From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id 7EA11DDEE6 for ; Tue, 8 Jan 2008 08:46:18 +1100 (EST) Subject: [PATCH][POWERPC] Workaround for iommu page alignment From: Benjamin Herrenschmidt To: Paul Mackerras Content-Type: text/plain Date: Tue, 08 Jan 2008 08:45:59 +1100 Message-Id: <1199742359.6734.14.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev list , Linux Kernel list Reply-To: benh@kernel.crashing.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Our iommu page size is currently always 4K. That means with our current code, drivers may do a dma_map_sg() of a 64K page and obtain a dma_addr_t that is only 4K aligned. This works fine in most cases except some infiniband HW it seems, where they tell the HW about the page size and it ignores the low bits of the DMA address. This works around it by making our IOMMU code enforce a PAGE_SIZE alignment for mappings of objects that are page aligned in the first place and whose size is larger or equal to a page. Signed-off-by: Benjamin Herrenschmidt --- Looks like it fell through the holiday cracks ... It could still go in 2.6.24 I suppose... If not, put it in 2.6.25 and we'll backport to stable later. Index: linux-work/arch/powerpc/kernel/iommu.c =================================================================== --- linux-work.orig/arch/powerpc/kernel/iommu.c 2007-12-21 10:39:39.000000000 +1100 +++ linux-work/arch/powerpc/kernel/iommu.c 2007-12-21 10:46:18.000000000 +1100 @@ -278,6 +278,7 @@ int iommu_map_sg(struct iommu_table *tbl unsigned long flags; struct scatterlist *s, *outs, *segstart; int outcount, incount, i; + unsigned int align; unsigned long handle; BUG_ON(direction == DMA_NONE); @@ -309,7 +310,11 @@ int iommu_map_sg(struct iommu_table *tbl /* Allocate iommu entries for that segment */ vaddr = (unsigned long) sg_virt(s); npages = iommu_num_pages(vaddr, slen); - entry = iommu_range_alloc(tbl, npages, &handle, mask >> IOMMU_PAGE_SHIFT, 0); + align = 0; + if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && (vaddr & ~PAGE_MASK) == 0) + align = PAGE_SHIFT - IOMMU_PAGE_SHIFT; + entry = iommu_range_alloc(tbl, npages, &handle, + mask >> IOMMU_PAGE_SHIFT, align); DBG(" - vaddr: %lx, size: %lx\n", vaddr, slen); @@ -572,7 +577,7 @@ dma_addr_t iommu_map_single(struct iommu { dma_addr_t dma_handle = DMA_ERROR_CODE; unsigned long uaddr; - unsigned int npages; + unsigned int npages, align; BUG_ON(direction == DMA_NONE); @@ -580,8 +585,13 @@ dma_addr_t iommu_map_single(struct iommu npages = iommu_num_pages(uaddr, size); if (tbl) { + align = 0; + if (IOMMU_PAGE_SHIFT < PAGE_SHIFT && + ((unsigned long)vaddr & ~PAGE_MASK) == 0) + align = PAGE_SHIFT - IOMMU_PAGE_SHIFT; + dma_handle = iommu_alloc(tbl, vaddr, npages, direction, - mask >> IOMMU_PAGE_SHIFT, 0); + mask >> IOMMU_PAGE_SHIFT, align); if (dma_handle == DMA_ERROR_CODE) { if (printk_ratelimit()) { printk(KERN_INFO "iommu_alloc failed, "