On 03/09/15 18:23, Christoffer Dall wrote: > On Thu, Sep 03, 2015 at 06:06:39PM +0100, Marc Zyngier wrote: >> On 30/08/15 14:54, Christoffer Dall wrote: >>> The arch timer currently uses edge-triggered semantics in the sense that >>> the line is never sampled by the vgic and lowering the line from the >>> timer to the vgic doesn't have any affect on the pending state of >>> virtual interrupts in the vgic. This means that we do not support a >>> guest with the otherwise valid behavior of (1) disable interrupts (2) >>> enable the timer (3) disable the timer (4) enable interrupts. Such a >>> guest would validly not expect to see any interrupts on real hardware, >>> but will see interrupts on KVM. >>> >>> This patches fixes this shortcoming through the following series of >>> changes. >>> >>> First, we change the flow of the timer/vgic sync/flush operations. Now >>> the timer is always flushed/synced before the vgic, because the vgic >>> samples the state of the timer output. This has the implication that we >>> move the timer operations in to non-preempible sections, but that is >>> fine after the previous commit getting rid of hrtimer schedules on every >>> entry/exit. >>> >>> Second, we change the internal behavior of the timer, letting the timer >>> keep track of its previous output state, and only lower/raise the line >>> to the vgic when the state changes. Note that in theory this could have >>> been accomplished more simply by signalling the vgic every time the >>> state *potentially* changed, but we don't want to be hitting the vgic >>> more often than necessary. >>> >>> Third, we get rid of the use of the map->active field in the vgic and >>> instead simply set the interrupt as active on the physical distributor >>> whenever we signal a mapped interrupt to the guest, and we reset the >>> active state when we sync back the HW state from the vgic. >>> >>> Fourth, and finally, we now initialize the timer PPIs (and all the other >>> unused PPIs for now), to be level-triggered, and modify the sync code to >>> sample the line state on HW sync and re-inject a new interrupt if it is >>> still pending at that time. >>> >>> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> >>> --- >>> arch/arm/kvm/arm.c | 11 +++++-- >>> include/kvm/arm_arch_timer.h | 2 +- >>> include/kvm/arm_vgic.h | 3 -- >>> virt/kvm/arm/arch_timer.c | 68 +++++++++++++++++++++++++++++++------------- >>> virt/kvm/arm/vgic.c | 67 +++++++++++++++---------------------------- >>> 5 files changed, 81 insertions(+), 70 deletions(-) >>> >>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c >>> index bdf8871..102a4aa 100644 >>> --- a/arch/arm/kvm/arm.c >>> +++ b/arch/arm/kvm/arm.c >>> @@ -561,9 +561,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) >>> >>> if (ret <= 0 || need_new_vmid_gen(vcpu->kvm)) { >>> local_irq_enable(); >>> + kvm_timer_sync_hwstate(vcpu); >>> kvm_vgic_sync_hwstate(vcpu); >>> preempt_enable(); >>> - kvm_timer_sync_hwstate(vcpu); >>> continue; >>> } >>> >>> @@ -608,12 +608,17 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run) >>> kvm_guest_exit(); >>> trace_kvm_exit(kvm_vcpu_trap_get_class(vcpu), *vcpu_pc(vcpu)); >>> >>> + /* >>> + * We must sync the timer state before the vgic state so that >>> + * the vgic can properly sample the updated state of the >>> + * interrupt line. >>> + */ >>> + kvm_timer_sync_hwstate(vcpu); >>> + >>> kvm_vgic_sync_hwstate(vcpu); >>> >>> preempt_enable(); >>> >>> - kvm_timer_sync_hwstate(vcpu); >>> - >>> ret = handle_exit(vcpu, run, ret); >>> } >>> >>> diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h >>> index ef14cc1..1800227 100644 >>> --- a/include/kvm/arm_arch_timer.h >>> +++ b/include/kvm/arm_arch_timer.h >>> @@ -51,7 +51,7 @@ struct arch_timer_cpu { >>> bool armed; >>> >>> /* Timer IRQ */ >>> - const struct kvm_irq_level *irq; >>> + struct kvm_irq_level irq; >>> >>> /* VGIC mapping */ >>> struct irq_phys_map *map; >>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h >>> index d901f1a..99011a0 100644 >>> --- a/include/kvm/arm_vgic.h >>> +++ b/include/kvm/arm_vgic.h >>> @@ -163,7 +163,6 @@ struct irq_phys_map { >>> u32 virt_irq; >>> u32 phys_irq; >>> u32 irq; >>> - bool active; >>> }; >>> >>> struct irq_phys_map_entry { >>> @@ -358,8 +357,6 @@ int kvm_vgic_vcpu_active_irq(struct kvm_vcpu *vcpu); >>> struct irq_phys_map *kvm_vgic_map_phys_irq(struct kvm_vcpu *vcpu, >>> int virt_irq, int irq); >>> int kvm_vgic_unmap_phys_irq(struct kvm_vcpu *vcpu, struct irq_phys_map *map); >>> -bool kvm_vgic_get_phys_irq_active(struct irq_phys_map *map); >>> -void kvm_vgic_set_phys_irq_active(struct irq_phys_map *map, bool active); >>> >>> #define irqchip_in_kernel(k) (!!((k)->arch.vgic.in_kernel)) >>> #define vgic_initialized(k) (!!((k)->arch.vgic.nr_cpus)) >>> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c >>> index 018f3d6..747302f 100644 >>> --- a/virt/kvm/arm/arch_timer.c >>> +++ b/virt/kvm/arm/arch_timer.c >>> @@ -59,18 +59,6 @@ static void timer_disarm(struct arch_timer_cpu *timer) >>> } >>> } >>> >>> -static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu) >>> -{ >>> - int ret; >>> - struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >>> - >>> - kvm_vgic_set_phys_irq_active(timer->map, true); >>> - ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id, >>> - timer->map, >>> - timer->irq->level); >>> - WARN_ON(ret); >>> -} >>> - >>> static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id) >>> { >>> struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id; >>> @@ -116,8 +104,7 @@ static bool kvm_timer_irq_enabled(struct kvm_vcpu *vcpu) >>> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >>> >>> return !(timer->cntv_ctl & ARCH_TIMER_CTRL_IT_MASK) && >>> - (timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE) && >>> - !kvm_vgic_get_phys_irq_active(timer->map); >>> + (timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE); >>> } >>> >>> bool kvm_timer_should_fire(struct kvm_vcpu *vcpu) >>> @@ -134,6 +121,45 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu) >>> return cval <= now; >>> } >>> >>> +static void kvm_timer_update_irq(struct kvm_vcpu *vcpu) >>> +{ >>> + int ret; >>> + struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >>> + >>> + BUG_ON(!vgic_initialized(vcpu->kvm)); >>> + >>> + ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id, >>> + timer->map, >>> + timer->irq.level); >>> + WARN_ON(ret); >>> +} >>> + >>> +/* >>> + * Check if there was a change in the timer state (should we raise or lower >>> + * the line level to the GIC). >>> + */ >>> +static void kvm_timer_update_state(struct kvm_vcpu *vcpu) >>> +{ >>> + struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >>> + >>> + /* >>> + * If userspace modified the timer registers via SET_ONE_REG before >>> + * the vgic was initialized, we mustn't set the timer->irq.level value >>> + * because the guest would never see the interrupt. Instead wait >>> + * until we call this funciton from kvm_timer_flush_hwstate. >>> + */ >>> + if (!vgic_initialized(vcpu->kvm)) >>> + return; >>> + >>> + if (kvm_timer_should_fire(vcpu) && !timer->irq.level) { >>> + timer->irq.level = 1; >>> + kvm_timer_update_irq(vcpu); >>> + } else if (!kvm_timer_should_fire(vcpu) && timer->irq.level) { >>> + timer->irq.level = 0; >>> + kvm_timer_update_irq(vcpu); >>> + } >>> +} >>> + >> >> It took me ages to parse this, so I rewrote it to match my understanding: >> >> diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c >> index 8a0fdfc..a722f0f 100644 >> --- a/virt/kvm/arm/arch_timer.c >> +++ b/virt/kvm/arm/arch_timer.c >> @@ -121,13 +121,14 @@ bool kvm_timer_should_fire(struct kvm_vcpu *vcpu) >> return cval <= now; >> } >> >> -static void kvm_timer_update_irq(struct kvm_vcpu *vcpu) >> +static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_state) >> { >> int ret; >> struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; >> >> BUG_ON(!vgic_initialized(vcpu->kvm)); >> >> + timer->irq.level = new_state; >> ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id, >> timer->map, >> timer->irq.level); >> @@ -151,13 +152,8 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu) >> if (!vgic_initialized(vcpu->kvm)) >> return; >> >> - if (kvm_timer_should_fire(vcpu) && !timer->irq.level) { >> - timer->irq.level = 1; >> - kvm_timer_update_irq(vcpu); >> - } else if (!kvm_timer_should_fire(vcpu) && timer->irq.level) { >> - timer->irq.level = 0; >> - kvm_timer_update_irq(vcpu); >> - } >> + if (kvm_timer_should_fire(vcpu) != timer->irq.level) >> + kvm_timer_update_irq(vcpu, !timer->irq.level); >> } >> >> /* >> >> Did I get it right? > > almost, you'd have to assign timer->irq.level after you check for it > though, right? That's why I've added this line in kvm_timer_update_irq()! :-) >> >>> /* >>> * Schedule the background timer before calling kvm_vcpu_block, so that this >>> * thread is removed from its waitqueue and made runnable when there's a timer >>> @@ -191,8 +217,7 @@ void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu) >>> * If the timer expired while we were not scheduled, now is the time >>> * to inject it. >>> */ >>> - if (kvm_timer_should_fire(vcpu)) >>> - kvm_timer_inject_irq(vcpu); >>> + kvm_timer_update_state(vcpu); >>> } >>> >>> /** >>> @@ -208,8 +233,11 @@ void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu) >>> >>> BUG_ON(timer_is_armed(timer)); >>> >>> - if (kvm_timer_should_fire(vcpu)) >>> - kvm_timer_inject_irq(vcpu); >>> + /* >>> + * The guest could have modified the timer registers or the timer >>> + * could have expired, update the timer state. >>> + */ >>> + kvm_timer_update_state(vcpu); >>> } >>> >>> int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu, >>> @@ -224,7 +252,7 @@ int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu, >>> * kvm_vcpu_set_target(). To handle this, we determine >>> * vcpu timer irq number when the vcpu is reset. >>> */ >>> - timer->irq = irq; >>> + timer->irq.irq = irq->irq; >>> >>> /* >>> * Tell the VGIC that the virtual interrupt is tied to a >>> @@ -269,6 +297,8 @@ int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value) >>> default: >>> return -1; >>> } >>> + >>> + kvm_timer_update_state(vcpu); >>> return 0; >>> } >>> >>> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c >>> index 9ed8d53..f4ea950 100644 >>> --- a/virt/kvm/arm/vgic.c >>> +++ b/virt/kvm/arm/vgic.c >>> @@ -1422,34 +1422,43 @@ static bool vgic_process_maintenance(struct kvm_vcpu *vcpu) >>> /* >>> * Save the physical active state, and reset it to inactive. >>> * >>> - * Return 1 if HW interrupt went from active to inactive, and 0 otherwise. >>> + * Return true if there's a pending level triggered interrupt line to queue. >>> */ >>> -static int vgic_sync_hwirq(struct kvm_vcpu *vcpu, struct vgic_lr vlr) >>> +static bool vgic_sync_hwirq(struct kvm_vcpu *vcpu, int lr, struct vgic_lr vlr) >>> { >>> struct irq_phys_map *map; >>> + bool phys_active; >>> int ret; >>> >>> if (!(vlr.state & LR_HW)) >>> return 0; >>> >>> map = vgic_irq_map_search(vcpu, vlr.irq); >>> - BUG_ON(!map || !map->active); >>> + BUG_ON(!map); >>> >>> ret = irq_get_irqchip_state(map->irq, >>> IRQCHIP_STATE_ACTIVE, >>> - &map->active); >>> + &phys_active); >>> >>> WARN_ON(ret); >>> >>> - if (map->active) { >>> + if (phys_active) { >>> + /* >>> + * Interrupt still marked as active on the physical >>> + * distributor, so guest did not EOI it yet. Reset to >>> + * non-active so that other VMs can see interrupts from this >>> + * device. >>> + */ >>> ret = irq_set_irqchip_state(map->irq, >>> IRQCHIP_STATE_ACTIVE, >>> false); >>> WARN_ON(ret); >>> - return 0; >>> + return false; >>> } >>> >>> - return 1; >>> + /* Mapped edge-triggered interrupts not yet supported. */ >>> + WARN_ON(vgic_irq_is_edge(vcpu, vlr.irq)); >> >> Hmmm. What are we missing? >> > > I don't know really, my brain ran out of memory, but it's not like we > claimed to support this earlier and clearly we didn't work this well > enough through. We can definitely revisit this later, but I have the feeling that the flow is quite similar... > >>> + return process_level_irq(vcpu, lr, vlr); >>> } >>> >>> /* Sync back the VGIC state after a guest run */ >>> @@ -1474,18 +1483,8 @@ static void __kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu) >>> continue; >>> >>> vlr = vgic_get_lr(vcpu, lr); >>> - if (vgic_sync_hwirq(vcpu, vlr)) { >>> - /* >>> - * So this is a HW interrupt that the guest >>> - * EOI-ed. Clean the LR state and allow the >>> - * interrupt to be sampled again. >>> - */ >>> - vlr.state = 0; >>> - vlr.hwirq = 0; >>> - vgic_set_lr(vcpu, lr, vlr); >>> - vgic_irq_clear_queued(vcpu, vlr.irq); >>> - set_bit(lr, elrsr_ptr); >>> - } >>> + if (vgic_sync_hwirq(vcpu, lr, vlr)) >>> + level_pending = true; >>> >>> if (!test_bit(lr, elrsr_ptr)) >>> continue; >>> @@ -1861,30 +1860,6 @@ static void vgic_free_phys_irq_map_rcu(struct rcu_head *rcu) >>> } >>> >>> /** >>> - * kvm_vgic_get_phys_irq_active - Return the active state of a mapped IRQ >>> - * >>> - * Return the logical active state of a mapped interrupt. This doesn't >>> - * necessarily reflects the current HW state. >>> - */ >>> -bool kvm_vgic_get_phys_irq_active(struct irq_phys_map *map) >>> -{ >>> - BUG_ON(!map); >>> - return map->active; >>> -} >>> - >>> -/** >>> - * kvm_vgic_set_phys_irq_active - Set the active state of a mapped IRQ >>> - * >>> - * Set the logical active state of a mapped interrupt. This doesn't >>> - * immediately affects the HW state. >>> - */ >>> -void kvm_vgic_set_phys_irq_active(struct irq_phys_map *map, bool active) >>> -{ >>> - BUG_ON(!map); >>> - map->active = active; >>> -} >>> - >>> -/** >>> * kvm_vgic_unmap_phys_irq - Remove a virtual to physical IRQ mapping >>> * @vcpu: The VCPU pointer >>> * @map: The pointer to a mapping obtained through kvm_vgic_map_phys_irq >>> @@ -2112,10 +2087,14 @@ int vgic_init(struct kvm *kvm) >>> if (i < VGIC_NR_SGIS) >>> vgic_bitmap_set_irq_val(&dist->irq_enabled, >>> vcpu->vcpu_id, i, 1); >>> - if (i < VGIC_NR_PRIVATE_IRQS) >>> + if (i < VGIC_NR_SGIS) >>> vgic_bitmap_set_irq_val(&dist->irq_cfg, >>> vcpu->vcpu_id, i, >>> VGIC_CFG_EDGE); >>> + else if (i < VGIC_NR_PRIVATE_IRQS) /* PPIs */ >>> + vgic_bitmap_set_irq_val(&dist->irq_cfg, >>> + vcpu->vcpu_id, i, >>> + VGIC_CFG_LEVEL); >>> } >>> >>> vgic_enable(vcpu); >>> >> >> My only real objection to this patch is that it puts my brain upside down. >> Hopefully that won't last. >> > Yeah, I tried helping in the commit message, but I couldn't do much > beyond that. Splitting up the patch further didn't really work out for > me. It is indeed quite intricated, and hard to really take apart. Guess we'll have to live with it. Thanks, M. -- Jazz is not dead. It just smells funny... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html