On 31.07.23 01:48, Gavin Shan wrote:
Runs into core dump on arm64 and the backtrace extracted from the
core dump is shown as below. It's caused by accessing @kvm_state which
isn't initialized at that point due to commit 176d073029 ("hw/arm/virt:
Use machine_memory_devices_init()"), where the machine's memory region
is added ealier than before.
s/ealier/earlier/
main
qemu_init
configure_accelerators
qemu_opts_foreach
do_configure_accelerator
accel_init_machine
kvm_init
virt_kvm_type
virt_set_memmap
machine_memory_devices_init
memory_region_add_subregion
memory_region_add_subregion_common
memory_region_update_container_subregions
memory_region_transaction_begin
qemu_flush_coalesced_mmio_buffer
kvm_flush_coalesced_mmio_buffer
Fix it by initializing @kvm_state early. With this applied, no crash
is observed on arm64.
Interestingly, we register memory listeners in kvm_init() after setting
kvm_state, so in theory it should have worked fine.
But it's rather surprising that we see kvm_flush_coalesced_mmio_buffer()
call even though we didn't even setup a listener with
kvm_coalesce_mmio_region / kvm_uncoalesce_mmio_region.
Such a notifier-specific flush might have been better placed in the
MemoryListener->begin() call. But that needs more thought, as
qemu_flush_coalesced_mmio_buffer() is called from a couple of places.
Fixes: 176d073029 ("hw/arm/virt: Use machine_memory_devices_init()")
Signed-off-by: Gavin Shan <gs...@redhat.com>
---
accel/kvm/kvm-all.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
index 373d876c05..c825cba12f 100644
--- a/accel/kvm/kvm-all.c
+++ b/accel/kvm/kvm-all.c
@@ -2464,6 +2464,7 @@ static int kvm_init(MachineState *ms)
qemu_mutex_init(&kml_slots_lock);
s = KVM_STATE(ms->accelerator);
+ kvm_state = s;
/*
* On systems where the kernel can support different base page
@@ -2695,8 +2696,6 @@ static int kvm_init(MachineState *ms)
#endif
}
- kvm_state = s;
-
ret = kvm_arch_init(ms, s);
if (ret < 0) {
goto err;
As an alternative, we might simply do nothing in
kvm_flush_coalesced_mmio_buffer(), in case kvm_state is not setup yet.
We don't have any notifier registered in that case.
Thanks!
--
Cheers,
David / dhildenb
