On Mon, 27 May 2019 18:36:25 +0200 Markus Armbruster <armbru@redhat.com> wrote:
Igor Mammedov <imammedo@redhat.com> writes:
QEMU will crash when device-memory-region-size property is read if ms->device_memory wasn't initialized yet (ex: property being inspected during preconfig time).
Reproduced:
$ qemu-system-x86_64 -nodefaults -S -display none -preconfig -qmp stdio {"QMP": {"version": {"qemu": {"micro": 50, "minor": 0, "major": 4}, "package": "v4.0.0-828-ga7b21f6762"}, "capabilities": ["oob"]}} {"execute": "qmp_capabilities"} {"return": {}} {"execute": "qom-get", "arguments": {"path": "/machine", "property": "device-memory-region-size"}} Segmentation fault (core dumped)
First time I started looking at this series, I went "I'll need a reproducer to fully understand what's up, and I don't feel like finding one now; next series, please". Second time, I had to spend a few minutes on the reproducer. Wasn't hard, since you provided a clue. Still: make review easy, include a reproducer whenever you can.
sure
Instead of crashing return 0 if ms->device_memory hasn't been initialized.
Signed-off-by: Igor Mammedov <imammedo@redhat.com> --- hw/i386/pc.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/hw/i386/pc.c b/hw/i386/pc.c index d98b737..de91e90 100644 --- a/hw/i386/pc.c +++ b/hw/i386/pc.c @@ -2461,7 +2461,11 @@ pc_machine_get_device_memory_region_size(Object *obj, Visitor *v, Error **errp) { MachineState *ms = MACHINE(obj); - int64_t value = memory_region_size(&ms->device_memory->mr); + int64_t value = 0; + + if (ms->device_memory) { + memory_region_size(&ms->device_memory->mr); + }
visit_type_int(v, name, &value, errp); }
This makes qom-get return 0 for the size of memory that doesn't exist, yet.
A possible alternative would be setting an error.
Opinions?
We don't have a notion of property not set in QOM, so a code that will receive a text based error will have to parse it (horrible idea) to avoid generation of related ACPI parts. In case of not enabled memory hotplug, PC_MACHINE_DEVMEM_REGION_SIZE == 0 is valid value and it's what's expected by other code.