With the addition of the spinning waiting for the exit event to be
received in the CMOS device a regression was introduced into the CMOS
fuzzer. Since there is nothing to receive the event in the fuzzer and
there is nothing to update the bit the that the device is looping on;
introducing an infinite loop.
Use an Option<> type so that when running the device in the fuzzer no
Arc<AtomicBool> is provided effectively disabling the spinning logic.
Fixes: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=61165
Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
The reset system is asynchronous with an I/O event (PIO or MMIO) for
ACPI/i8042/CMOS triggering a write to the reset_evt event handler. The
VMM thread will pick up this event on the VMM main loop and then trigger
a shutdown in the CpuManager. However since there is some delay between
the CPU threads being marked to be killed (through the
CpuManager::cpus_kill_signalled bool) it is possible for the guest vCPU
that triggered the exit to be re-entered when the vCPU KVM_RUN is called
after the I/O exit is completed.
This is undesirable and in particular the Linux kernel will attempt to
jump to real mode after a CMOS based exit - this is unsupported in
nested KVM on AMD on Azure and will trigger an error in KVM_RUN.
Solve this problem by spinning in the device that has triggered the
reset until the vcpus_kill_signalled boolean has been updated
indicating that the VMM thread has received the event and called
CpuManager::shutdown(). In particular if this bool is set then the vCPU
threads will not re-enter the guest.
Signed-off-by: Rob Bradford <rbradford@rivosinc.com>
