diff options
| author | Christoffer Dall <christoffer.dall@linaro.org> | 2017-10-27 20:57:51 +0300 |
|---|---|---|
| committer | Christoffer Dall <christoffer.dall@linaro.org> | 2018-01-02 12:05:46 +0300 |
| commit | 61bbe38027334780964e4b2658f722ed0b3cb2f9 (patch) | |
| tree | 51acd9c382cbb311bf931a68552eeae3ae20e27f /virt/kvm/arm/arch_timer.c | |
| parent | 4c60e360d6dfa4d9c3586b687f348eeb3fd675dd (diff) | |
| download | linux-61bbe38027334780964e4b2658f722ed0b3cb2f9.tar.xz | |
KVM: arm/arm64: Avoid work when userspace iqchips are not used
We currently check if the VM has a userspace irqchip in several places
along the critical path, and if so, we do some work which is only
required for having an irqchip in userspace. This is unfortunate, as we
could avoid doing any work entirely, if we didn't have to support
irqchip in userspace.
Realizing the userspace irqchip on ARM is mostly a developer or hobby
feature, and is unlikely to be used in servers or other scenarios where
performance is a priority, we can use a refcounted static key to only
check the irqchip configuration when we have at least one VM that uses
an irqchip in userspace.
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Diffstat (limited to 'virt/kvm/arm/arch_timer.c')
| -rw-r--r-- | virt/kvm/arm/arch_timer.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index d845d67b7062..cfcd0323deab 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -103,7 +103,8 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id) if (kvm_timer_irq_can_fire(vtimer)) kvm_timer_update_irq(vcpu, true, vtimer); - if (unlikely(!irqchip_in_kernel(vcpu->kvm))) + if (static_branch_unlikely(&userspace_irqchip_in_use) && + unlikely(!irqchip_in_kernel(vcpu->kvm))) kvm_vtimer_update_mask_user(vcpu); return IRQ_HANDLED; @@ -284,7 +285,8 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_ctx->irq.irq, timer_ctx->irq.level); - if (likely(irqchip_in_kernel(vcpu->kvm))) { + if (!static_branch_unlikely(&userspace_irqchip_in_use) && + likely(irqchip_in_kernel(vcpu->kvm))) { ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id, timer_ctx->irq.irq, timer_ctx->irq.level, |