On 2012-03-13 13:00, Amos Kong wrote: > On 13/03/12 19:50, Jan Kiszka wrote: >> Please tag uq/master patches with "PATCH uq/master". >> >> On 2012-03-13 11:42, Amos Kong wrote: >>> Older kernels have a 6 device limit on the KVM io bus. >>> This patch makes kvm_has_many_ioeventfds() return available >>> ioeventfd count. ioeventfd will be disabled if there is >>> no 7 available ioeventfds. >>> >>> Signed-off-by: Amos Kong<akong@xxxxxxxxxx> >>> --- >>> hw/virtio-pci.c | 2 +- >>> kvm-all.c | 9 +++------ >>> 2 files changed, 4 insertions(+), 7 deletions(-) >>> >>> diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c >>> index a0fb7c1..d63f303 100644 >>> --- a/hw/virtio-pci.c >>> +++ b/hw/virtio-pci.c >>> @@ -678,7 +678,7 @@ void virtio_init_pci(VirtIOPCIProxy *proxy, VirtIODevice *vdev) >>> pci_register_bar(&proxy->pci_dev, 0, PCI_BASE_ADDRESS_SPACE_IO, >>> &proxy->bar); >>> >>> - if (!kvm_has_many_ioeventfds()) { >>> + if (kvm_has_many_ioeventfds() != 7) { >>> proxy->flags&= ~VIRTIO_PCI_FLAG_USE_IOEVENTFD; >>> } >>> >>> diff --git a/kvm-all.c b/kvm-all.c >>> index 3c6b4f0..d12694b 100644 >>> --- a/kvm-all.c >>> +++ b/kvm-all.c >>> @@ -78,7 +78,6 @@ struct KVMState >>> int pit_in_kernel; >>> int pit_state2; >>> int xsave, xcrs; >>> - int many_ioeventfds; >>> int irqchip_inject_ioctl; >>> #ifdef KVM_CAP_IRQ_ROUTING >>> struct kvm_irq_routing *irq_routes; >>> @@ -510,8 +509,8 @@ static int kvm_check_many_ioeventfds(void) >>> } >>> } >>> >>> - /* Decide whether many devices are supported or not */ >>> - ret = i == ARRAY_SIZE(ioeventfds); >>> + /* If i equals to 7, many devices are supported */ >>> + ret = i; >>> >>> while (i--> 0) { >>> kvm_set_ioeventfd_pio_word(ioeventfds[i], 0, i, false); >>> @@ -1078,8 +1077,6 @@ int kvm_init(void) >>> kvm_state = s; >>> memory_listener_register(&kvm_memory_listener, NULL); >>> >>> - s->many_ioeventfds = kvm_check_many_ioeventfds(); >>> - >>> cpu_interrupt_handler = kvm_handle_interrupt; >>> >>> return 0; >>> @@ -1407,7 +1404,7 @@ int kvm_has_many_ioeventfds(void) >>> if (!kvm_enabled()) { >>> return 0; >>> } >>> - return kvm_state->many_ioeventfds; >>> + return kvm_check_many_ioeventfds(); >> >> And why are you dropping the caching of the kvm_check_many_ioeventfds() >> return value? Is kvm_has_many_ioeventfds not used outside init scopes? > > Hi Jan, > > In the past, kvm_state->many_ioeventfds is only updated once at the > beginning, And the additional use case of patch 2 is not hot path either, right? > I want to use kvm_check_many_ioeventfds() to check if available > ioeventfd exists > before starting ioeventfd each time. OK, but than kvm_has_many_ioeventfds is not the right name for this function anymore. Call it "kvm_get_available_ioventfds" or so, but not in a away that implies a boolean return value. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- 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