diff options
Diffstat (limited to 'arch/s390/kvm/sigp.c')
| -rw-r--r-- | arch/s390/kvm/sigp.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c index 683036c1c92a..3dc921e853b6 100644 --- a/arch/s390/kvm/sigp.c +++ b/arch/s390/kvm/sigp.c @@ -288,6 +288,34 @@ static int handle_sigp_dst(struct kvm_vcpu *vcpu, u8 order_code, if (!dst_vcpu) return SIGP_CC_NOT_OPERATIONAL; + /* + * SIGP RESTART, SIGP STOP, and SIGP STOP AND STORE STATUS orders + * are processed asynchronously. Until the affected VCPU finishes + * its work and calls back into KVM to clear the (RESTART or STOP) + * interrupt, we need to return any new non-reset orders "busy". + * + * This is important because a single VCPU could issue: + * 1) SIGP STOP $DESTINATION + * 2) SIGP SENSE $DESTINATION + * + * If the SIGP SENSE would not be rejected as "busy", it could + * return an incorrect answer as to whether the VCPU is STOPPED + * or OPERATING. + */ + if (order_code != SIGP_INITIAL_CPU_RESET && + order_code != SIGP_CPU_RESET) { + /* + * Lockless check. Both SIGP STOP and SIGP (RE)START + * properly synchronize everything while processing + * their orders, while the guest cannot observe a + * difference when issuing other orders from two + * different VCPUs. + */ + if (kvm_s390_is_stop_irq_pending(dst_vcpu) || + kvm_s390_is_restart_irq_pending(dst_vcpu)) + return SIGP_CC_BUSY; + } + switch (order_code) { case SIGP_SENSE: vcpu->stat.instruction_sigp_sense++; |