chr,
+ mux_chr_fe_write_all(d,
(uint8_t *)buf1, strlen(buf1));
d->linestart = 0;
}
- ret += qemu_chr_fe_write(&d->chr, buf + i, 1);
+ ret += mux_chr_fe_write(d, buf + i, 1);
if (buf[i] == '\n') {
d->linestart = 1;
}
@@ -168,9 +195,9 @@ static int mux_proc_byte(Chardev *chr, MuxChardev *d, int
ch)
qemu_chr_be_event(chr, CHR_EVENT_BREAK);
break;
case 'c':
- assert(d->mux_cnt > 0); /* handler registered with first fe */
+ assert(d->fe_cnt > 0); /* handler registered with first fe */
/* Switch to the next registered device */
- mux_set_focus(chr, (d->focus + 1) % d->mux_cnt);
+ mux_set_focus(chr, (d->focus + 1) % d->fe_cnt);
break;
case 't':
d->timestamps = !d->timestamps;
@@ -248,8 +275,8 @@ void mux_chr_send_all_event(Chardev *chr, QEMUChrEvent
event)
return;
}
- /* Send the event to all registered listeners */
- for (i = 0; i < d->mux_cnt; i++) {
+ /* Send the event to all registered frontend listeners */
+ for (i = 0; i < d->fe_cnt; i++) {
mux_chr_send_event(d, i, event);
}
}
@@ -262,8 +289,16 @@ static void mux_chr_event(void *opaque, QEMUChrEvent event)
static GSource *mux_chr_add_watch(Chardev *s, GIOCondition cond)
{
MuxChardev *d = MUX_CHARDEV(s);
- Chardev *chr = qemu_chr_fe_get_driver(&d->chr);
- ChardevClass *cc = CHARDEV_GET_CLASS(chr);
+ Chardev *chr;
+ ChardevClass *cc;
+
+ if (d->be_cnt > 1) {
+ /* TODO: multiple backends have to be combined on a single watch */
+ return NULL;
+ }
+
+ chr = qemu_chr_fe_get_driver(&d->chrs[0]);
+ cc = CHARDEV_GET_CLASS(chr);
if (!cc->chr_add_watch) {
return NULL;
@@ -277,27 +312,32 @@ static void char_mux_finalize(Object *obj)
MuxChardev *d = MUX_CHARDEV(obj);
int i;
- for (i = 0; i < d->mux_cnt; i++) {
+ for (i = 0; i < d->fe_cnt; i++) {
CharBackend *be = d->backends[i];
if (be) {
be->chr = NULL;
}
}
- qemu_chr_fe_deinit(&d->chr, false);
+ for (i = 0; i < d->be_cnt; i++) {
+ qemu_chr_fe_deinit(&d->chrs[i], false);
+ }
}
static void mux_chr_update_read_handlers(Chardev *chr)
{
MuxChardev *d = MUX_CHARDEV(chr);
+ int i;
- /* Fix up the real driver with mux routines */
- qemu_chr_fe_set_handlers_full(&d->chr,
- mux_chr_can_read,
- mux_chr_read,
- mux_chr_event,
- NULL,
- chr,
- chr->gcontext, true, false);
+ for (i = 0; i < d->be_cnt; i++) {
+ /* Fix up the real driver with mux routines */
+ qemu_chr_fe_set_handlers_full(&d->chrs[i],
+ mux_chr_can_read,
+ mux_chr_read,
+ mux_chr_event,
+ NULL,
+ chr,
+ chr->gcontext, true, false);
+ }
}
void mux_set_focus(Chardev *chr, int focus)
@@ -305,7 +345,7 @@ void mux_set_focus(Chardev *chr, int focus)
MuxChardev *d = MUX_CHARDEV(chr);
assert(focus >= 0);
- assert(focus < d->mux_cnt);
+ assert(focus < d->fe_cnt);
if (d->focus != -1) {
mux_chr_send_event(d, d->focus, CHR_EVENT_MUX_OUT);
@@ -324,19 +364,49 @@ static void qemu_chr_open_mux(Chardev *chr,
ChardevMux *mux = backend->u.mux.data;
Chardev *drv;
MuxChardev *d = MUX_CHARDEV(chr);
-
- drv = qemu_chr_find(mux->chardev);
- if (drv == NULL) {
- error_setg(errp, "mux: base chardev %s not found", mux->chardev);
+ const char *offset, *chardevs;
+ int length, i;
+
+ if (d->fe_cnt > 1) {
+ error_setg(errp,
+ "multiplexed chardev '%s' is already used "
+ "for frontend multiplexing",
+ chr->label);
return;
}
+ chardevs = mux->chardev;
+ for (i = 0; i < MAX_MUX; i++) {
+ char *chardev;
+
+ offset = qemu_strchrnul(chardevs, ',');
+ length = offset - chardevs;
+ if (!length) {
+ break;
+ }
+ chardev = strndupa(chardevs, length);
+ chardevs += length + 1;
+ drv = qemu_chr_find(chardev);
+ if (drv == NULL) {
+ error_setg(errp, "mux: base chardev %s not found", chardev);
+ goto deinit_on_error;
+ }
+ qemu_chr_fe_init(&d->chrs[i], drv, errp);
+ d->be_cnt += 1;
+ }
d->focus = -1;
/* only default to opened state if we've realized the initial
* set of muxes
*/
*be_opened = muxes_opened;
- qemu_chr_fe_init(&d->chr, drv, errp);
+
+ return;
+
+deinit_on_error:
+ for (i = 0; i < d->be_cnt; i++) {
+ qemu_chr_fe_deinit(&d->chrs[i], false);
+ }
+ d->be_cnt = 0;
}
static void qemu_chr_parse_mux(QemuOpts *opts, ChardevBackend *backend,
diff --git a/chardev/char.c b/chardev/char.c
index ba847b6e9eff..2643c79e5749 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -333,7 +333,7 @@ static bool qemu_chr_is_busy(Chardev *s)
{
if (CHARDEV_IS_MUX(s)) {
MuxChardev *d = MUX_CHARDEV(s);
- return d->mux_cnt >= 0;
+ return d->fe_cnt >= 0;
} else {
return s->be != NULL;
}
diff --git a/chardev/chardev-internal.h b/chardev/chardev-internal.h
index 4e03af31476c..72c2e4da7552 100644
--- a/chardev/chardev-internal.h
+++ b/chardev/chardev-internal.h
@@ -35,10 +35,13 @@
struct MuxChardev {
Chardev parent;
+ /* Linked frontends */
CharBackend *backends[MAX_MUX];
- CharBackend chr;
+ /* Linked backends */
+ CharBackend chrs[MAX_MUX];
int focus;
- int mux_cnt;
+ int fe_cnt;
+ int be_cnt;
int term_got_escape;
int max_size;
/* Intermediate input buffer catches escape sequences even if the
--
2.34.1