From 199b5763d329b43c88f6ad539db8a6c6b42f8edb Mon Sep 17 00:00:00 2001 From: "Longpeng(Mike)" Date: Tue, 8 Aug 2017 12:05:32 +0800 Subject: KVM: add spinlock optimization framework If a vcpu exits due to request a user mode spinlock, then the spinlock-holder may be preempted in user mode or kernel mode. (Note that not all architectures trap spin loops in user mode, only AMD x86 and ARM/ARM64 currently do). But if a vcpu exits in kernel mode, then the holder must be preempted in kernel mode, so we should choose a vcpu in kernel mode as a more likely candidate for the lock holder. This introduces kvm_arch_vcpu_in_kernel() to decide whether the vcpu is in kernel-mode when it's preempted. kvm_vcpu_on_spin's new argument says the same of the spinning VCPU. Signed-off-by: Longpeng(Mike) Signed-off-by: Paolo Bonzini --- virt/kvm/arm/arm.c | 5 +++++ virt/kvm/kvm_main.c | 4 +++- 2 files changed, 8 insertions(+), 1 deletion(-) (limited to 'virt') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index a39a1e161e63..862f820d06d4 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -416,6 +416,11 @@ int kvm_arch_vcpu_runnable(struct kvm_vcpu *v) && !v->arch.power_off && !v->arch.pause); } +bool kvm_arch_vcpu_in_kernel(struct kvm_vcpu *vcpu) +{ + return false; +} + /* Just ensure a guest exit from a particular CPU */ static void exit_vm_noop(void *info) { diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 15252d723b54..e17c40d986f3 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -2317,7 +2317,7 @@ static bool kvm_vcpu_eligible_for_directed_yield(struct kvm_vcpu *vcpu) #endif } -void kvm_vcpu_on_spin(struct kvm_vcpu *me) +void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) { struct kvm *kvm = me->kvm; struct kvm_vcpu *vcpu; @@ -2348,6 +2348,8 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me) continue; if (swait_active(&vcpu->wq) && !kvm_arch_vcpu_runnable(vcpu)) continue; + if (yield_to_kernel_mode && !kvm_arch_vcpu_in_kernel(vcpu)) + continue; if (!kvm_vcpu_eligible_for_directed_yield(vcpu)) continue; -- cgit v1.2.3