Re: [PATCH 1/2] return available ioeventfds count in kvm_has_many_ioeventfds()

[Jan Kiszka <jan.kiszka@siemens.com>]

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@redhat.com>
> ---
>  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?

Jan

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