powerpc/iommu: Add ppc_md.tce_get() callback for use by VFIO

The upcoming VFIO support requires a way to know which
entry in the TCE map is not empty in order to do cleanup
at QEMU exit/crash. This patch adds such functionality
to POWERNV platform code.

Signed-off-by: Alexey Kardashevskiy <[e-mail]>
Signed-off-by: Benjamin Herrenschmidt <[e-mail]>

arch/powerpc/platforms/powernv/pci.c

···
 		pnv_tce_invalidate(tbl, tces, tcep - 1);
 }
 
+static unsigned long pnv_tce_get(struct iommu_table *tbl, long index)
+{
+	return ((u64 *)tbl->it_base)[index - tbl->it_offset];
+}
+
 void pnv_pci_setup_iommu_table(struct iommu_table *tbl,
 			       void *tce_mem, u64 tce_size,
 			       u64 dma_offset)
···
 	ppc_md.pci_dma_dev_setup = pnv_pci_dma_dev_setup;
 	ppc_md.tce_build = pnv_tce_build;
 	ppc_md.tce_free = pnv_tce_free;
+	ppc_md.tce_get = pnv_tce_get;
 	ppc_md.pci_probe_mode = pnv_pci_probe_mode;
 	set_pci_dma_ops(&dma_iommu_ops);