[libvirt] [PATCH v2 4/5] qemuDomainResumeFlags: Introduce VIR_DOMAIN_RESUME_SYNC_TIME

[Michal Privoznik]

This flag can be used to sync the domain's time right after
domain CPUs are started. It's basically backing call of two
subsequent APIs into one:

1) virDomainResume(dom)
2) virDomainSetTime(dom, 0, 0, VIR_DOMAIN_TIME_SYNC)

Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
---
 include/libvirt/libvirt-domain.h |  7 +++++++
 src/libvirt-domain.c             | 18 ++++++++++++------
 src/qemu/qemu_driver.c           | 20 +++++++++++++++++++-
 3 files changed, 38 insertions(+), 7 deletions(-)

diff --git a/include/libvirt/libvirt-domain.h b/include/libvirt/libvirt-domain.h
index 1795dd3..faafee4 100644
--- a/include/libvirt/libvirt-domain.h
+++ b/include/libvirt/libvirt-domain.h
@@ -867,6 +867,13 @@ int                     virDomainFree           (virDomainPtr domain);
 /*
  * Domain suspend/resume
  */
+typedef enum {
+    VIR_DOMAIN_RESUME_SYNC_TIME = 1 << 0,   /* On resume sync domain time from
+                                               its RTC. Depending on underlying
+                                               hypervisor it may require guest
+                                               agent. */
+} virDomainResumeFlagsValues;
+
 int                     virDomainSuspend        (virDomainPtr domain);
 int                     virDomainResume         (virDomainPtr domain);
 int                     virDomainResumeFlags    (virDomainPtr domain,
diff --git a/src/libvirt-domain.c b/src/libvirt-domain.c
index 7d21d77..7c8ccd8 100644
--- a/src/libvirt-domain.c
+++ b/src/libvirt-domain.c
@@ -695,13 +695,19 @@ virDomainResume(virDomainPtr domain)
 /**
  * virDomainResumeFlags:
  * @domain: a domain object
- * @flags: extra flags; not used yet, so callers should always pass 0
+ * @flags: bitwise-OR of virDomainResumeFlagsValues
  *
- * Resume a suspended domain, the process is restarted from the state where
- * it was frozen by calling virDomainSuspend().
- * This function may require privileged access
- * Moreover, resume may not be supported if domain is in some
- * special state like VIR_DOMAIN_PMSUSPENDED.
+ * Resume a suspended domain, the process is restarted from the
+ * state where it was frozen by calling virDomainSuspend().  This
+ * function may require privileged access Moreover, resume may
+ * not be supported if domain is in some special state like
+ * VIR_DOMAIN_PMSUSPENDED.  If VIR_DOMAIN_RESUME_SYNC_TIME flag
+ * is specified the domain's time is synced once its vCPUs are
+ * started. Depending on driver, this flag may require guest
+ * agent. However, due to nature of things in such drivers, vCPUs
+ * may have executed some instructions prior the time is set.
+ * Moreover, if time synchronisation fails, domain remains
+ * resumed, so you should check the domain state on error.
  *
  * Returns 0 in case of success and -1 in case of failure.
  */
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7065999..342d630 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1933,7 +1933,7 @@ qemuDomainResumeFlags(virDomainPtr dom,
     virQEMUDriverConfigPtr cfg = NULL;
     virCapsPtr caps = NULL;
 
-    virCheckFlags(0, -1);
+    virCheckFlags(VIR_DOMAIN_RESUME_SYNC_TIME, -1);
 
     if (!(vm = qemuDomObjFromDomain(dom)))
         return -1;
@@ -1974,6 +1974,24 @@ qemuDomainResumeFlags(virDomainPtr dom,
         goto endjob;
     if (virDomainSaveStatus(driver->xmlopt, cfg->stateDir, vm) < 0)
         goto endjob;
+
+    if (flags & VIR_DOMAIN_RESUME_SYNC_TIME) {
+        if (!virDomainObjIsActive(vm)) {
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           "%s", _("domain is not running"));
+            goto endjob;
+        }
+
+        if (qemuDomainSetTimeImpl(driver, vm, 0, 0, true) < 0) {
+            /* Intentionally overwrite the error, to make it
+             * obvious that guest is running. */
+            virReportError(VIR_ERR_OPERATION_FAILED, "%s",
+                           _("domain resumed, but time "
+                             "synchronization failed!"));
+            goto endjob;
+        }
+    }
+
     ret = 0;
 
  endjob:
-- 
2.0.4