On Mon, 2011-11-14 at 13:54 -0700, Alex Williamson wrote:
> On Fri, 2011-11-11 at 18:14 -0600, Scott Wood wrote:
> > On 11/03/2011 03:12 PM, Alex Williamson wrote:
> > > + for (i = 0; i < npage; i++, iova += PAGE_SIZE, vaddr += PAGE_SIZE) {
> > > + unsigned long pfn = 0;
> > > +
> > > + ret = vaddr_get_pfn(vaddr, rdwr, &pfn);
> > > + if (ret) {
> > > + __vfio_dma_unmap(iommu, start, i, rdwr);
> > > + return ret;
> > > + }
> > > +
> > > + /* Only add actual locked pages to accounting */
> > > + if (!is_invalid_reserved_pfn(pfn))
> > > + locked++;
> > > +
> > > + ret = iommu_map(iommu->domain, iova,
> > > + (phys_addr_t)pfn << PAGE_SHIFT, 0, prot);
> > > + if (ret) {
> > > + /* Back out mappings on error */
> > > + put_pfn(pfn, rdwr);
> > > + __vfio_dma_unmap(iommu, start, i, rdwr);
> > > + return ret;
> > > + }
> > > + }
> >
> > There's no way to hand this stuff to the IOMMU driver in chunks larger
> > than a page? That's going to be a problem for our IOMMU, which wants to
> > deal with large windows.
>
> There is, this is just a simple implementation that maps individual
> pages. We "just" need to determine physically contiguous chunks and
> mlock them instead of using get_user_pages. The current implementation
> is much like how KVM maps iommu pages, but there shouldn't be a user API
> change to try to use larger chinks. We want this for IOMMU large page
> support too.
Also, at one point intel-iommu didn't allow sub-ranges to be unmapped;
an unmap of a single page would unmap the entire original mapping that
contained that page. That made it easier to map each page individually
for the flexibility it provided on unmap. I need to see if we still
have that restriction. Thanks,
Alex
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