On Thu, Jan 29, 2015 at 08:21:53PM +1100, Alexey Kardashevskiy wrote: > At the moment writing new TCE value to the IOMMU table fails with EBUSY > if there is a valid entry already. However PAPR specification allows > the guest to write new TCE value without clearing it first. > > Another problem this patch is addressing is the use of pool locks for > external IOMMU users such as VFIO. The pool locks are to protect > DMA page allocator rather than entries and since the host kernel does > not control what pages are in use, there is no point in pool locks and > exchange()+put_page(oldtce) is sufficient to avoid possible races. > > This adds an exchange() callback to iommu_table_ops which does the same > thing as set() plus it returns replaced TCE(s) so the caller can release > the pages afterwards. > > This implements exchange() for IODA2 only. This adds a requirement > for a platform to have exchange() implemented so from now on IODA2 is > the only supported PHB for VFIO-SPAPR. > > This replaces iommu_tce_build() and iommu_clear_tce() with > a single iommu_tce_xchg().
[snip] > @@ -294,8 +303,9 @@ static long tce_iommu_build(struct tce_container > *container, > > hva = (unsigned long) page_address(page) + > (tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK); > + oldtce = 0; > > - ret = iommu_tce_build(tbl, entry + 1, hva, direction); > + ret = iommu_tce_xchg(tbl, entry + i, hva, &oldtce, direction); Is the change from entry + 1 to entry + i here an actual bug fix? If so please mention it in the patch description. Paul. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
