[Intel-gfx] [RESEND PATCH 1/3] drm/i915/dmabuf: Implement pwrite() callback

[Janusz Krzysztofik]

Hi Daniel,

On Tuesday, November 5, 2019 3:27:55 PM CET Daniel Vetter wrote:
> On Thu, Oct 31, 2019 at 09:29:56AM +0100, Janusz Krzysztofik wrote:
> > We need dmabuf specific pwrite() callback utilizing dma-buf API,
> > otherwise GEM_PWRITE IOCTL will no longer work with dma-buf backed
> > (i.e., PRIME imported) objects on hardware with no mappable aperture.
> > 
> > Signed-off-by: Janusz Krzysztofik <janusz.krzysztofik at linux.intel.com>
> > Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> > Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> 
> Do we have userspace for this (aside from igts)? Specifically for the
> gen12 + dma-buf import + pwrite/read/whatever case you're fixing in this
> series here.

I don't know the answer, sorry, I can only tell that prime_vgem IGT test uses 
gem_read()/gem_write(), which call I915_GEM_PREAD/I915_GEM_PWRITE DRM IOCTLs 
respectively, on PRIME imported vgem objects.

Thanks,
Janusz


> -Daniel
> 
> > ---
> >  drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c | 55 ++++++++++++++++++++++
> >  1 file changed, 55 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > index 96ce95c8ac5a..93eea1031c82 100644
> > --- a/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > +++ b/drivers/gpu/drm/i915/gem/i915_gem_dmabuf.c
> > @@ -248,9 +248,64 @@ static void i915_gem_object_put_pages_dmabuf(struct drm_i915_gem_object *obj,
> >  				 DMA_BIDIRECTIONAL);
> >  }
> >  
> > +static int i915_gem_object_pwrite_dmabuf(struct drm_i915_gem_object *obj,
> > +					 const struct drm_i915_gem_pwrite *args)
> > +{
> > +	struct dma_buf *dmabuf = obj->base.import_attach->dmabuf;
> > +	void __user *user_data = u64_to_user_ptr(args->data_ptr);
> > +	struct file *file = dmabuf->file;
> > +	const struct file_operations *fop = file->f_op;
> > +	void __force *vaddr;
> > +	int ret;
> > +
> > +	if (fop->write) {
> > +		loff_t offset = args->offset;
> > +
> > +		/*
> > +		 * fop->write() is supposed to call dma_buf_begin_cpu_access()
> > +		 * if O_SYNC flag is set, avoid calling it twice
> > +		 */
> > +		if (!(file->f_flags & O_SYNC)) {
> > +			ret = dma_buf_begin_cpu_access(dmabuf, DMA_TO_DEVICE);
> > +			if (ret)
> > +				return ret;
> > +		}
> > +
> > +		ret = fop->write(file, user_data, args->size, &offset);
> > +
> > +		if (!(file->f_flags & O_SYNC))
> > +			dma_buf_end_cpu_access(dmabuf, DMA_TO_DEVICE);
> > +
> > +		if (!ret)
> > +			return 0;
> > +	}
> > +
> > +	/* dma-buf file .write() not supported or failed, try dma_buf_vmap() */
> > +	ret = dma_buf_begin_cpu_access(dmabuf, DMA_TO_DEVICE);
> > +	if (ret)
> > +		return ret;
> > +
> > +	vaddr = dma_buf_vmap(dmabuf);
> > +	if (!vaddr)
> > +		goto out_err;
> > +
> > +	ret = copy_from_user(vaddr + args->offset, user_data, args->size);
> > +	dma_buf_vunmap(dmabuf, vaddr);
> > +	if (!ret)
> > +		goto out_end;
> > +
> > +out_err:
> > +	/* fall back to GTT mapping */
> > +	ret = -ENODEV;
> > +out_end:
> > +	dma_buf_end_cpu_access(dmabuf, DMA_TO_DEVICE);
> > +	return ret;
> > +}
> > +
> >  static const struct drm_i915_gem_object_ops i915_gem_object_dmabuf_ops = {
> >  	.get_pages = i915_gem_object_get_pages_dmabuf,
> >  	.put_pages = i915_gem_object_put_pages_dmabuf,
> > +	.pwrite = i915_gem_object_pwrite_dmabuf,
> >  };
> >  
> >  struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
> 
>