I attached the updated patch for those who want to try.
On Tue, Jun 05, 2007 at 01:08:07PM -0600, Alex Williamson wrote:
> Just to make sure I understand this DMA tracking... swiotlb only
> needs to track pages that that are accessed by the I/O device directly.
> The bounce buffer pool is presumably already pinned. This leaves only
> the individual mappings that don't use that pool, correct? With a
> hardware iommu the I/O device accesses unpinned memory whether it goes
> through the iommu address space or not. So all mappings need to be
> tracked. Correct?
It's same to my understanding.
> > @@ -1027,6 +1087,9 @@ void sba_unmap_single(struct device *dev
> > mark_clean(bus_to_virt(iova), size);
> > }
> > #endif
> > +#ifdef CONFIG_XEN
> > + gnttab_dma_unmap_page(iova);
>
> This interface can map multiple pages, so shouldn't we iterate
> through them?
Yeah. So Is the following part of the update patch necessary
independent of dma tracking?
@@ -1016,7 +1074,8 @@ void sba_unmap_single(struct device *dev
ASSERT(ioc);
#ifdef ALLOW_IOV_BYPASS
- if (likely((iova & ioc->imask) != ioc->ibase)) {
+ if (likely((iova & ioc->imask) != ioc->ibase) &&
+ !range_straddles_page_boundary(bus_to_virt(iova), size)) {
/*
** Address does not fall w/in IOVA, must be bypassing
*/
> I think the above should probably work, but I'm concerned about the
> overhead. We're adding one hypercall per scatterlist entry on the sg
> mapping path (we already have 2 virt to machine lookups on the map
> single path... not optimal). If we had the gnttab interface that didn't
> do it's own lookup, we might be able to put this in sba_io_pdir_entry()
> to avoid the extra hypercall. Thanks again for looking at this.
Agreed.
The grant table API should only mark/unmark that the page is under DMA,
thus we can reduce/optimise address conversion overhead.
--
yamahata
15173_2d56bb613bed_dma_tracking_sba_iommu_c.patch
Description: Text Data
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