We can interrupt the vcpu only when it's running in guest mode to reduce IPI
It looks like only ia64 and x86 need to send IPI to other vcpus, so i only add the implementation of 'vcpu->guest_mode' in ia64, but i don't know ia64 well, please point out the right way for me if the implementation is incorrect Also reorganize struct kvm_vcpu to make ->guest_mode and ->requests in the same cache line explicitly. Signed-off-by: Xiao Guangrong <[email protected]> --- arch/ia64/kvm/kvm-ia64.c | 2 ++ arch/x86/kvm/x86.c | 6 +++++- include/linux/kvm_host.h | 9 +++++---- virt/kvm/kvm_main.c | 7 ++++++- 4 files changed, 18 insertions(+), 6 deletions(-) diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c index 70d224d..15c11b2 100644 --- a/arch/ia64/kvm/kvm-ia64.c +++ b/arch/ia64/kvm/kvm-ia64.c @@ -662,6 +662,7 @@ again: goto vcpu_run_fail; srcu_read_unlock(&vcpu->kvm->srcu, idx); + atomic_set(&vcpu->guest_mode, 1); kvm_guest_enter(); /* @@ -683,6 +684,7 @@ again: */ barrier(); kvm_guest_exit(); + atomic_set(&vcpu->guest_mode, 0); preempt_enable(); idx = srcu_read_lock(&vcpu->kvm->srcu); diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 0b77e9c..f882158 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -5214,7 +5214,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) kvm_load_guest_xcr0(vcpu); atomic_set(&vcpu->guest_mode, 1); - smp_wmb(); + + /* We should set ->guest_mode before check ->requests, + * see the comment in make_all_cpus_request. + */ + smp_mb(); local_irq_disable(); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index b5021db..5f5ef74 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -103,14 +103,15 @@ struct kvm_vcpu { #ifdef CONFIG_PREEMPT_NOTIFIERS struct preempt_notifier preempt_notifier; #endif + int cpu; int vcpu_id; - struct mutex mutex; - int cpu; + int srcu_idx; atomic_t guest_mode; - struct kvm_run *run; unsigned long requests; unsigned long guest_debug; - int srcu_idx; + + struct mutex mutex; + struct kvm_run *run; int fpu_active; int guest_fpu_loaded, guest_xcr0_loaded; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index b1b6cbb..a475264 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -153,7 +153,12 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req) if (kvm_make_check_request(req, vcpu)) continue; cpu = vcpu->cpu; - if (cpus != NULL && cpu != -1 && cpu != me) + + /* Set ->requests bit before we read ->guest_mode */ + smp_mb(); + + if (cpus != NULL && cpu != -1 && cpu != me && + atomic_read(&vcpu->guest_mode)) cpumask_set_cpu(cpu, cpus); } if (unlikely(cpus == NULL)) -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
