From: Christoffer Dall <christoffer.dall@linaro.org> To: kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Cc: Marc Zyngier <marc.zyngier@arm.com>, Christoffer Dall <cdall@linaro.org>, Shih-Wei Li <shihwei@cs.columbia.edu>, kvm@vger.kernel.org Subject: [PATCH v4 18/20] KVM: arm/arm64: Avoid phys timer emulation in vcpu entry/exit Date: Fri, 20 Oct 2017 13:49:37 +0200 [thread overview] Message-ID: <20171020114939.12554-19-christoffer.dall@linaro.org> (raw) In-Reply-To: <20171020114939.12554-1-christoffer.dall@linaro.org> From: Christoffer Dall <cdall@linaro.org> There is no need to schedule and cancel a hrtimer when entering and exiting the guest, because we know when the physical timer is going to fire when the guest programs it, and we can simply program the hrtimer at that point. Now when the register modifications from the guest go through the kvm_arm_timer_set/get_reg functions, which always call kvm_timer_update_state(), we can simply consider the timer state in this function and schedule and cancel the timers as needed. This avoids looking at the physical timer emulation state when entering and exiting the VCPU, allowing for faster servicing of the VM when needed. Signed-off-by: Christoffer Dall <cdall@linaro.org> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> --- virt/kvm/arm/arch_timer.c | 76 +++++++++++++++++++++++++++++++---------------- 1 file changed, 51 insertions(+), 25 deletions(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 7f4f12d48a1a..c7499364f2ed 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -202,7 +202,27 @@ static enum hrtimer_restart kvm_bg_timer_expire(struct hrtimer *hrt) static enum hrtimer_restart kvm_phys_timer_expire(struct hrtimer *hrt) { - WARN(1, "Timer only used to ensure guest exit - unexpected event."); + struct arch_timer_context *ptimer; + struct arch_timer_cpu *timer; + struct kvm_vcpu *vcpu; + u64 ns; + + timer = container_of(hrt, struct arch_timer_cpu, phys_timer); + vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu); + ptimer = vcpu_ptimer(vcpu); + + /* + * Check that the timer has really expired from the guest's + * PoV (NTP on the host may have forced it to expire + * early). If not ready, schedule for a later time. + */ + ns = kvm_timer_compute_delta(ptimer); + if (unlikely(ns)) { + hrtimer_forward_now(hrt, ns_to_ktime(ns)); + return HRTIMER_RESTART; + } + + kvm_timer_update_irq(vcpu, true, ptimer); return HRTIMER_NORESTART; } @@ -256,24 +276,28 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, } /* Schedule the background timer for the emulated timer. */ -static void phys_timer_emulate(struct kvm_vcpu *vcpu, - struct arch_timer_context *timer_ctx) +static void phys_timer_emulate(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; + struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); - if (kvm_timer_should_fire(timer_ctx)) - return; - - if (!kvm_timer_irq_can_fire(timer_ctx)) + /* + * If the timer can fire now we have just raised the IRQ line and we + * don't need to have a soft timer scheduled for the future. If the + * timer cannot fire at all, then we also don't need a soft timer. + */ + if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer)) { + soft_timer_cancel(&timer->phys_timer, NULL); return; + } - /* The timer has not yet expired, schedule a background timer */ - soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(timer_ctx)); + soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(ptimer)); } /* - * Check if there was a change in the timer state (should we raise or lower - * the line level to the GIC). + * Check if there was a change in the timer state, so that we should either + * raise or lower the line level to the GIC or schedule a background timer to + * emulate the physical timer. */ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) { @@ -295,6 +319,8 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) if (kvm_timer_should_fire(ptimer) != ptimer->irq.level) kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer); + + phys_timer_emulate(vcpu); } static void vtimer_save_state(struct kvm_vcpu *vcpu) @@ -441,6 +467,9 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu) if (has_vhe()) disable_el1_phys_timer_access(); + + /* Set the background timer for the physical timer emulation. */ + phys_timer_emulate(vcpu); } bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu) @@ -472,16 +501,9 @@ bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu) void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; - struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); if (unlikely(!timer->enabled)) return; - - if (kvm_timer_should_fire(ptimer) != ptimer->irq.level) - kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer); - - /* Set the background timer for the physical timer emulation. */ - phys_timer_emulate(vcpu, vcpu_ptimer(vcpu)); } void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) @@ -496,6 +518,17 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) vtimer_save_state(vcpu); + /* + * Cancel the physical timer emulation, because the only case where we + * need it after a vcpu_put is in the context of a sleeping VCPU, and + * in that case we already factor in the deadline for the physical + * timer when scheduling the bg_timer. + * + * In any case, we re-schedule the hrtimer for the physical timer when + * coming back to the VCPU thread in kvm_timer_vcpu_load(). + */ + soft_timer_cancel(&timer->phys_timer, NULL); + /* * The kernel may decide to run userspace after calling vcpu_put, so * we reset cntvoff to 0 to ensure a consistent read between user @@ -538,15 +571,8 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu) */ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu) { - struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); - /* - * This is to cancel the background timer for the physical timer - * emulation if it is set. - */ - soft_timer_cancel(&timer->phys_timer, NULL); - /* * If we entered the guest with the vtimer output asserted we have to * check if the guest has modified the timer so that we should lower -- 2.14.2
WARNING: multiple messages have this Message-ID (diff)
From: christoffer.dall@linaro.org (Christoffer Dall) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v4 18/20] KVM: arm/arm64: Avoid phys timer emulation in vcpu entry/exit Date: Fri, 20 Oct 2017 13:49:37 +0200 [thread overview] Message-ID: <20171020114939.12554-19-christoffer.dall@linaro.org> (raw) In-Reply-To: <20171020114939.12554-1-christoffer.dall@linaro.org> From: Christoffer Dall <cdall@linaro.org> There is no need to schedule and cancel a hrtimer when entering and exiting the guest, because we know when the physical timer is going to fire when the guest programs it, and we can simply program the hrtimer at that point. Now when the register modifications from the guest go through the kvm_arm_timer_set/get_reg functions, which always call kvm_timer_update_state(), we can simply consider the timer state in this function and schedule and cancel the timers as needed. This avoids looking at the physical timer emulation state when entering and exiting the VCPU, allowing for faster servicing of the VM when needed. Signed-off-by: Christoffer Dall <cdall@linaro.org> Reviewed-by: Marc Zyngier <marc.zyngier@arm.com> --- virt/kvm/arm/arch_timer.c | 76 +++++++++++++++++++++++++++++++---------------- 1 file changed, 51 insertions(+), 25 deletions(-) diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c index 7f4f12d48a1a..c7499364f2ed 100644 --- a/virt/kvm/arm/arch_timer.c +++ b/virt/kvm/arm/arch_timer.c @@ -202,7 +202,27 @@ static enum hrtimer_restart kvm_bg_timer_expire(struct hrtimer *hrt) static enum hrtimer_restart kvm_phys_timer_expire(struct hrtimer *hrt) { - WARN(1, "Timer only used to ensure guest exit - unexpected event."); + struct arch_timer_context *ptimer; + struct arch_timer_cpu *timer; + struct kvm_vcpu *vcpu; + u64 ns; + + timer = container_of(hrt, struct arch_timer_cpu, phys_timer); + vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu); + ptimer = vcpu_ptimer(vcpu); + + /* + * Check that the timer has really expired from the guest's + * PoV (NTP on the host may have forced it to expire + * early). If not ready, schedule for a later time. + */ + ns = kvm_timer_compute_delta(ptimer); + if (unlikely(ns)) { + hrtimer_forward_now(hrt, ns_to_ktime(ns)); + return HRTIMER_RESTART; + } + + kvm_timer_update_irq(vcpu, true, ptimer); return HRTIMER_NORESTART; } @@ -256,24 +276,28 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level, } /* Schedule the background timer for the emulated timer. */ -static void phys_timer_emulate(struct kvm_vcpu *vcpu, - struct arch_timer_context *timer_ctx) +static void phys_timer_emulate(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; + struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); - if (kvm_timer_should_fire(timer_ctx)) - return; - - if (!kvm_timer_irq_can_fire(timer_ctx)) + /* + * If the timer can fire now we have just raised the IRQ line and we + * don't need to have a soft timer scheduled for the future. If the + * timer cannot fire at all, then we also don't need a soft timer. + */ + if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer)) { + soft_timer_cancel(&timer->phys_timer, NULL); return; + } - /* The timer has not yet expired, schedule a background timer */ - soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(timer_ctx)); + soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(ptimer)); } /* - * Check if there was a change in the timer state (should we raise or lower - * the line level to the GIC). + * Check if there was a change in the timer state, so that we should either + * raise or lower the line level to the GIC or schedule a background timer to + * emulate the physical timer. */ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) { @@ -295,6 +319,8 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) if (kvm_timer_should_fire(ptimer) != ptimer->irq.level) kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer); + + phys_timer_emulate(vcpu); } static void vtimer_save_state(struct kvm_vcpu *vcpu) @@ -441,6 +467,9 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu) if (has_vhe()) disable_el1_phys_timer_access(); + + /* Set the background timer for the physical timer emulation. */ + phys_timer_emulate(vcpu); } bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu) @@ -472,16 +501,9 @@ bool kvm_timer_should_notify_user(struct kvm_vcpu *vcpu) void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu) { struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; - struct arch_timer_context *ptimer = vcpu_ptimer(vcpu); if (unlikely(!timer->enabled)) return; - - if (kvm_timer_should_fire(ptimer) != ptimer->irq.level) - kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer); - - /* Set the background timer for the physical timer emulation. */ - phys_timer_emulate(vcpu, vcpu_ptimer(vcpu)); } void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) @@ -496,6 +518,17 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu) vtimer_save_state(vcpu); + /* + * Cancel the physical timer emulation, because the only case where we + * need it after a vcpu_put is in the context of a sleeping VCPU, and + * in that case we already factor in the deadline for the physical + * timer when scheduling the bg_timer. + * + * In any case, we re-schedule the hrtimer for the physical timer when + * coming back to the VCPU thread in kvm_timer_vcpu_load(). + */ + soft_timer_cancel(&timer->phys_timer, NULL); + /* * The kernel may decide to run userspace after calling vcpu_put, so * we reset cntvoff to 0 to ensure a consistent read between user @@ -538,15 +571,8 @@ static void unmask_vtimer_irq(struct kvm_vcpu *vcpu) */ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu) { - struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; struct arch_timer_context *vtimer = vcpu_vtimer(vcpu); - /* - * This is to cancel the background timer for the physical timer - * emulation if it is set. - */ - soft_timer_cancel(&timer->phys_timer, NULL); - /* * If we entered the guest with the vtimer output asserted we have to * check if the guest has modified the timer so that we should lower -- 2.14.2
next prev parent reply other threads:[~2017-10-20 11:49 UTC|newest] Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-10-20 11:49 [PATCH v4 00/20] KVM: arm/arm64: Optimize arch timer register handling Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 01/20] irqchip/gic: Deal with broken firmware exposing only 4kB of GICv2 CPU interface Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 02/20] arm64: Implement arch_counter_get_cntpct to read the physical counter Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:41 ` Marc Zyngier 2017-10-25 13:41 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 03/20] arm64: Use physical counter for in-kernel reads when booted in EL2 Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:43 ` Marc Zyngier 2017-10-25 13:43 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 04/20] KVM: arm/arm64: Guard kvm_vgic_map_is_active against !vgic_initialized Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 05/20] KVM: arm/arm64: Support calling vgic_update_irq_pending from irq context Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:45 ` Marc Zyngier 2017-10-25 13:45 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 06/20] KVM: arm/arm64: Check that system supports split eoi/deactivate Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:47 ` Marc Zyngier 2017-10-25 13:47 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 07/20] KVM: arm/arm64: Make timer_arm and timer_disarm helpers more generic Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:49 ` Marc Zyngier 2017-10-25 13:49 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 08/20] KVM: arm/arm64: Rename soft timer to bg_timer Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 09/20] KVM: arm/arm64: Move timer/vgic flush/sync under disabled irq Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 10/20] KVM: arm/arm64: Use separate timer for phys timer emulation Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 13:59 ` Marc Zyngier 2017-10-25 13:59 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 11/20] KVM: arm/arm64: Move timer save/restore out of the hyp code Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 12/20] genirq: Document vcpu_info usage for percpu_devid interrupts Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:56 ` Thomas Gleixner 2017-10-20 11:56 ` Thomas Gleixner 2017-10-21 14:29 ` Christoffer Dall 2017-10-21 14:29 ` Christoffer Dall 2017-10-21 14:55 ` Thomas Gleixner 2017-10-21 14:55 ` Thomas Gleixner 2017-10-21 15:30 ` Christoffer Dall 2017-10-21 15:30 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 13/20] KVM: arm/arm64: Set VCPU affinity for virt timer irq Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 14/20] KVM: arm/arm64: Avoid timer save/restore in vcpu entry/exit Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 14:36 ` Marc Zyngier 2017-10-25 14:36 ` Marc Zyngier 2017-11-16 20:30 ` Jintack Lim 2017-11-16 20:30 ` Jintack Lim 2017-11-16 20:32 ` Jintack Lim 2017-11-16 20:32 ` Jintack Lim 2017-11-20 11:15 ` Christoffer Dall 2017-11-20 11:15 ` Christoffer Dall 2017-11-20 16:32 ` Jintack Lim 2017-11-20 16:32 ` Jintack Lim 2017-10-20 11:49 ` [PATCH v4 15/20] KVM: arm/arm64: Support EL1 phys timer register access in set/get reg Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-25 14:38 ` Marc Zyngier 2017-10-25 14:38 ` Marc Zyngier 2017-10-20 11:49 ` [PATCH v4 16/20] KVM: arm/arm64: Use kvm_arm_timer_set/get_reg for guest register traps Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 17/20] KVM: arm/arm64: Move phys_timer_emulate function Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall [this message] 2017-10-20 11:49 ` [PATCH v4 18/20] KVM: arm/arm64: Avoid phys timer emulation in vcpu entry/exit Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 19/20] KVM: arm/arm64: Get rid of kvm_timer_flush_hwstate Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall 2017-10-20 11:49 ` [PATCH v4 20/20] KVM: arm/arm64: Rework kvm_timer_should_fire Christoffer Dall 2017-10-20 11:49 ` Christoffer Dall
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