| Message ID | 20171220113606.7030-9-christoffer.dall@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, 20 Dec 2017 11:36:05 +0000, Christoffer Dall wrote: > > 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. > > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> > --- > arch/arm/include/asm/kvm_host.h | 2 ++ > arch/arm64/include/asm/kvm_host.h | 2 ++ > virt/kvm/arm/arch_timer.c | 6 ++-- > virt/kvm/arm/arm.c | 59 ++++++++++++++++++++++++++++----------- > 4 files changed, 50 insertions(+), 19 deletions(-) > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h > index a9f7d3f47134..6394fb99da7f 100644 > --- a/arch/arm/include/asm/kvm_host.h > +++ b/arch/arm/include/asm/kvm_host.h > @@ -48,6 +48,8 @@ > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) > > +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > + > u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode); > int __attribute_const__ kvm_target_cpu(void); > int kvm_reset_vcpu(struct kvm_vcpu *vcpu); > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index ea6cb5b24258..e7218cf7df2a 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -47,6 +47,8 @@ > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) > > +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > + > int __attribute_const__ kvm_target_cpu(void); > int kvm_reset_vcpu(struct kvm_vcpu *vcpu); > int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext); > 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, > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > index 3610e132df8b..0cf0459134ff 100644 > --- a/virt/kvm/arm/arm.c > +++ b/virt/kvm/arm/arm.c > @@ -74,6 +74,8 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu) > __this_cpu_write(kvm_arm_running_vcpu, vcpu); > } > > +DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > + > /** > * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU. > * Must be called from non-preemptible context > @@ -302,6 +304,8 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu) > > void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) > { > + if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm))) > + static_branch_dec(&userspace_irqchip_in_use); > kvm_arch_vcpu_free(vcpu); > } > > @@ -522,14 +526,22 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) > > vcpu->arch.has_run_once = true; > > - /* > - * Map the VGIC hardware resources before running a vcpu the first > - * time on this VM. > - */ > - if (unlikely(irqchip_in_kernel(kvm) && !vgic_ready(kvm))) { > - ret = kvm_vgic_map_resources(kvm); > - if (ret) > - return ret; > + if (likely(irqchip_in_kernel(kvm))) { > + /* > + * Map the VGIC hardware resources before running a vcpu the > + * first time on this VM. > + */ > + if (unlikely(!vgic_ready(kvm))) { > + ret = kvm_vgic_map_resources(kvm); > + if (ret) > + return ret; > + } > + } else { > + /* > + * Tell the rest of the code that there are userspace irqchip > + * VMs in the wild. > + */ > + static_branch_inc(&userspace_irqchip_in_use); > } > > ret = kvm_timer_enable(vcpu); > @@ -664,18 +676,29 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > kvm_vgic_flush_hwstate(vcpu); > > /* > - * If we have a singal pending, or need to notify a userspace > - * irqchip about timer or PMU level changes, then we exit (and > - * update the timer level state in kvm_timer_update_run > - * below). > + * Exit if we have a singal pending so that we can deliver the nit: s/singal/signal/ > + * signal to user space. > */ > - if (signal_pending(current) || > - kvm_timer_should_notify_user(vcpu) || > - kvm_pmu_should_notify_user(vcpu)) { > + if (signal_pending(current)) { > ret = -EINTR; > run->exit_reason = KVM_EXIT_INTR; > } > > + /* > + * If we're using a userspace irqchip, then check if we need > + * to tell a userspace irqchip about timer or PMU level > + * changes and if so, exit to userspace (the actual level > + * state gets updated in kvm_timer_update_run and > + * kvm_pmu_update_run below. nit: missing closing parenthesis. > + */ > + if (static_branch_unlikely(&userspace_irqchip_in_use)) { > + if (kvm_timer_should_notify_user(vcpu) || > + kvm_pmu_should_notify_user(vcpu)) { > + ret = -EINTR; > + run->exit_reason = KVM_EXIT_INTR; > + } > + } > + > /* > * Ensure we set mode to IN_GUEST_MODE after we disable > * interrupts and before the final VCPU requests check. > @@ -688,7 +711,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > kvm_request_pending(vcpu)) { > vcpu->mode = OUTSIDE_GUEST_MODE; > kvm_pmu_sync_hwstate(vcpu); > - kvm_timer_sync_hwstate(vcpu); > + if (static_branch_unlikely(&userspace_irqchip_in_use)) > + kvm_timer_sync_hwstate(vcpu); > kvm_vgic_sync_hwstate(vcpu); > local_irq_enable(); > preempt_enable(); > @@ -732,7 +756,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > * we don't want vtimer interrupts to race with syncing the > * timer virtual interrupt state. > */ > - kvm_timer_sync_hwstate(vcpu); > + if (static_branch_unlikely(&userspace_irqchip_in_use)) > + kvm_timer_sync_hwstate(vcpu); > > /* > * We may have taken a host interrupt in HYP mode (ie > -- > 2.14.2 > Other than the trivial nits above: Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> M.
On Wed, Dec 27, 2017 at 04:36:04PM +0000, Marc Zyngier wrote: > On Wed, 20 Dec 2017 11:36:05 +0000, > Christoffer Dall wrote: > > > > 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. > > > > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> > > --- > > arch/arm/include/asm/kvm_host.h | 2 ++ > > arch/arm64/include/asm/kvm_host.h | 2 ++ > > virt/kvm/arm/arch_timer.c | 6 ++-- > > virt/kvm/arm/arm.c | 59 ++++++++++++++++++++++++++++----------- > > 4 files changed, 50 insertions(+), 19 deletions(-) > > > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h > > index a9f7d3f47134..6394fb99da7f 100644 > > --- a/arch/arm/include/asm/kvm_host.h > > +++ b/arch/arm/include/asm/kvm_host.h > > @@ -48,6 +48,8 @@ > > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) > > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) > > > > +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > > + > > u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode); > > int __attribute_const__ kvm_target_cpu(void); > > int kvm_reset_vcpu(struct kvm_vcpu *vcpu); > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > > index ea6cb5b24258..e7218cf7df2a 100644 > > --- a/arch/arm64/include/asm/kvm_host.h > > +++ b/arch/arm64/include/asm/kvm_host.h > > @@ -47,6 +47,8 @@ > > KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) > > #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) > > > > +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > > + > > int __attribute_const__ kvm_target_cpu(void); > > int kvm_reset_vcpu(struct kvm_vcpu *vcpu); > > int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext); > > 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, > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c > > index 3610e132df8b..0cf0459134ff 100644 > > --- a/virt/kvm/arm/arm.c > > +++ b/virt/kvm/arm/arm.c > > @@ -74,6 +74,8 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu) > > __this_cpu_write(kvm_arm_running_vcpu, vcpu); > > } > > > > +DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use); > > + > > /** > > * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU. > > * Must be called from non-preemptible context > > @@ -302,6 +304,8 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu) > > > > void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) > > { > > + if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm))) > > + static_branch_dec(&userspace_irqchip_in_use); > > kvm_arch_vcpu_free(vcpu); > > } > > > > @@ -522,14 +526,22 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) > > > > vcpu->arch.has_run_once = true; > > > > - /* > > - * Map the VGIC hardware resources before running a vcpu the first > > - * time on this VM. > > - */ > > - if (unlikely(irqchip_in_kernel(kvm) && !vgic_ready(kvm))) { > > - ret = kvm_vgic_map_resources(kvm); > > - if (ret) > > - return ret; > > + if (likely(irqchip_in_kernel(kvm))) { > > + /* > > + * Map the VGIC hardware resources before running a vcpu the > > + * first time on this VM. > > + */ > > + if (unlikely(!vgic_ready(kvm))) { > > + ret = kvm_vgic_map_resources(kvm); > > + if (ret) > > + return ret; > > + } > > + } else { > > + /* > > + * Tell the rest of the code that there are userspace irqchip > > + * VMs in the wild. > > + */ > > + static_branch_inc(&userspace_irqchip_in_use); > > } > > > > ret = kvm_timer_enable(vcpu); > > @@ -664,18 +676,29 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > > kvm_vgic_flush_hwstate(vcpu); > > > > /* > > - * If we have a singal pending, or need to notify a userspace > > - * irqchip about timer or PMU level changes, then we exit (and > > - * update the timer level state in kvm_timer_update_run > > - * below). > > + * Exit if we have a singal pending so that we can deliver the > > nit: s/singal/signal/ > dang, one more. > > + * signal to user space. > > */ > > - if (signal_pending(current) || > > - kvm_timer_should_notify_user(vcpu) || > > - kvm_pmu_should_notify_user(vcpu)) { > > + if (signal_pending(current)) { > > ret = -EINTR; > > run->exit_reason = KVM_EXIT_INTR; > > } > > > > + /* > > + * If we're using a userspace irqchip, then check if we need > > + * to tell a userspace irqchip about timer or PMU level > > + * changes and if so, exit to userspace (the actual level > > + * state gets updated in kvm_timer_update_run and > > + * kvm_pmu_update_run below. > > nit: missing closing parenthesis. > > > + */ > > + if (static_branch_unlikely(&userspace_irqchip_in_use)) { > > + if (kvm_timer_should_notify_user(vcpu) || > > + kvm_pmu_should_notify_user(vcpu)) { > > + ret = -EINTR; > > + run->exit_reason = KVM_EXIT_INTR; > > + } > > + } > > + > > /* > > * Ensure we set mode to IN_GUEST_MODE after we disable > > * interrupts and before the final VCPU requests check. > > @@ -688,7 +711,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > > kvm_request_pending(vcpu)) { > > vcpu->mode = OUTSIDE_GUEST_MODE; > > kvm_pmu_sync_hwstate(vcpu); > > - kvm_timer_sync_hwstate(vcpu); > > + if (static_branch_unlikely(&userspace_irqchip_in_use)) > > + kvm_timer_sync_hwstate(vcpu); > > kvm_vgic_sync_hwstate(vcpu); > > local_irq_enable(); > > preempt_enable(); > > @@ -732,7 +756,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) > > * we don't want vtimer interrupts to race with syncing the > > * timer virtual interrupt state. > > */ > > - kvm_timer_sync_hwstate(vcpu); > > + if (static_branch_unlikely(&userspace_irqchip_in_use)) > > + kvm_timer_sync_hwstate(vcpu); > > > > /* > > * We may have taken a host interrupt in HYP mode (ie > > -- > > 2.14.2 > > > > Other than the trivial nits above: > > Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> > Thanks for this. I've now queued this series and pushed it to kvmarm/next. -Christoffer
diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h index a9f7d3f47134..6394fb99da7f 100644 --- a/arch/arm/include/asm/kvm_host.h +++ b/arch/arm/include/asm/kvm_host.h @@ -48,6 +48,8 @@ KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); + u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode); int __attribute_const__ kvm_target_cpu(void); int kvm_reset_vcpu(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index ea6cb5b24258..e7218cf7df2a 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -47,6 +47,8 @@ KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1) +DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use); + int __attribute_const__ kvm_target_cpu(void); int kvm_reset_vcpu(struct kvm_vcpu *vcpu); int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext); 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, diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 3610e132df8b..0cf0459134ff 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -74,6 +74,8 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu) __this_cpu_write(kvm_arm_running_vcpu, vcpu); } +DEFINE_STATIC_KEY_FALSE(userspace_irqchip_in_use); + /** * kvm_arm_get_running_vcpu - get the vcpu running on the current CPU. * Must be called from non-preemptible context @@ -302,6 +304,8 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu) void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu) { + if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm))) + static_branch_dec(&userspace_irqchip_in_use); kvm_arch_vcpu_free(vcpu); } @@ -522,14 +526,22 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) vcpu->arch.has_run_once = true; - /* - * Map the VGIC hardware resources before running a vcpu the first - * time on this VM. - */ - if (unlikely(irqchip_in_kernel(kvm) && !vgic_ready(kvm))) { - ret = kvm_vgic_map_resources(kvm); - if (ret) - return ret; + if (likely(irqchip_in_kernel(kvm))) { + /* + * Map the VGIC hardware resources before running a vcpu the + * first time on this VM. + */ + if (unlikely(!vgic_ready(kvm))) { + ret = kvm_vgic_map_resources(kvm); + if (ret) + return ret; + } + } else { + /* + * Tell the rest of the code that there are userspace irqchip + * VMs in the wild. + */ + static_branch_inc(&userspace_irqchip_in_use); } ret = kvm_timer_enable(vcpu); @@ -664,18 +676,29 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) kvm_vgic_flush_hwstate(vcpu); /* - * If we have a singal pending, or need to notify a userspace - * irqchip about timer or PMU level changes, then we exit (and - * update the timer level state in kvm_timer_update_run - * below). + * Exit if we have a singal pending so that we can deliver the + * signal to user space. */ - if (signal_pending(current) || - kvm_timer_should_notify_user(vcpu) || - kvm_pmu_should_notify_user(vcpu)) { + if (signal_pending(current)) { ret = -EINTR; run->exit_reason = KVM_EXIT_INTR; } + /* + * If we're using a userspace irqchip, then check if we need + * to tell a userspace irqchip about timer or PMU level + * changes and if so, exit to userspace (the actual level + * state gets updated in kvm_timer_update_run and + * kvm_pmu_update_run below. + */ + if (static_branch_unlikely(&userspace_irqchip_in_use)) { + if (kvm_timer_should_notify_user(vcpu) || + kvm_pmu_should_notify_user(vcpu)) { + ret = -EINTR; + run->exit_reason = KVM_EXIT_INTR; + } + } + /* * Ensure we set mode to IN_GUEST_MODE after we disable * interrupts and before the final VCPU requests check. @@ -688,7 +711,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) kvm_request_pending(vcpu)) { vcpu->mode = OUTSIDE_GUEST_MODE; kvm_pmu_sync_hwstate(vcpu); - kvm_timer_sync_hwstate(vcpu); + if (static_branch_unlikely(&userspace_irqchip_in_use)) + kvm_timer_sync_hwstate(vcpu); kvm_vgic_sync_hwstate(vcpu); local_irq_enable(); preempt_enable(); @@ -732,7 +756,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) * we don't want vtimer interrupts to race with syncing the * timer virtual interrupt state. */ - kvm_timer_sync_hwstate(vcpu); + if (static_branch_unlikely(&userspace_irqchip_in_use)) + kvm_timer_sync_hwstate(vcpu); /* * We may have taken a host interrupt in HYP mode (ie
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. Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org> --- arch/arm/include/asm/kvm_host.h | 2 ++ arch/arm64/include/asm/kvm_host.h | 2 ++ virt/kvm/arm/arch_timer.c | 6 ++-- virt/kvm/arm/arm.c | 59 ++++++++++++++++++++++++++++----------- 4 files changed, 50 insertions(+), 19 deletions(-)