[PATCH v9] dma-buf: Add ioctls to allow userspace to flush

[Chris Wilson]

On Mon, Feb 29, 2016 at 03:54:19PM +0100, Daniel Vetter wrote:
> On Thu, Feb 25, 2016 at 06:01:22PM +0000, Chris Wilson wrote:
> > On Thu, Feb 11, 2016 at 08:04:51PM -0200, Tiago Vignatti wrote:
> > > +static long dma_buf_ioctl(struct file *file,
> > > +			  unsigned int cmd, unsigned long arg)
> > > +{
> > > +	struct dma_buf *dmabuf;
> > > +	struct dma_buf_sync sync;
> > > +	enum dma_data_direction direction;
> > > +
> > > +	dmabuf = file->private_data;
> > > +
> > > +	switch (cmd) {
> > > +	case DMA_BUF_IOCTL_SYNC:
> > > +		if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
> > > +			return -EFAULT;
> > > +
> > > +		if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
> > > +			return -EINVAL;
> > > +
> > > +		switch (sync.flags & DMA_BUF_SYNC_RW) {
> > > +		case DMA_BUF_SYNC_READ:
> > > +			direction = DMA_FROM_DEVICE;
> > > +			break;
> > > +		case DMA_BUF_SYNC_WRITE:
> > > +			direction = DMA_TO_DEVICE;
> > > +			break;
> > > +		case DMA_BUF_SYNC_RW:
> > > +			direction = DMA_BIDIRECTIONAL;
> > > +			break;
> > > +		default:
> > > +			return -EINVAL;
> > > +		}
> > > +
> > > +		if (sync.flags & DMA_BUF_SYNC_END)
> > > +			dma_buf_end_cpu_access(dmabuf, direction);
> > > +		else
> > > +			dma_buf_begin_cpu_access(dmabuf, direction);
> > 
> > We forgot to report the error back to userspace. Might as well fixup the
> > callchain to propagate error from end-cpu-access as well. Found after
> > updating igt/gem_concurrent_blit to exercise dmabuf mmaps vs the GPU.
> 
> EINTR? Do we need to make this ABI - I guess so? Tiago, do you have
> patches? See drmIoctl() in libdrm for what's needed on the userspace side
> if my guess is right.

EINTR is the easiest, but conceivably we could also get EIO and
currently EAGAIN.

I am also seeing some strange timing dependent (i.e. valgrind doesn't
show up anything client side and the tests then pass) failures (SIGSEGV,
SIGBUS) with !llc.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre