iommu sg: powerpc: remove DMA 4GB boundary protection (383af952) · Commits · 戴 / test

Previously, during initialization of the IOMMU tables, the last entry at each 4GB boundary is marked as used since there are many adapters which cannot handle DMAing across any 4GB boundary. The IOMMU doesn't allocate a memory area spanning LLD's segment boundary anymore. The segment boundary of devices are set to 4GB by default. So we can remove 4GB boundary protection now. Signed-off-by:

FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Jeff Garzik <jeff@garzik.org> Cc: James Bottomley <James.Bottomley@steeleye.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

arch/powerpc/kernel/iommu.c

+1 −20

Original line number	Diff line number	Diff line
		@@ -453,9 +453,6 @@ void iommu_unmap_sg(struct iommu_table tbl, struct scatterlist sglist,
		struct iommu_table iommu_init_table(struct iommu_table tbl, int nid)
		{
		unsigned long sz;
		unsigned long start_index, end_index;
		unsigned long entries_per_4g;
		unsigned long index;
		static int welcomed = 0;
		struct page *page;

		@@ -477,6 +474,7 @@ struct iommu_table iommu_init_table(struct iommu_table tbl, int nid)

		#ifdef CONFIG_CRASH_DUMP
		if (ppc_md.tce_get) {
		unsigned long index;
		unsigned long tceval;
		unsigned long tcecount = 0;

		@@ -507,23 +505,6 @@ struct iommu_table iommu_init_table(struct iommu_table tbl, int nid)
		ppc_md.tce_free(tbl, tbl->it_offset, tbl->it_size);
		#endif

		/*
		* DMA cannot cross 4 GB boundary. Mark last entry of each 4
		* GB chunk as reserved.
		*/
		if (protect4gb) {
		entries_per_4g = 0x100000000l >> IOMMU_PAGE_SHIFT;

		/* Mark the last bit before a 4GB boundary as used */
		start_index = tbl->it_offset \| (entries_per_4g - 1);
		start_index -= tbl->it_offset;

		end_index = tbl->it_size;

		for (index = start_index; index < end_index - 1; index += entries_per_4g)
		__set_bit(index, tbl->it_map);
		}

		if (!welcomed) {
		printk(KERN_INFO "IOMMU table initialized, virtual merging %s\n",
		novmerge ? "disabled" : "enabled");

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