[Qemu-devel] Re: [RFC PATCH 19/20] Insert do_event_tap() to virtio-{blk, net}, comment out assert() on cpu_single_env temporally.

[Anthony Liguori <aliguori@linux.vnet.ibm.com>]

On 04/21/2010 12:57 AM, Yoshiaki Tamura wrote:
> do_event_tap() is inserted to functions which actually fire outputs.
> By synchronizing VMs before outputs are fired, we can failover to the
> receiver upon failure.  To save VM continuously, comment out assert()
> on cpu_single_env temporally.
>
> Signed-off-by: Yoshiaki Tamura<tamura.yoshiaki@lab.ntt.co.jp>
> ---
>   hw/virtio-blk.c |    2 ++
>   hw/virtio-net.c |    2 ++
>   qemu-kvm.c      |    7 ++++++-
>   3 files changed, 10 insertions(+), 1 deletions(-)
>    

This would be better done in the generic layers (the block and net 
layers respectively).  Then it would work with virtio and emulated devices.

Regards,

Anthony Liguori

> diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
> index b80402d..1dd1c31 100644
> --- a/hw/virtio-blk.c
> +++ b/hw/virtio-blk.c
> @@ -327,6 +327,8 @@ static void virtio_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
>           .old_bs = NULL,
>       };
>
> +    do_event_tap();
> +
>       while ((req = virtio_blk_get_request(s))) {
>           virtio_blk_handle_request(req,&mrb);
>       }
> diff --git a/hw/virtio-net.c b/hw/virtio-net.c
> index 5c0093e..1a32bf3 100644
> --- a/hw/virtio-net.c
> +++ b/hw/virtio-net.c
> @@ -667,6 +667,8 @@ static void virtio_net_handle_tx(VirtIODevice *vdev, VirtQueue *vq)
>   {
>       VirtIONet *n = to_virtio_net(vdev);
>
> +    do_event_tap();
> +
>       if (n->tx_timer_active) {
>           virtio_queue_set_notification(vq, 1);
>           qemu_del_timer(n->tx_timer);
> diff --git a/qemu-kvm.c b/qemu-kvm.c
> index 1414f49..769bc95 100644
> --- a/qemu-kvm.c
> +++ b/qemu-kvm.c
> @@ -935,8 +935,12 @@ int kvm_run(CPUState *env)
>
>       post_kvm_run(kvm, env);
>
> +    /* TODO: we need to prevent tapping events that derived from the
> +     * same VMEXIT. This needs more info from the kernel. */
>   #if defined(KVM_CAP_COALESCED_MMIO)
>       if (kvm_state->coalesced_mmio) {
> +        /* prevent from tapping events while handling coalesced_mmio */
> +        event_tap_suspend();
>           struct kvm_coalesced_mmio_ring *ring =
>               (void *) run + kvm_state->coalesced_mmio * PAGE_SIZE;
>           while (ring->first != ring->last) {
> @@ -946,6 +950,7 @@ int kvm_run(CPUState *env)
>               smp_wmb();
>               ring->first = (ring->first + 1) % KVM_COALESCED_MMIO_MAX;
>           }
> +        event_tap_resume();
>       }
>   #endif
>
> @@ -1770,7 +1775,7 @@ static void resume_all_threads(void)
>   {
>       CPUState *penv = first_cpu;
>
> -    assert(!cpu_single_env);
> +    /* assert(!cpu_single_env); */
>
>       while (penv) {
>           penv->stop = 0;
>