[Xen-devel] [RFC PATCH 11/17] xenconsoled: add support for consoles using 'state' xenstore entry

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Add support for standard xenbus initialization protocol using 'state'
xenstore entry. It will be necessary for secondary consoles.
For consoles supporting it, read 'state' entry on the frontend and
proceed accordingly - either init console or close it. When closing,
make sure all the in-transit data is flushed (both from shared ring and
from local buffer), if possible. This is especially important for
MiniOS-based qemu stubdomain, which closes console just after writing
device model state to it.
For consoles without 'state' field behavior is unchanged - on any watch
event try to connect console, as long as domain is alive.
---
 tools/console/daemon/io.c | 86 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 83 insertions(+), 3 deletions(-)

diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index 8aae87d..92c3dff 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -25,6 +25,7 @@
 #include <xengnttab.h>
 #include <xenstore.h>
 #include <xen/io/console.h>
+#include <xen/io/xenbus.h>
 #include <xen/grant_table.h>
 
 #include <stdlib.h>
@@ -109,6 +110,7 @@ struct console {
        struct domain *d;
        bool optional;
        bool use_gnttab;
+       bool have_state;
 };
 
 struct console_type {
@@ -117,6 +119,7 @@ struct console_type {
        char *log_suffix;
        bool optional;
        bool use_gnttab;
+       bool have_state;  // uses 'state' xenstore entry
 };
 
 static struct console_type console_type[] = {
@@ -156,6 +159,8 @@ typedef void (*VOID_ITER_FUNC_ARG2)(struct console *,  void 
*);
 typedef int (*INT_ITER_FUNC_ARG3)(struct console *,
                                  struct domain *dom, void **);
 
+static void handle_tty_write(struct console *con);
+
 static inline bool console_enabled(struct console *con)
 {
        return con->local_port != -1;
@@ -647,6 +652,20 @@ static int xs_gather(struct xs_handle *xs, const char 
*dir, ...)
        return ret;
 }
 
+static void set_backend_state(struct console *con, int state)
+{
+       char path[PATH_MAX], state_str[2], *be_path;
+
+       snprintf(state_str, sizeof(state_str), "%d", state);
+       snprintf(path, sizeof(path), "%s/backend", con->xspath);
+       be_path = xs_read(xs, XBT_NULL, path, NULL);
+       if (be_path) {
+               snprintf(path, sizeof(path), "%s/state", be_path);
+               xs_write(xs, XBT_NULL, path, state_str, 1);
+               free(be_path);
+       }
+}
+
 static void console_unmap_interface(struct console *con)
 {
        if (con->interface == NULL)
@@ -658,7 +677,7 @@ static void console_unmap_interface(struct console *con)
        con->interface = NULL;
        con->ring_ref = -1;
 }
- 
+
 static int console_create_ring(struct console *con)
 {
        int err, remote_port, ring_ref, rc;
@@ -762,10 +781,70 @@ static int console_create_ring(struct console *con)
        if (log_guest && (con->log_fd == -1))
                con->log_fd = create_console_log(con);
 
+       /* if everything ok, signal backend readiness, in backend tree */
+       set_backend_state(con, XenbusStateConnected);
+
  out:
        return err;
 }
 
+/* gracefully close console */
+static int console_close(struct console *con) {
+
+       if (con->interface && con->master_fd != -1 && con->buffer.data) {
+               /* handle remaining data in buffers */
+               buffer_append(con);
+
+               /* write it out, if possible */
+               if (con->master_pollfd_idx != -1) {
+                       if (fds[con->master_pollfd_idx].revents &
+                                       POLLOUT)
+                               handle_tty_write(con);
+               }
+       }
+
+       console_close_tty(con);
+       console_unmap_interface(con);
+       set_backend_state(con, XenbusStateClosed);
+
+       return 0;
+}
+
+
+static int handle_console_state(struct console *con) {
+       int err, state;
+
+       if (!con->have_state)
+               return console_create_ring(con);
+
+       err = xs_gather(xs, con->xspath,
+                       "state", "%u", &state,
+                       NULL);
+       if (err)
+               /* no 'state' entry, assume removal */
+               state = XenbusStateClosed;
+
+       switch (state) {
+               case XenbusStateInitialising:
+               case XenbusStateInitWait:
+                       /* wait for frontent init */
+                       return 0;
+               case XenbusStateInitialised:
+               case XenbusStateConnected:
+                       /* ok, init backend (also on restart) */
+                       return console_create_ring(con);
+               case XenbusStateClosing:
+               case XenbusStateClosed:
+                       /* close requested */
+                       return console_close(con);
+               default:
+                       dolog(LOG_ERR,
+                             "Invalid state %d set by console %s of domain 
%d\n",
+                             state, con->xspath, con->d->domid);
+                       return 1;
+       }
+}
+
 static int watch_domain(struct console *con, struct domain *dom, void **data)
 {
        bool watch = data;
@@ -776,7 +855,7 @@ static int watch_domain(struct console *con, struct domain 
*dom, void **data)
        if (watch) {
                success = xs_watch(xs, con->xspath, domid_str);
                if (success)
-                       console_create_ring(con);
+                       handle_console_state(con);
                else
                        xs_unwatch(xs, con->xspath, domid_str);
        } else {
@@ -814,6 +893,7 @@ static int console_init(struct console *con, struct domain 
*dom, void **data)
        con->log_suffix = (*con_type)->log_suffix;
        con->optional = (*con_type)->optional;
        con->use_gnttab = (*con_type)->use_gnttab;
+       con->have_state = (*con_type)->have_state;
        xsname = (char *)(*con_type)->xsname;
        xspath = xs_get_domain_path(xs, dom->domid);
        s = realloc(xspath, strlen(xspath) +
@@ -1124,7 +1204,7 @@ static void handle_xs(void)
                /* We may get watches firing for domains that have recently
                   been removed, so dom may be NULL here. */
                if (dom && dom->is_dead == false)
-                       console_iter_int_arg1(dom, console_create_ring);
+                       console_iter_int_arg1(dom, handle_console_state);
        }
 
        free(vec);
-- 
git-series 0.9.1

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