[Qemu-devel] [Bug 1465935] Re: kvm_irqchip_commit_routes: Assertion `ret == 0' failed

[Li Chengyuan]

>From kvm_pc_setup_irq_routing() function, we can see that 15 routes from
PIC and 23 routes from IOAPIC are added into irq route table, but only
23 irq(gsi) are reserved. This leads to irq route table has been full
but there are still tens of free gsi. So the "retry" part of
kvm_irqchip_get_virq() shall never have chance to be executed.


void kvm_pc_setup_irq_routing(bool pci_enabled)
{
    KVMState *s = kvm_state;
    int i;

    if (kvm_check_extension(s, KVM_CAP_IRQ_ROUTING)) {
        for (i = 0; i < 8; ++i) {
            if (i == 2) {
                continue;
            }
            kvm_irqchip_add_irq_route(s, i, KVM_IRQCHIP_PIC_MASTER, i);
        }
        for (i = 8; i < 16; ++i) {
            kvm_irqchip_add_irq_route(s, i, KVM_IRQCHIP_PIC_SLAVE, i - 8);
        }
        if (pci_enabled) {
            for (i = 0; i < 24; ++i) {
                if (i == 0) {
                    kvm_irqchip_add_irq_route(s, i, KVM_IRQCHIP_IOAPIC, 2);
                } else if (i != 2) {
                    kvm_irqchip_add_irq_route(s, i, KVM_IRQCHIP_IOAPIC, i);
                }
            }
        }
        kvm_irqchip_commit_routes(s);
    }
}

static int kvm_irqchip_get_virq(KVMState *s)
{
    uint32_t *word = s->used_gsi_bitmap;
    int max_words = ALIGN(s->gsi_count, 32) / 32;
    int i, bit;
    bool retry = true;

again:
    /* Return the lowest unused GSI in the bitmap */
    for (i = 0; i < max_words; i++) {
        bit = ffs(~word[i]);
        if (!bit) {
            continue;
        }

        return bit - 1 + i * 32;
    }
    if (!s->direct_msi && retry) {
        retry = false;
        kvm_flush_dynamic_msi_routes(s);
        goto again;
    }
    return -ENOSPC;

}

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https://bugs.launchpad.net/bugs/1465935

Title:
  kvm_irqchip_commit_routes: Assertion `ret == 0' failed

Status in QEMU:
  New
Status in qemu package in Ubuntu:
  New

Bug description:
  Several my QEMU instances crashed, and in the  qemu log, I can see
  this assertion failure,

     qemu-system-x86_64: /build/buildd/qemu-2.0.0+dfsg/kvm-all.c:984:
  kvm_irqchip_commit_routes: Assertion `ret == 0' failed.

  The QEMU version is 2.0.0, HV OS is ubuntu 12.04, kernel 3.2.0-38.
  Guest OS is RHEL 6.3.

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