In some cases, for example MMIO read, QEMU has to wait for the remote to
complete a command before proceeding. An eventfd based mechanism is
added to synchronize QEMU & remote process.
Signed-off-by: John G Johnson <john.g.john...@oracle.com>
Signed-off-by: Jagannathan Raman <jag.ra...@oracle.com>
Signed-off-by: Elena Ufimtseva <elena.ufimts...@oracle.com>
---
v1 -> v2:
- Added timeout to synchronization functions
include/io/proxy-link.h | 8 ++++++++
io/proxy-link.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 50 insertions(+)
diff --git a/include/io/proxy-link.h b/include/io/proxy-link.h
index ee78cdd..b76c574 100644
--- a/include/io/proxy-link.h
+++ b/include/io/proxy-link.h
@@ -28,7 +28,9 @@
#include <stddef.h>
#include <stdint.h>
#include <glib.h>
+#include <unistd.h>
#include <pthread.h>
+#include <sys/eventfd.h>
#include "qemu/osdep.h"
#include "qom/object.h"
@@ -133,11 +135,17 @@ struct ProxyLinkState {
proxy_link_callback callback;
};
+#define GET_REMOTE_WAIT eventfd(0, 0)
+#define PUT_REMOTE_WAIT(wait) close(wait)
+#define PROXY_LINK_WAIT_DONE 1
+
ProxyLinkState *proxy_link_create(void);
void proxy_link_finalize(ProxyLinkState *s);
void proxy_proc_send(ProxyLinkState *s, ProcMsg *msg, ProcChannel *chan);
int proxy_proc_recv(ProxyLinkState *s, ProcMsg *msg, ProcChannel *chan);
+uint64_t wait_for_remote(int efd);
+void notify_proxy(int fd, uint64_t val);
void proxy_link_init_channel(ProxyLinkState *s, ProcChannel **chan, int fd);
void proxy_link_destroy_channel(ProcChannel *chan);
diff --git a/io/proxy-link.c b/io/proxy-link.c
index 5eb9718..381a38e 100644
--- a/io/proxy-link.c
+++ b/io/proxy-link.c
@@ -31,6 +31,8 @@
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
+#include <limits.h>
+#include <poll.h>
#include "qemu/module.h"
#include "io/proxy-link.h"
@@ -216,6 +218,46 @@ int proxy_proc_recv(ProxyLinkState *s, ProcMsg *msg,
ProcChannel *chan)
return rc;
}
+uint64_t wait_for_remote(int efd)
+{
+ struct pollfd pfd = { .fd = efd, .events = POLLIN };
+ uint64_t val;
+ int ret;
+
+ ret = poll(&pfd, 1, 1000);
+
+ switch (ret) {
+ case 0:
+ qemu_log_mask(LOG_REMOTE_DEBUG, "Error wait_for_remote: Timed out\n");
+ /* TODO: Kick-off error recovery */
+ return ULLONG_MAX;
+ case -1:
+ qemu_log_mask(LOG_REMOTE_DEBUG, "Poll error wait_for_remote: %s\n",
+ strerror(errno));
+ return ULLONG_MAX;
+ default:
+ if (read(efd, &val, sizeof(val)) == -1) {
+ qemu_log_mask(LOG_REMOTE_DEBUG, "Error wait_for_remote: %s\n",
+ strerror(errno));
+ return ULLONG_MAX;
+ }
+ }
+
+ val = (val == ULLONG_MAX) ? val : (val - 1);
+
+ return val;
+}
+
+void notify_proxy(int efd, uint64_t val)
+{
+ val = (val == ULLONG_MAX) ? val : (val + 1);
+
+ if (write(efd, &val, sizeof(val)) == -1) {
+ qemu_log_mask(LOG_REMOTE_DEBUG, "Error notify_proxy: %s\n",
+ strerror(errno));
+ }
+}
+
static gboolean proxy_link_handler_prepare(GSource *gsrc, gint *timeout)
{
g_assert(timeout);
--
1.8.3.1
