kvm: Fix IRQ injection into full queue
User space may only inject interrupts during kvm_arch_pre_run if
ready_for_interrupt_injection is set in kvm_run. But that field is
updated on exit from KVM_RUN, so we must ensure that we enter the
kernel after potentially queuing an interrupt, otherwise we risk to
loose one - like it happens with the current code against latest
kernel modules (since kvm-86) that started to queue only a single
interrupt.
Fix the problem by reordering kvm_cpu_exec.
Credits go to Gleb Natapov for analyzing the issue in details.
(cherry picked from commit
8c14c17395809dfb2b20bd3598e067d2c5af7dc4)
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>