Re: [PATCH] DMA 4GB boundary protection
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2007-03-27 20:55:47
On Tue, 2007-03-27 at 15:10 -0500, Jake Moilanen wrote:
I just had to realign the start_index in case it didn't start at a 4GB boundary. Other than that, it worked like a champ. I also changed to forloop to exit if it's the last entry. Signed-off-by: Jake Moilanen <redacted>
patch got mangled ...
quoted hunk ↗ jump to hunk
--- arch/powerpc/kernel/iommu.c | 35 ++++++++++++++++++++++++++++++++++- 1 files changed, 34 insertions(+), 1 deletion(-) Index: powerpc/arch/powerpc/kernel/iommu.c ===================================================================--- powerpc.orig/arch/powerpc/kernel/iommu.c +++ powerpc/arch/powerpc/kernel/iommu.c@@ -47,6 +47,8 @@ static int novmerge = 0; static int novmerge = 1; #endif +static int protect4gb = 1; + static inline unsigned long iommu_num_pages(unsigned long vaddr, unsigned long slen) {@@ -58,6 +60,16 @@ static inline unsigned long iommu_num_pa return npages; } +static int __init setup_protect4gb(char *str) +{ + if (strcmp(str, "on") == 0) + protect4gb = 1; + else if (strcmp(str, "off") == 0) + protect4gb = 0; + + return 1; +} + static int __init setup_iommu(char *str) { if (!strcmp(str, "novmerge"))@@ -67,6 +79,7 @@ static int __init setup_iommu(char *str) return 1; } +__setup("protect4gb=", setup_protect4gb); __setup("iommu=", setup_iommu); static unsigned long iommu_range_alloc(struct iommu_table *tbl,@@ -429,6 +442,9 @@ void iommu_unmap_sg(struct iommu_table * 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;@@ -450,7 +466,7 @@ struct iommu_table *iommu_init_table(str #ifdef CONFIG_CRASH_DUMP if (ppc_md.tce_get) { - unsigned long index, tceval; + unsigned long tceval; unsigned long tcecount = 0; /*@@ -480,6 +496,23 @@ struct iommu_table *iommu_init_table(str 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 << IOMMU_PAGE_SHIFT) >> 32; + start_index |= (entries_per_4g - 1); + + end_index = tbl->it_offset + 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"); _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev