linux-kernel - Re: [RFC 1/5] drm/virtio: add virtio_gpu_alloc

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Date:   Tue, 13 Dec 2016 09:53:09 -0200
From:   Gustavo Padovan <gustavo@...ovan.org>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, robdclark@...il.com,
        Gustavo Padovan <gustavo.padovan@...labora.co.uk>,
        David Airlie <airlied@...ux.ie>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [RFC 1/5] drm/virtio: add virtio_gpu_alloc_fence()

2016-12-13 Gerd Hoffmann <kraxel@...hat.com>:

>   Hi,
> 
> > +struct virtio_gpu_fence *virtio_gpu_fence_alloc(struct virtio_gpu_device *vgdev)
> > +{
> > +	struct virtio_gpu_fence_driver *drv = &vgdev->fence_drv;
> > +	struct virtio_gpu_fence *fence;
> > +	unsigned long irq_flags;
> > +
> > +	fence = kmalloc(sizeof(struct virtio_gpu_fence), GFP_ATOMIC);
> > +	if (!fence)
> > +		return NULL;
> > +
> 
> > +	spin_lock_irqsave(&drv->lock, irq_flags);
> > +	fence->drv = drv;
> > +	fence->seq = ++drv->sync_seq;
> > +	dma_fence_init(&fence->f, &virtio_fence_ops, &drv->lock,
> > +		       drv->context, fence->seq);
> > +	spin_unlock_irqrestore(&drv->lock, irq_flags);
> 
> seq assignment ...
> 
> > +
> > +	return fence;
> > +}
> > +
> >  int virtio_gpu_fence_emit(struct virtio_gpu_device *vgdev,
> >  			  struct virtio_gpu_ctrl_hdr *cmd_hdr,
> > -			  struct virtio_gpu_fence **fence)
> > +			  struct virtio_gpu_fence *fence)
> >  {
> >  	struct virtio_gpu_fence_driver *drv = &vgdev->fence_drv;
> >  	unsigned long irq_flags;
> >  
> > -	*fence = kmalloc(sizeof(struct virtio_gpu_fence), GFP_ATOMIC);
> > -	if ((*fence) == NULL)
> > -		return -ENOMEM;
> > -
> >  	spin_lock_irqsave(&drv->lock, irq_flags);
> > -	(*fence)->drv = drv;
> > -	(*fence)->seq = ++drv->sync_seq;
> > -	dma_fence_init(&(*fence)->f, &virtio_fence_ops, &drv->lock,
> > -		       drv->context, (*fence)->seq);
> 
> ... must stay here.  Otherwise requests can be submitted to the virt
> queue with fence sequence numbers out of order.

Yes, makes sense. So I'll just leave the kmalloc in there.

Gustavo