diff options
| author | Christian Borntraeger <borntraeger@de.ibm.com> | 2016-09-19 13:39:42 +0200 |
|---|---|---|
| committer | Christian Borntraeger <borntraeger@de.ibm.com> | 2016-09-28 13:24:51 +0200 |
| commit | f9530c32420fff941b7bc8bb5d90310eecab5a96 (patch) | |
| tree | 71dfffe8cad14ba939ea04632e5e29fda4c2a2e0 | |
| parent | bfcec59a23f42dcac18a434bd48bd60d6fc0e563 (diff) | |
s390x/kvm: Fix potential deadlock in sigp handling
If two VCPUs exit at the same time and target each other
with a sigp, both could run into a deadlock as run_on_cpu
on CPU0 will free the BQL when starting the CPU1 target routine.
CPU1 will run its sigp initiater for CPU0 before handling
the run_on_cpu requests, thus resulting in a dead lock.
As all qemu SIGPs are slow path anway we can use a big sigp
lock and allow only one SIGP for the guest at a time. We will
return condition code 2 (BUSY) on contention to the guest.
Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
| -rw-r--r-- | target-s390x/kvm.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/target-s390x/kvm.c b/target-s390x/kvm.c index 4b847a3be4..a95d3da0f8 100644 --- a/target-s390x/kvm.c +++ b/target-s390x/kvm.c @@ -132,6 +132,8 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = { KVM_CAP_LAST_INFO }; +static QemuMutex qemu_sigp_mutex; + static int cap_sync_regs; static int cap_async_pf; static int cap_mem_op; @@ -287,6 +289,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s) } } + qemu_mutex_init(&qemu_sigp_mutex); + return 0; } @@ -1774,6 +1778,11 @@ static int handle_sigp(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1) status_reg = &env->regs[r1]; param = (r1 % 2) ? env->regs[r1] : env->regs[r1 + 1]; + if (qemu_mutex_trylock(&qemu_sigp_mutex)) { + ret = SIGP_CC_BUSY; + goto out; + } + switch (order) { case SIGP_SET_ARCH: ret = sigp_set_architecture(cpu, param, status_reg); @@ -1783,7 +1792,9 @@ static int handle_sigp(S390CPU *cpu, struct kvm_run *run, uint8_t ipa1) dst_cpu = s390_cpu_addr2state(env->regs[r3]); ret = handle_sigp_single_dst(dst_cpu, order, param, status_reg); } + qemu_mutex_unlock(&qemu_sigp_mutex); +out: trace_kvm_sigp_finished(order, CPU(cpu)->cpu_index, dst_cpu ? CPU(dst_cpu)->cpu_index : -1, ret); |