kvmtool: fix VM exit race attempting to pthread_kill an exited thread
lkvm currently suffers from a Segmentation Fault when exiting, which can
also lead to the console not being cleaned up correctly after a VM exits.
The issue is that (the misnamed) kvm_cpu__reboot function sends a
SIGKVMEXIT to each vcpu thread, which causes those vcpu threads to exit
once their main loops (kvm_cpu__start) detect that cpu->is_running is
now false. The lack of synchronisation in this exit path means that a
concurrent pause event (due to the br_write_lock in ioport__unregister)
ends up sending SIGKVMPAUSE to an exited thread, resulting in a SEGV.
This patch fixes the issue by moving kvm_cpu__reboot into kvm.c
(renaming it in the process) where it can hold the pause_lock mutex
across the reboot operation. This in turn makes it safe for the pause
code to check the is_running field of each CPU before attempting to
send a SIGKVMPAUSE signal.
Signed-off-by: Will Deacon <will.deacon@arm.com>
diff --git a/kvm-ipc.c b/kvm-ipc.c
index 857b0dc..1ef3c3e 100644
--- a/kvm-ipc.c
+++ b/kvm-ipc.c
@@ -341,7 +341,7 @@
if (WARN_ON(type != KVM_IPC_STOP || len))
return;
- kvm_cpu__reboot(kvm);
+ kvm__reboot(kvm);
}
/* Pause/resume the guest using SIGUSR2 */
