Re: [LKML] Re: [PATCH] swiotlb v0.6: seperation of physical/virtual address translation

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

> > Since the last posting I've:
> >  - Made the exported functions/variables have the 'swiotlb_bk' prefix instead
> >    of the 'do_[map|unmap]*' and 'io_tlb_*' combination.
> 
> Why can't we use more simpler names such as 'swiotlb_tbl_index'?

Much better. I was trying to come up with a name and the one I came up
with was 'bookkeeping', which I shortned to 'bk'. But 'tbl'
sounds better.

> Why do we need to add the prefix to static things like
> 'swiotlb_bk_list', 'swiotlb_bk_index', etc? Please let them alone.

Yup. Removed.
> > I had not addressed the question of removing the 'overflow' buffer. There are over
> > ~300 instances of the the DMA operations not being checked which plan on addressing
> > in a seperate set of patches that will slowly roll out the checks and then
> > finally the removal of the 'overflow' buffer.
> 
> Except for swiotlb, no IOMMU implementations has the mechanism of

I believe the GART one does it too. I think the overflow points to the
first page of the GART address and has logic to remind the user that danger
is immenient.

> overflow buffer. So drivers that don't check a DMA mapping error are
> broken anyway. Also the size of the overflow is 32K by default. We
> often see larger request than that. Even with the overflow mechanism,
> we see data corruption anyway.