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Date: Tue, 12 Jan 2010 16:35:17 -0600
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: [Qemu-devel] Re: [PATCH-RFC 02/13] kvm: add API to set ioeventfd
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

On 01/11/2010 11:17 AM, Michael S. Tsirkin wrote:
> Signed-off-by: Michael S. Tsirkin<mst@redhat.com>
> ---
>   kvm-all.c |   24 ++++++++++++++++++++++++
>   kvm.h     |    3 +++
>   2 files changed, 27 insertions(+), 0 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index a312654..aa00119 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -1113,3 +1113,27 @@ void kvm_remove_all_breakpoints(CPUState *current_env)
>   {
>   }
>   #endif /* !KVM_CAP_SET_GUEST_DEBUG */
> +
> +#ifdef KVM_IOEVENTFD
> +int kvm_set_ioeventfd(uint16_t addr, uint16_t data, int fd, bool assigned)
> +{
> +    struct kvm_ioeventfd kick = {
> +        .datamatch = data,
> +        .addr = addr,
> +        .len = 2,
> +        .flags = KVM_IOEVENTFD_FLAG_DATAMATCH | KVM_IOEVENTFD_FLAG_PIO,
> +        .fd = fd,
> +    };
> +    if (!assigned)
> +        kick.flags |= KVM_IOEVENTFD_FLAG_DEASSIGN;
> +    int r = kvm_vm_ioctl(kvm_state, KVM_IOEVENTFD,&kick);
> +    if (r<  0)
> +        return r;
> +    return 0;
> +}
>    

I think we really ought to try to avoid having global state used here.  
That means either we need to pass a CPUState to this function or we need 
to have a ioeventfd be allocated as a structure that is then passed 
around that can store a copy of the kvm_state fetched through CPUState.

I think the later is best.  We really don't want ioeventfd scattered 
throughout the code.

Regards,

Anthony Liguori