[libvirt] [PATCH] qemu: lifecycle: guest get rebooted after reboot and shutdown

[zhang bo]

Steps:
    1 virsh reboot guest1 --mode=acpi
    2 virsh shutdown guest1 --mode=agent

Expected result:
    As the SHUTDOWN job is after REBOOT, we expected the guest to be *shutoff*.

Exacted result:
    After the 2 steps above, the guest got *rebooted*.

The reason to this problem:
    1 in qemuDomainReboot(mode acpi), it sets priv->fakeReboot to 1.
    2 after shutdown/reboot, qemu monitor IO trigged qemuProcessHandleShutdown(), which finds that priv->fakeReboot is 1, and reboot the guest.

Root Cause of the problem:
    After further look into  the problem, We found that the design of acpi/agent shutdown/reboot seems a little chaotic.
    -----------------------------------
    sheet1 who sets fakeReboot
    -----------------------------------
             shutdown           reboot
    acpi        Y(0)              Y(1)
    agent       N                 N
    It's apparently, *acpi-mode* jobs set fakeReboot.
    -----------------------------------
    sheet2 who needs to check fakeReboot(qemuProcessHandleShutdown())
    -----------------------------------
             shutdown           reboot
    acpi        Y                 Y
    agent      *Y*               *N*
    Things become a little odd here. only agent-mode reboot doesn't check fakeReboot.

    We can tell from the above 2 sheets, that they're not consistent.
    *Agent-mode shutdown checks fakeReboot(trigger by SHUTDOWN monitorIO event), while it didn't set it before.*

    The chaos is not caused by libvirtd, it's a systematic problem, including guest os and qemu. (guest os writes ACPI, triggers qemu, qemu then triggers libvirtd)

Solution:
    A simple solution is to make the 1st sheet consistent to the 2nd sheet, which is:
    -----------------------------------
    sheet3 who should set fakeReboot:
    -----------------------------------
             shutdown           reboot
    acpi        Y(0)              Y(1)
    agent      *Y(0)*             N
    -----------------------------------
    we let agent-mode shutdown set fakeReboot to 0.

Signed-off-by: Zhang Bo <oscar.zhangbo at huawei.com>
Signed-off-by: Wang Yufei <james.wangyufei at huawei.com>
---
 src/qemu/qemu_driver.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 7eb5a7d..c751dcf 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -1959,6 +1959,8 @@ static int qemuDomainShutdownFlags(virDomainPtr dom, unsigned int flags)
         goto endjob;
     }

+    qemuDomainSetFakeReboot(driver, vm, isReboot);
+
     if (useAgent) {
         qemuDomainObjEnterAgent(vm);
         ret = qemuAgentShutdown(priv->agent, agentFlag);
@@ -1970,7 +1972,6 @@ static int qemuDomainShutdownFlags(virDomainPtr dom, unsigned int flags)
      */
     if (!useAgent ||
         (ret < 0 && (acpiRequested || !flags))) {
-        qemuDomainSetFakeReboot(driver, vm, isReboot);

         /* Even if agent failed, we have to check if guest went away
          * by itself while our locks were down.  */
-- 
1.7.12.4