From 5a24575032971c5a9a4580417a791c427ebdb8e5 Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Fri, 8 Sep 2017 07:07:13 -0700 Subject: KVM: arm/arm64: Remove redundant preemptible checks The __this_cpu_read() and __this_cpu_write() functions already implement checks for the required preemption levels when using CONFIG_DEBUG_PREEMPT which gives you nice error messages and such. Therefore there is no need to explicitly check this using a BUG_ON() in the code (which we don't do for other uses of per cpu variables either). Acked-by: Marc Zyngier Reviewed-by: Andre Przywara Signed-off-by: Christoffer Dall --- virt/kvm/arm/arm.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'virt/kvm/arm/arm.c') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 6b60c98a6e22..3610e132df8b 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -71,7 +71,6 @@ static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled); static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu) { - BUG_ON(preemptible()); __this_cpu_write(kvm_arm_running_vcpu, vcpu); } @@ -81,7 +80,6 @@ static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu) */ struct kvm_vcpu *kvm_arm_get_running_vcpu(void) { - BUG_ON(preemptible()); return __this_cpu_read(kvm_arm_running_vcpu); } -- cgit v1.2.3 From 61bbe38027334780964e4b2658f722ed0b3cb2f9 Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Fri, 27 Oct 2017 19:57:51 +0200 Subject: 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 Signed-off-by: Christoffer Dall --- 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(-) (limited to 'virt/kvm/arm/arm.c') 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..59d8e04c19fa 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 signal 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 -- cgit v1.2.3 From 58d6b15e9da5042a99c9c30ad725792e4569150e Mon Sep 17 00:00:00 2001 From: James Morse Date: Mon, 22 Jan 2018 18:19:06 +0000 Subject: KVM: arm/arm64: Handle CPU_PM_ENTER_FAILED cpu_pm_enter() calls the pm notifier chain with CPU_PM_ENTER, then if there is a failure: CPU_PM_ENTER_FAILED. When KVM receives CPU_PM_ENTER it calls cpu_hyp_reset() which will return us to the hyp-stub. If we subsequently get a CPU_PM_ENTER_FAILED, KVM does nothing, leaving the CPU running with the hyp-stub, at odds with kvm_arm_hardware_enabled. Add CPU_PM_ENTER_FAILED as a fallthrough for CPU_PM_EXIT, this reloads KVM based on kvm_arm_hardware_enabled. This is safe even if CPU_PM_ENTER never gets as far as KVM, as cpu_hyp_reinit() calls cpu_hyp_reset() to make sure the hyp-stub is loaded before reloading KVM. Fixes: 67f691976662 ("arm64: kvm: allows kvm cpu hotplug") Cc: # v4.7+ CC: Lorenzo Pieralisi Reviewed-by: Christoffer Dall Signed-off-by: James Morse Signed-off-by: Christoffer Dall --- virt/kvm/arm/arm.c | 1 + 1 file changed, 1 insertion(+) (limited to 'virt/kvm/arm/arm.c') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 59d8e04c19fa..639dca0c0560 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -1262,6 +1262,7 @@ static int hyp_init_cpu_pm_notifier(struct notifier_block *self, cpu_hyp_reset(); return NOTIFY_OK; + case CPU_PM_ENTER_FAILED: case CPU_PM_EXIT: if (__this_cpu_read(kvm_arm_hardware_enabled)) /* The hardware was enabled before suspend. */ -- cgit v1.2.3 From f1d7231cede93a42d75b6d3c5ca599e94a273e89 Mon Sep 17 00:00:00 2001 From: Christoffer Dall Date: Thu, 25 Jan 2018 18:32:29 +0100 Subject: KVM: arm/arm64: Fix userspace_irqchip_in_use counting We were not decrementing the static key count in the right location. kvm_arch_vcpu_destroy() is only called to clean up after a failed VCPU create attempt, whereas kvm_arch_vcpu_free() is called on teardown of the VM as well. Move the static key decrement call to kvm_arch_vcpu_free(). Acked-by: Marc Zyngier Signed-off-by: Christoffer Dall --- virt/kvm/arm/arm.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'virt/kvm/arm/arm.c') diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c index 639dca0c0560..04ee7a327870 100644 --- a/virt/kvm/arm/arm.c +++ b/virt/kvm/arm/arm.c @@ -295,6 +295,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu) void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu) { + if (vcpu->arch.has_run_once && unlikely(!irqchip_in_kernel(vcpu->kvm))) + static_branch_dec(&userspace_irqchip_in_use); + kvm_mmu_free_memory_caches(vcpu); kvm_timer_vcpu_terminate(vcpu); kvm_pmu_vcpu_destroy(vcpu); @@ -304,8 +307,6 @@ 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); } -- cgit v1.2.3