linux-kernel - Re: [PATCH 04/10] VFIO: pci: Add automasked field to vfio_pci_irq

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Date:   Wed, 31 May 2017 12:21:10 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        pbonzini@...hat.com, marc.zyngier@....com,
        christoffer.dall@...aro.org, drjones@...hat.com, wei@...hat.com
Subject: Re: [PATCH 04/10] VFIO: pci: Add automasked field to
 vfio_pci_irq_ctx

On Wed, 24 May 2017 22:13:17 +0200
Eric Auger <eric.auger@...hat.com> wrote:

> For direct EOI modality we will need to differentiate a userspace
> masking from the IRQ handler auto-masking.
> 
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>  drivers/vfio/pci/vfio_pci_intrs.c   | 15 +++++++++------
>  drivers/vfio/pci/vfio_pci_private.h |  1 +
>  2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index 1c46045..d4d377b 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -52,7 +52,7 @@ void vfio_pci_intx_mask(struct vfio_pci_device *vdev)
>  	if (unlikely(!is_intx(vdev))) {
>  		if (vdev->pci_2_3)
>  			pci_intx(pdev, 0);
> -	} else if (!vdev->ctx[0].masked) {
> +	} else if (!vdev->ctx[0].masked && !vdev->ctx[0].automasked) {
>  		/*
>  		 * Can't use check_and_mask here because we always want to
>  		 * mask, not just when something is pending.
> @@ -90,7 +90,8 @@ static int vfio_pci_intx_unmask_handler(void *opaque, void *unused)
>  	if (unlikely(!is_intx(vdev))) {
>  		if (vdev->pci_2_3)
>  			pci_intx(pdev, 1);
> -	} else if (vdev->ctx[0].masked && !vdev->virq_disabled) {
> +	} else if ((vdev->ctx[0].masked || vdev->ctx[0].automasked) &&
> +			!vdev->virq_disabled) {
>  		/*
>  		 * A pending interrupt here would immediately trigger,
>  		 * but we can avoid that overhead by just re-sending
> @@ -103,6 +104,7 @@ static int vfio_pci_intx_unmask_handler(void *opaque, void *unused)
>  			enable_irq(pdev->irq);
>  
>  		vdev->ctx[0].masked = (ret > 0);
> +		vdev->ctx[0].automasked = (ret > 0);
>  	}

This looks suspicious, if we leave this function with the interrupt
masked, isn't it due to an automask, not a usermask?

>  
>  	spin_unlock_irqrestore(&vdev->irqlock, flags);
> @@ -126,11 +128,12 @@ static irqreturn_t vfio_intx_handler(int irq, void *dev_id)
>  
>  	if (!vdev->pci_2_3) {
>  		disable_irq_nosync(vdev->pdev->irq);
> -		vdev->ctx[0].masked = true;
> +		vdev->ctx[0].automasked = true;
>  		ret = IRQ_HANDLED;
> -	} else if (!vdev->ctx[0].masked &&  /* may be shared */
> -		   pci_check_and_mask_intx(vdev->pdev)) {
> -		vdev->ctx[0].masked = true;
> +	} else if (!vdev->ctx[0].masked && !vdev->ctx[0].automasked &&
> +			pci_check_and_mask_intx(vdev->pdev)) {
> +		 /* shared INTx */
> +		vdev->ctx[0].automasked = true;
>  		ret = IRQ_HANDLED;
>  	}
>  
> diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
> index f561ac1..f7f1101 100644
> --- a/drivers/vfio/pci/vfio_pci_private.h
> +++ b/drivers/vfio/pci/vfio_pci_private.h
> @@ -35,6 +35,7 @@ struct vfio_pci_irq_ctx {
>  	struct virqfd		*mask;
>  	char			*name;
>  	bool			masked;
> +	bool			automasked;
>  	struct irq_bypass_producer	producer;
>  };
>