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

[Eric Auger <eric.auger@linaro.org>]

On 09/23/2015 09:28 PM, Alex Williamson wrote:
> 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,

Makes sense

Thanks

Eric
> 
> Alex
>