ioapic: allow buggy guests mishandling level-triggered interrupts to make progress
It was found that Hyper-V 2016 on KVM in some configurations (q35 machine + piix4-usb-uhci) hangs on boot. Root-cause was that one of Hyper-V level-triggered interrupt handler performs EOI before fixing the cause of the interrupt. This results in IOAPIC keep re-raising the level-triggered interrupt after EOI because irq-line remains asserted. Gory details: https://www.spinics.net/lists/kvm/msg184484.html (the whole thread). Turns out we were dealing with similar issues before; in-kernel IOAPIC implementation has commit 184564efae4d ("kvm: ioapic: conditionally delay irq delivery duringeoi broadcast") which describes a very similar issue. Steal the idea from the above mentioned commit for IOAPIC implementation in QEMU. SUCCESSIVE_IRQ_MAX_COUNT, delay and the comment are borrowed as well. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> Message-Id: <20190402080215.10747-1-vkuznets@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@ -139,6 +139,15 @@ static void ioapic_service(IOAPICCommonState *s)
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}
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}
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#define SUCCESSIVE_IRQ_MAX_COUNT 10000
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static void delayed_ioapic_service_cb(void *opaque)
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{
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IOAPICCommonState *s = opaque;
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ioapic_service(s);
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}
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static void ioapic_set_irq(void *opaque, int vector, int level)
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{
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IOAPICCommonState *s = opaque;
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@ -222,13 +231,39 @@ void ioapic_eoi_broadcast(int vector)
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}
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for (n = 0; n < IOAPIC_NUM_PINS; n++) {
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entry = s->ioredtbl[n];
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if ((entry & IOAPIC_LVT_REMOTE_IRR)
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&& (entry & IOAPIC_VECTOR_MASK) == vector) {
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if ((entry & IOAPIC_VECTOR_MASK) != vector ||
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((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1) != IOAPIC_TRIGGER_LEVEL) {
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continue;
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}
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if (!(entry & IOAPIC_LVT_REMOTE_IRR)) {
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continue;
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}
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trace_ioapic_clear_remote_irr(n, vector);
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s->ioredtbl[n] = entry & ~IOAPIC_LVT_REMOTE_IRR;
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if (!(entry & IOAPIC_LVT_MASKED) && (s->irr & (1 << n))) {
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++s->irq_eoi[vector];
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if (s->irq_eoi[vector] >= SUCCESSIVE_IRQ_MAX_COUNT) {
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/*
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* Real hardware does not deliver the interrupt immediately
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* during eoi broadcast, and this lets a buggy guest make
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* slow progress even if it does not correctly handle a
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* level-triggered interrupt. Emulate this behavior if we
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* detect an interrupt storm.
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*/
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s->irq_eoi[vector] = 0;
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timer_mod_anticipate(s->delayed_ioapic_service_timer,
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qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
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NANOSECONDS_PER_SECOND / 100);
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trace_ioapic_eoi_delayed_reassert(vector);
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} else {
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ioapic_service(s);
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}
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} else {
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s->irq_eoi[vector] = 0;
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}
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}
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}
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@ -401,6 +436,9 @@ static void ioapic_realize(DeviceState *dev, Error **errp)
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memory_region_init_io(&s->io_memory, OBJECT(s), &ioapic_io_ops, s,
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"ioapic", 0x1000);
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s->delayed_ioapic_service_timer =
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timer_new_ns(QEMU_CLOCK_VIRTUAL, delayed_ioapic_service_cb, s);
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qdev_init_gpio_in(dev, ioapic_set_irq, IOAPIC_NUM_PINS);
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ioapics[ioapic_no] = s;
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@ -408,6 +446,14 @@ static void ioapic_realize(DeviceState *dev, Error **errp)
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qemu_add_machine_init_done_notifier(&s->machine_done);
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}
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static void ioapic_unrealize(DeviceState *dev, Error **errp)
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{
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IOAPICCommonState *s = IOAPIC_COMMON(dev);
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timer_del(s->delayed_ioapic_service_timer);
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timer_free(s->delayed_ioapic_service_timer);
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}
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static Property ioapic_properties[] = {
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DEFINE_PROP_UINT8("version", IOAPICCommonState, version, IOAPIC_VER_DEF),
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DEFINE_PROP_END_OF_LIST(),
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@ -419,6 +465,7 @@ static void ioapic_class_init(ObjectClass *klass, void *data)
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DeviceClass *dc = DEVICE_CLASS(klass);
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k->realize = ioapic_realize;
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k->unrealize = ioapic_unrealize;
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/*
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* If APIC is in kernel, we need to update the kernel cache after
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* migration, otherwise first 24 gsi routes will be invalid.
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@ -25,6 +25,7 @@ apic_mem_writel(uint64_t addr, uint32_t val) "0x%"PRIx64" = 0x%08x"
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ioapic_set_remote_irr(int n) "set remote irr for pin %d"
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ioapic_clear_remote_irr(int n, int vector) "clear remote irr for pin %d vector %d"
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ioapic_eoi_broadcast(int vector) "EOI broadcast for vector %d"
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ioapic_eoi_delayed_reassert(int vector) "delayed reassert on EOI broadcast for vector %d"
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ioapic_mem_read(uint8_t addr, uint8_t regsel, uint8_t size, uint32_t val) "ioapic mem read addr 0x%"PRIx8" regsel: 0x%"PRIx8" size 0x%"PRIx8" retval 0x%"PRIx32
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ioapic_mem_write(uint8_t addr, uint8_t regsel, uint8_t size, uint32_t val) "ioapic mem write addr 0x%"PRIx8" regsel: 0x%"PRIx8" size 0x%"PRIx8" val 0x%"PRIx32
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ioapic_set_irq(int vector, int level) "vector: %d level: %d"
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@ -96,6 +96,7 @@ typedef struct IOAPICCommonClass {
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SysBusDeviceClass parent_class;
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DeviceRealize realize;
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DeviceUnrealize unrealize;
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void (*pre_save)(IOAPICCommonState *s);
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void (*post_load)(IOAPICCommonState *s);
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} IOAPICCommonClass;
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@ -111,6 +112,8 @@ struct IOAPICCommonState {
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uint8_t version;
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uint64_t irq_count[IOAPIC_NUM_PINS];
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int irq_level[IOAPIC_NUM_PINS];
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int irq_eoi[IOAPIC_NUM_PINS];
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QEMUTimer *delayed_ioapic_service_timer;
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};
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void ioapic_reset_common(DeviceState *dev);
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