[Xen-devel] [PATCH 3/3] tools/xenconsoled: Log Xen boot messages at startup.

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

When xenconsoled starts, there will be log lines in the Xen console ring from
boot, even though VIRQ_CON_RING is not yet pending.

Add a force option to handle_hv_logs() which bypasses the event channel check,
allowing xenconsoled to drain the Xen boot messages when it starts, rather
than at the first subsequent time that VIRQ_CON_RING becomes set.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Ian Campbell <Ian.Campbell@xxxxxxxxxx>
CC: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
---
 tools/console/daemon/io.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index b1268fa..ac08b5b 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -907,15 +907,15 @@ static void handle_xs(void)
        free(vec);
 }
 
-static void handle_hv_logs(xc_evtchn *xce_handle)
+static void handle_hv_logs(xc_evtchn *xce_handle, bool force)
 {
        static char buffer[1024*16];
        char *bufptr = buffer;
        unsigned int size;
        static uint32_t index = 0;
-       evtchn_port_or_error_t port;
+       evtchn_port_or_error_t port = -1;
 
-       if ((port = xc_evtchn_pending(xce_handle)) == -1)
+       if (!force && ((port = xc_evtchn_pending(xce_handle)) == -1))
                return;
 
        do
@@ -938,7 +938,8 @@ static void handle_hv_logs(xc_evtchn *xce_handle)
                                       "%d (%s)", errno, strerror(errno));
        } while (size == sizeof(buffer));
 
-       (void)xc_evtchn_unmask(xce_handle, port);
+       if (port != -1)
+               (void)xc_evtchn_unmask(xce_handle, port);
 }
 
 static void handle_log_reload(void)
@@ -1024,6 +1025,8 @@ void handle_io(void)
                              "%d (%s)", errno, strerror(errno));
                        goto out;
                }
+               /* Log the boot dmesg even if VIRQ_CON_RING isn't pending. */
+               handle_hv_logs(xce_handle, true);
        }
 
        xcg_handle = xc_gnttab_open(NULL, 0);
@@ -1134,7 +1137,7 @@ void handle_io(void)
                                      errno, strerror(errno));
                                break;
                        } else if (fds[xce_pollfd_idx].revents & POLLIN)
-                               handle_hv_logs(xce_handle);
+                               handle_hv_logs(xce_handle, false);
 
                        xce_pollfd_idx = -1;
                }
-- 
1.7.10.4


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