linux-kernel - Re: [PATCH v3 04/10] VFIO: platform: add vfio_platform_set

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Date:	Mon, 17 Aug 2015 17:38:16 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Alex Williamson <alex.williamson@...hat.com>
CC:	eric.auger@...com, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	christoffer.dall@...aro.org, marc.zyngier@....com,
	feng.wu@...el.com, linux-kernel@...r.kernel.org,
	patches@...aro.org, pbonzini@...hat.com
Subject: Re: [PATCH v3 04/10] VFIO: platform: add vfio_platform_set_automasked

On 08/12/2015 08:56 PM, Alex Williamson wrote:
> On Mon, 2015-08-10 at 15:20 +0200, Eric Auger wrote:
>> This function makes possible to change the automasked mode.
>>
>> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>>
>> ---
>>
>> v1 -> v2:
>> - set forwarded flag
>> ---
>>  drivers/vfio/platform/vfio_platform_irq.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/drivers/vfio/platform/vfio_platform_irq.c b/drivers/vfio/platform/vfio_platform_irq.c
>> index b31b1f0..a285384 100644
>> --- a/drivers/vfio/platform/vfio_platform_irq.c
>> +++ b/drivers/vfio/platform/vfio_platform_irq.c
>> @@ -186,6 +186,25 @@ static irqreturn_t vfio_handler(int irq, void *dev_id)
>>  	return ret;
>>  }
>>  
>> +static int vfio_platform_set_automasked(struct vfio_platform_irq *irq,
>> +					   bool automasked)
>> +{
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&irq->lock, flags);
>> +	if (automasked) {
>> +		irq->forwarded = true;
>> +		irq->flags |= VFIO_IRQ_INFO_AUTOMASKED;
>> +		irq->handler = vfio_automasked_irq_handler;
>> +	} else {
>> +		irq->forwarded = false;
>> +		irq->flags &= ~VFIO_IRQ_INFO_AUTOMASKED;
>> +		irq->handler = vfio_irq_handler;
>> +	}
>> +	spin_unlock_irqrestore(&irq->lock, flags);
>> +	return 0;
> 
> In vfio-speak, automasked means level and we're not magically changing
> the IRQ from level to edge, we're simply able to handle level
> differently based on a hardware optimization.  Should the user visible
> flags therefore change based on this?  Aren't we really setting the
> forwarded state rather than the automasked state?

Well actually this was following the discussion we had a long time ago
about that topic:

http://lkml.iu.edu/hypermail/linux/kernel/1409.1/03659.html

I did not really know how to conclude ...

If it is preferred I can hide this to the userspace, no problem.

Eric


> 
>> +}
>> +
>>  static void vfio_platform_irq_bypass_stop(struct irq_bypass_producer *prod)
>>  {
>>  }
> 
> 
> 

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