Last month, we experienced several guests crash(6cores-8cores),qemu logs display the following messages:
qemu-system-x86_64: /build/qemu-2.1.2/kvm-all.c:976: kvm_irqchip_commit_routes: Assertion `ret == 0' failed. After analysis and verification, we can confirm it's irq-balance daemon(in guest) leads to the assertion failure.So start a 8 core guest with two disks, execute the following scripts will reproduce the BUG quickly: vda_irq_num=25 vdb_irq_num=27 while [ 1 ] do for irq in {1,2,4,8,10,20,40,80} do echo $irq > /proc/irq/$vda_irq_num/smp_affinity echo $irq > /proc/irq/$vdb_irq_num/smp_affinity dd if=/dev/vda of=/dev/zero bs=4K count=100 iflag=direct dd if=/dev/vdb of=/dev/zero bs=4K count=100 iflag=direct done done QEMU setup static irq route entries in kvm_pc_setup_irq_routing(),PIC and IOAPIC share the first 15 GSI numbers,take up 23 GSI numbers,but take up 38 irq route entries.When change irq smp_affinity in guest,a dynamic route entry may be setup,the current logic is:if allocate GSI number succeeds, a new route entry can be added.The available dynamic GSI numbers is 1021(KVM_MAX_IRQ_ROUTES-23),but available irq route entries is only 986(KVM_MAX_IRQ_ROUTES-38),GSI numbers greater than route entries. irq-balance's behavior will eventually leads to total irq route entries exceed KVM_MAX_IRQ_ROUTES,ioctl(KVM_SET_GSI_ROUTING) fail and kvm_irqchip_commit_routes() trigger assertion failure. This patch fix the BUG. Signed-off-by: Wenshuang Ma <kevin...@tencent.com> --- kvm-all.c | 11 +++++++++++ 1 files changed, 11 insertions(+), 0 deletions(-) diff --git a/kvm-all.c b/kvm-all.c index 18cc6b4..f47e1b1 100644 --- a/kvm-all.c +++ b/kvm-all.c @@ -1123,6 +1123,17 @@ static int kvm_irqchip_get_virq(KVMState *s) int i, bit; bool retry = true; + /* + * PIC and IOAPIC share the first 15 GSI numbers,available GSI + * numbers greater than IRQ route entries. If allocate GSI number + * succeeds, a new route entry can be added, so total IRQ route + * enties can exceed gsi_count, flush dynamic MSI entries when + * IRQ route entries arrive gsi_count. + */ + if (!s->direct_msi && s->irq_routes->nr == s->gsi_count) { + kvm_flush_dynamic_msi_routes(s); + } + again: /* Return the lowest unused GSI in the bitmap */ for (i = 0; i < max_words; i++) { -- 1.7.1