On Thu, Sep 03, 2015 at 06:29:14PM +0100, Marc Zyngier wrote: > 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()! :-) > duh, /me learns to read diffs all over again. Yeah, your version is probably easier to read. thanks. > >> > >>> /* > >>> * 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