Add the helper function cpr_get_fd_param, to use when preserving
a file descriptor that is opened externally and passed to QEMU.
cpr_get_fd_param returns a descriptor number either from a QEMU
command-line parameter, from a getfd command, or from CPR state.
When a descriptor is passed to new QEMU via SCM_RIGHTS, its number
changes. Hence, during CPR, the command-line parameter is ignored
in new QEMU, and over-ridden by the value found in CPR state.
Similarly, if the descriptor was originally specified by a getfd
command in old QEMU, the fd number is not known outside of QEMU,
and it changes when sent to new QEMU via SCM_RIGHTS. Hence the
user cannot send getfd to new QEMU, but when the user sends a
hotplug command that references the fd, cpr_get_fd_param finds
its value in CPR state.
Signed-off-by: Steve Sistare <steven.sist...@oracle.com>
---
include/migration/cpr.h | 2 ++
migration/cpr.c | 40 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 42 insertions(+)
diff --git a/include/migration/cpr.h b/include/migration/cpr.h
index c5c191d..23d0af4 100644
--- a/include/migration/cpr.h
+++ b/include/migration/cpr.h
@@ -33,6 +33,8 @@ struct QIOChannel *cpr_state_ioc(void);
bool cpr_needed_for_reuse(void *opaque);
void cpr_kvm_close(void);
+int cpr_get_fd_param(const char *name, const char *fdname, int index,
+ bool *reused, Error **errp);
void cpr_transfer_init(void);
QEMUFile *cpr_transfer_output(MigrationChannel *channel, Error **errp);
diff --git a/migration/cpr.c b/migration/cpr.c
index 351e12d..c903b24 100644
--- a/migration/cpr.c
+++ b/migration/cpr.c
@@ -14,6 +14,7 @@
#include "migration/qemu-file.h"
#include "migration/savevm.h"
#include "migration/vmstate.h"
+#include "monitor/monitor.h"
#include "system/kvm.h"
#include "system/runstate.h"
#include "trace.h"
@@ -274,3 +275,42 @@ void cpr_kvm_close(void)
kvm_close();
vfio_kvm_device_close();
}
+
+/*
+ * cpr_get_fd_param: find a descriptor and return its value.
+ *
+ * @name: CPR name for the descriptor
+ * @fdname: An integer-valued string, or a name passed to a getfd command
+ * @index: CPR index of the descriptor
+ * @reused: returns true if the fd is found in CPR state, else false.
+ * @errp: returned error message
+ *
+ * If CPR is not being performed, then use @fdname to find the fd.
+ * If CPR is being performed, then ignore @fdname, and look for @name
+ * and @index in CPR state.
+ *
+ * On success returns the fd value, else returns -1.
+ */
+int cpr_get_fd_param(const char *name, const char *fdname, int index,
+ bool *reused, Error **errp)
+{
+ ERRP_GUARD();
+ int fd;
+
+ if (cpr_is_incoming()) {
+ fd = cpr_find_fd(name, index);
+ if (fd < 0) {
+ error_setg(errp, "cannot find saved value for fd %s", fdname);
+ }
+ *reused = true;
+ } else {
+ fd = monitor_fd_param(monitor_cur(), fdname, errp);
+ if (fd >= 0) {
+ cpr_save_fd(name, index, fd);
+ } else {
+ error_prepend(errp, "Could not parse object fd %s:", fdname);
+ }
+ *reused = false;
+ }
+ return fd;
+}
--
1.8.3.1
