Re: [PATCH 03/14] x86: use dma-direct

From: Thomas Gleixner
Date: Thu Mar 15 2018 - 08:54:12 EST


On Thu, 15 Mar 2018, Christoph Hellwig wrote:

> On Thu, Mar 15, 2018 at 09:56:13AM +0100, Thomas Gleixner wrote:
> > On Wed, 14 Mar 2018, Christoph Hellwig wrote:
> >
> > > The generic dma-direct implementation is now functionally equivalent to
> > > the x86 nommu dma_map implementation, so switch over to using it.
> >
> > Can you please convert the various drivers first and then remove the
> > unused code?
>
> Which various drivers?
>
> > > Note that the various iommu drivers are switched from x86_dma_supported

The various iommu drivers ....

> > > to dma_direct_supported to provide identical functionality, although the
> > > checks looks fairly questionable for at least some of them.
> >
> > Can you please elaborate? From the above it's not clear which checks you
> > are referring to. If you convert these drivers seperately then explicit
> > information about your concerns wants to be in the changelogs.
>
> This bit:
>
> /* Copied from i386. Doesn't make much sense, because it will
> only work for pci_alloc_coherent.
> The caller just has to use GFP_DMA in this case. */
> if (mask < DMA_BIT_MASK(24))
> return 0;
>
> in x86_dma_supported, or the equivalent bit in dma_direct_supported.
> Kept for bug to bug compatibility, but I guess I should reword or
> just drop the changelog bit Ñf it causes confusion.

Reword please.

Thanks,

tglx