qemu-e2k/hw
David Hildenbrand 9bc9d3d1ae s390x/tod: Properly stop the KVM TOD while the guest is not running
Just like on other architectures, we should stop the clock while the guest
is not running. This is already properly done for TCG. Right now, doing an
offline migration (stop, migrate, cont) can easily trigger stalls in the
guest.

Even doing a
    (hmp) stop
    ... wait 2 minutes ...
    (hmp) cont
will already trigger stalls.

So whenever the guest stops, backup the KVM TOD. When continuing to run
the guest, restore the KVM TOD.

One special case is starting a simple VM: Reading the TOD from KVM to
stop it right away until the guest is actually started means that the
time of any simple VM will already differ to the host time. We can
simply leave the TOD running and the guest won't be able to recognize
it.

For migration, we actually want to keep the TOD stopped until really
starting the guest. To be able to catch most errors, we should however
try to set the TOD in addition to simply storing it. So we can still
catch basic migration problems.

If anything goes wrong while backing up/restoring the TOD, we have to
ignore it (but print a warning). This is then basically a fallback to
old behavior (TOD remains running).

I tested this very basically with an initrd:
    1. Start a simple VM. Observed that the TOD is kept running. Old
       behavior.
    2. Ordinary live migration. Observed that the TOD is temporarily
       stopped on the destination when setting the new value and
       correctly started when finally starting the guest.
    3. Offline live migration. (stop, migrate, cont). Observed that the
       TOD will be stopped on the source with the "stop" command. On the
       destination, the TOD is temporarily stopped when setting the new
       value and correctly started when finally starting the guest via
       "cont".
    4. Simple stop/cont correctly stops/starts the TOD. (multiple stops
       or conts in a row have no effect, so works as expected)

In the future, we might want to send the guest a special kind of time sync
interrupt under some conditions, so it can synchronize its tod to the
host tod. This is interesting for migration scenarios but also when we
get time sync interrupts ourselves. This however will most probably have
to be handled in KVM (e.g. when the tods differ too much) and is not
desired e.g. when debugging the guest (single stepping should not
result in permanent time syncs). I consider something like that an add-on
on top of this basic "don't break the guest" handling.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20181130094957.4121-1-david@redhat.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
2018-12-12 10:39:28 +01:00
..
9pfs 9p: fix QEMU crash when renaming files 2018-11-23 13:28:03 +01:00
acpi hw/acpi/nvdimm: Don't take address of fields in packed structs 2018-11-12 15:14:06 +00:00
adc Include qapi/error.h exactly where needed 2018-02-09 13:50:17 +01:00
alpha hw/alpha/typhoon: Remove unuseful code 2018-10-24 06:44:59 -03:00
arm virt: Eliminate separate instance_init functions 2018-12-11 15:45:22 -02:00
audio audio/hda: fix guest triggerable assert 2018-11-27 07:47:57 +01:00
block nvme: Fix spurious interrupts 2018-11-27 12:59:00 +01:00
bt hw/bt: Replace fprintf(stderr, "*\n" with error_report() 2018-01-22 09:51:00 +01:00
char hw/arm/stm32f205: Fix the UART and Timer region size 2018-11-19 15:29:08 +00:00
core qom: remove unimplemented class_finalize 2018-12-11 15:45:23 -02:00
cpu hw/cpu/a15mpcore: If CPU has EL2, enable it on the GIC and wire it up 2018-08-24 13:17:34 +01:00
cris hw/cris: Use the IEC binary prefix definitions 2018-07-02 15:41:15 +02:00
display vmstate: constify VMStateField 2018-11-27 15:35:15 +01:00
dma hw/dma/pl080: Remove hw_error() if DMA is enabled 2018-08-20 11:24:33 +01:00
gpio hw/i2c: Use DeviceClass::realize instead of I2CSlaveClass::init 2018-06-01 15:14:31 +02:00
hppa hw/hppa/dino: Remove unuseful code 2018-10-24 06:44:59 -03:00
hyperv hw/hyperv: fix NULL dereference with pure-kvm SynIC 2018-11-26 14:14:38 -02:00
i2c i2c: pm_smbus: check smb_index before block transfer write 2018-12-06 15:51:57 +00:00
i386 pc: Use default_machine_opts to set suppress_vmdesc 2018-12-11 15:45:22 -02:00
ide replay: replay BH for IDE trim operation 2018-10-02 19:09:13 +02:00
input ps2kbd: default to scan enabled after reset 2018-11-27 07:47:50 +01:00
intc vmstate: constify VMStateField 2018-11-27 15:35:15 +01:00
ipack hw/ipack: Use the IEC binary prefix definitions 2018-07-02 15:41:12 +02:00
ipmi ipmi: Use proper struct reference for BT vmstate 2018-08-23 18:46:25 +02:00
isa configs: Add a CONFIG_SMC37C669 switch for the "smc37c669-superio" device 2018-10-24 07:33:44 +01:00
lm32 milkymist: Check for failure trying to load BIOS image 2018-11-06 11:32:14 +00:00
m68k hw/m68k: Use the IEC binary prefix definitions 2018-07-02 15:41:14 +02:00
mem memory-device: avoid overflows on very huge devices 2018-12-11 15:45:22 -02:00
microblaze hw/microblaze/xlnx-zynqmp-pmu: Fix introspection problem in 'xlnx, zynqmp-pmu-soc' 2018-07-23 15:21:25 +01:00
mips hw/mips/malta: Remove unuseful code 2018-10-24 06:44:59 -03:00
misc qom: make user_creatable_complete() specific to UserCreatable 2018-12-11 15:45:22 -02:00
moxie change get_image_size return type to int64_t 2018-10-02 19:08:49 +02:00
net net: cadence_gem: Remove incorrect assert() 2018-11-26 13:41:42 +00:00
nios2 hw/nios2: Use the IEC binary prefix definitions 2018-07-02 15:41:15 +02:00
nvram vmstate: constify VMStateField 2018-11-27 15:35:15 +01:00
openrisc Change references to serial_hds[] to serial_hd() 2018-04-26 13:57:00 +01:00
pci vmstate: constify VMStateField 2018-11-27 15:35:15 +01:00
pci-bridge hw/pci-bridge/ioh3420: Remove unuseful header 2018-11-05 13:24:02 -05:00
pci-host ppc patch queue 2018-11-08 2018-11-08 14:42:37 +00:00
pcmcia hw: Clean up includes 2016-01-29 15:07:25 +00:00
ppc spapr: Delete instance_options functions 2018-12-11 15:45:22 -02:00
rdma config: split PVRDMA from RDMA 2018-08-18 18:01:34 +03:00
riscv hw/riscv/virt: Free the test device tree node name 2018-11-13 15:12:13 -08:00
s390x s390x/tod: Properly stop the KVM TOD while the guest is not running 2018-12-12 10:39:28 +01:00
scsi vmstate: constify VMStateField 2018-11-27 15:35:15 +01:00
sd ssi-sd: Make devices picking up backends unavailable with -device 2018-10-24 07:50:16 +01:00
sh4 hw/sh4/sh_pci: Use DeviceState::realize rather than SysBusDevice::init 2018-10-24 06:44:59 -03:00
smbios smbios: Clean up error handling in smbios_add() 2018-10-19 14:51:34 +02:00
sparc sun4m: don't use legacy fw_cfg_init_mem() function 2018-08-20 19:18:31 +01:00
sparc64 hw/sparc64/niagara: Model the I/O Bridge with the 'unimplemented_device' 2018-10-24 06:44:59 -03:00
ssi hw/ssi/xilinx_spi: Use DeviceState::realize rather than SysBusDevice::init 2018-10-24 06:44:59 -03:00
timer hw/timer/sun4v-rtc: Fix tracing at sun4v_rtc_write() 2018-12-11 15:45:22 -02:00
tpm tpm: use loop iterator to set sts data field 2018-11-14 15:47:24 -05:00
tricore hw/tricore: Use the IEC binary prefix definitions 2018-07-02 15:41:14 +02:00
unicore32 hw/input/i8042: Extract declarations from i386/pc.h into input/i8042.h 2018-03-12 16:12:48 +01:00
usb usb: mtp fixes. 2018-12-03 19:57:59 +00:00
vfio s390x/vfio-ap: report correct error 2018-11-05 09:55:01 +01:00
virtio qom: make user_creatable_complete() specific to UserCreatable 2018-12-11 15:45:22 -02:00
watchdog qapi: Drop qapi_event_send_FOO()'s Error ** argument 2018-08-28 18:21:38 +02:00
xen xen: Use the PCI_DEVICE macro 2018-10-26 17:17:32 +02:00
xenpv hw/xen: Use the IEC binary prefix definitions 2018-07-02 15:41:13 +02:00
xtensa target/xtensa: xtfpga: provide default memory sizes 2018-11-21 10:53:21 -08:00
Makefile.objs memory-device: introduce separate config option 2018-10-24 06:44:59 -03:00