Re: [Qemu-devel] [PATCH 2/2] hw/vfio/platform: do not set resamplefd for edge-sensitive IRQS

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 2015-09-23 at 00:00 +0100, Eric Auger wrote:
> In irqfd mode, current code attempts to set a resamplefd whatever
> the type of the IRQ. For an edge-sensitive IRQ this attempt fails
> and as a consequence the whole irqfd setup fails and we fall back
> to the slow mode. This patch bypasses the resamplefd setting for
> non level-sentive IRQs.
> 
> Signed-off-by: Eric Auger <eric.auger@linaro.org>
> ---
>  hw/vfio/platform.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/hw/vfio/platform.c b/hw/vfio/platform.c
> index 38eaccf..2c91650 100644
> --- a/hw/vfio/platform.c
> +++ b/hw/vfio/platform.c
> @@ -352,6 +352,10 @@ static int vfio_set_resample_eventfd(VFIOINTp *intp)
>      int argsz, ret;
>      int32_t *pfd;
>  
> +    if (!(intp->flags & VFIO_IRQ_INFO_AUTOMASKED)) {
> +        return 0;
> +    }
> +
>      argsz = sizeof(*irq_set) + sizeof(*pfd);
>      irq_set = g_malloc0(argsz);
>      irq_set->argsz = argsz;

Aren't we also wasting a file descriptor for intp->unmask on edge IRQs
as well?  I'd be tempted to make a helper function that does this test
and use it both to avoid calling this in vfio_start_irqfd_injection()
and also to avoid creating the unused eventfd in vfio_init_intp().
Thanks,

Alex