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    Subject[PATCH 3.10 242/250] kvm: exclude ioeventfd from counting kvm_io_range limit
    Date
    From: Amos Kong <akong@redhat.com>

    commit 6ea34c9b78c10289846db0abeebd6b84d5aca084 upstream.

    We can easily reach the 1000 limit by start VM with a couple
    hundred I/O devices (multifunction=on). The hardcode limit
    already been adjusted 3 times (6 ~ 200 ~ 300 ~ 1000).

    In userspace, we already have maximum file descriptor to
    limit ioeventfd count. But kvm_io_bus devices also are used
    for pit, pic, ioapic, coalesced_mmio. They couldn't be limited
    by maximum file descriptor.

    Currently only ioeventfds take too much kvm_io_bus devices,
    so just exclude it from counting kvm_io_range limit.

    Also fixed one indent issue in kvm_host.h

    Signed-off-by: Amos Kong <akong@redhat.com>
    Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
    Signed-off-by: Gleb Natapov <gleb@redhat.com>
    [wt: next patch depends on this one]
    Signed-off-by: Willy Tarreau <w@1wt.eu>
    ---
    include/linux/kvm_host.h | 3 ++-
    virt/kvm/eventfd.c | 2 ++
    virt/kvm/kvm_main.c | 3 ++-
    3 files changed, 6 insertions(+), 2 deletions(-)

    diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    index 8db53cf..cbe9083 100644
    --- a/include/linux/kvm_host.h
    +++ b/include/linux/kvm_host.h
    @@ -145,7 +145,8 @@ struct kvm_io_range {
    #define NR_IOBUS_DEVS 1000

    struct kvm_io_bus {
    - int dev_count;
    + int dev_count;
    + int ioeventfd_count;
    struct kvm_io_range range[];
    };

    diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
    index 64ee720..1550637 100644
    --- a/virt/kvm/eventfd.c
    +++ b/virt/kvm/eventfd.c
    @@ -753,6 +753,7 @@ kvm_assign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
    if (ret < 0)
    goto unlock_fail;

    + kvm->buses[bus_idx]->ioeventfd_count++;
    list_add_tail(&p->list, &kvm->ioeventfds);

    mutex_unlock(&kvm->slots_lock);
    @@ -798,6 +799,7 @@ kvm_deassign_ioeventfd(struct kvm *kvm, struct kvm_ioeventfd *args)
    continue;

    kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev);
    + kvm->buses[bus_idx]->ioeventfd_count--;
    ioeventfd_release(p);
    ret = 0;
    break;
    diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
    index e9128725..36d14e5 100644
    --- a/virt/kvm/kvm_main.c
    +++ b/virt/kvm/kvm_main.c
    @@ -2936,7 +2936,8 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr,
    struct kvm_io_bus *new_bus, *bus;

    bus = kvm->buses[bus_idx];
    - if (bus->dev_count > NR_IOBUS_DEVS - 1)
    + /* exclude ioeventfd which is limited by maximum fd */
    + if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1)
    return -ENOSPC;

    new_bus = kzalloc(sizeof(*bus) + ((bus->dev_count + 1) *
    --
    2.8.0.rc2.1.gbe9624a
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