On Fri, May 29, 2015 at 06:44:47PM +1000, 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 and DMA direction so > the caller can release the pages afterwards. The exchange() receives > a physical address unlike set() which receives linear mapping address; > and returns a physical address as the clear() does. > > This implements exchange() for P5IOC2/IODA/IODA2. This adds a requirement > for a platform to have exchange() implemented in order to support VFIO. > > This replaces iommu_tce_build() and iommu_clear_tce() with > a single iommu_tce_xchg(). > > This makes sure that TCE permission bits are not set in TCE passed to > IOMMU API as those are to be calculated by platform code from > DMA direction. > > This moves SetPageDirty() to the IOMMU code to make it work for both > VFIO ioctl interface in in-kernel TCE acceleration (when it becomes > available later). > > Signed-off-by: Alexey Kardashevskiy <aik@xxxxxxxxx> > [aw: for the vfio related changes] > Acked-by: Alex Williamson <alex.williamson@xxxxxxxxxx> Reviewed-by: David Gibson <david@xxxxxxxxxxxxxxxxxxxxx> -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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