[libvirt] [PATCH 3/3] qemuDomainPMSuspendForDuration: check for QEMU_CAPS_WAKEUP_SUSPEND_SUPPORT

[Daniel Henrique Barboza]

If the current QEMU guest can't wake up from suspend properly,
avoid suspending the guest at all. This is done by checking the
QEMU_CAPS_WAKEUP_SUSPEND_SUPPORT cap.

The absence of the cap indicates that we're dealing with a QEMU
version older than 4.0 (which implements the required QMP API).
In this case, proceed as usual with the suspend logic since
we can't assume whether the guest has support or not.

This is the output of dompmsuspend in a guest that does not
have wake-up support declared in the query-current-machine:

$ sudo ./run tools/virsh dompmsuspend ub1810-noACPI3 mem
error: Domain ub1810-noACPI3 could not be suspended
error: this function is not supported by the connection driver: Domain does not have suspend support

Fixes: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/1759509
Reported-by: Balamuruhan S <bala24 at linux.vnet.ibm.com>
Signed-off-by: Daniel Henrique Barboza <danielhb413 at gmail.com>
---

I am not sure if Libvirt uses Launchpad for bug tracking like QEMU
does. If it's not the case, I believe the 'Fixes:' line up above can
be ignored/deleted.


 src/qemu/qemu_driver.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 62d8d977c5..9f1f170dfc 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -19209,6 +19209,8 @@ qemuDomainPMSuspendForDuration(virDomainPtr dom,
     virQEMUDriverPtr driver = dom->conn->privateData;
     virDomainObjPtr vm;
     qemuAgentPtr agent;
+    qemuDomainObjPrivatePtr priv;
+    bool hasQueryMachineAPI = false;
     int ret = -1;
 
     virCheckFlags(0, -1);
@@ -19231,6 +19233,28 @@ qemuDomainPMSuspendForDuration(virDomainPtr dom,
     if (!(vm = qemuDomObjFromDomain(dom)))
         goto cleanup;
 
+    priv = vm->privateData;
+
+    /*
+     * We can't check just for QEMU_CAPS_WAKEUP_SUSPEND_SUPPORT because,
+     * in case this cap is disabled, it is not possible to tell if the guest
+     * does not have wake-up from suspend support or if the current QEMU
+     * instance does not have the API.
+     *
+     * The case we want to handle here is when QEMU has the API and
+     * QEMU_CAPS_WAKEUP_SUSPEND_SUPPORT cap is disabled. Otherwise, do
+     * not interfere with the suspend process.
+     */
+    hasQueryMachineAPI = virQEMUCapsGet(priv->qemuCaps,
+                                        QEMU_CAPS_QUERY_CURRENT_MACHINE);
+    if (hasQueryMachineAPI &&
+        !virQEMUCapsGet(priv->qemuCaps, QEMU_CAPS_WAKEUP_SUSPEND_SUPPORT)) {
+
+        virReportError(VIR_ERR_NO_SUPPORT, "%s",
+                       _("Domain does not have suspend support"));
+        goto cleanup;
+    }
+
     if (virDomainPMSuspendForDurationEnsureACL(dom->conn, vm->def) < 0)
         goto cleanup;
 
-- 
2.20.1