From 0d8c8094cc48350a9cb870b4b59c700322960c15 Mon Sep 17 00:00:00 2001 From: Alexey Kardashevskiy Date: Tue, 8 Sep 2020 11:51:06 +1000 Subject: [PATCH] powerpc/dma: Fix dma_map_ops::get_required_mask There are 2 problems with it: 1. "<" vs expected "<<" 2. the shift number is an IOMMU page number mask, not an address mask as the IOMMU page shift is missing. This did not hit us before 7f65559feadd ("powerpc: use the generic dma_ops_bypass mode") because we had additional code to handle bypass mask so this chunk (almost?) never executed.However there were reports that aacraid does not work with "iommu=nobypass". After 7f65559feadd, aacraid (and probably others which call dma_get_required_mask() before setting the mask) was unable to enable 64bit DMA and fall back to using IOMMU which was known not to work, one of the problems is double free of an IOMMU page. This fixes DMA for aacraid, both with and without "iommu=nobypass" in the kernel command line. Verified with "stress-ng -d 4". Fixes: 1b26dc7abedc ("powerpc: Override dma_get_required_mask by platform hook and ops") Cc: stable@vger.kernel.org # v3.2+ Signed-off-by: Alexey Kardashevskiy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200908015106.79661-1-aik@ozlabs.ru --- arch/powerpc/kernel/dma-iommu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c index 569fecd7b5b23..9053fc9d20c72 100644 --- a/arch/powerpc/kernel/dma-iommu.c +++ b/arch/powerpc/kernel/dma-iommu.c @@ -120,7 +120,8 @@ u64 dma_iommu_get_required_mask(struct device *dev) if (!tbl) return 0; - mask = 1ULL < (fls_long(tbl->it_offset + tbl->it_size) - 1); + mask = 1ULL << (fls_long(tbl->it_offset + tbl->it_size) + + tbl->it_page_shift - 1); mask += mask - 1; return mask; -- 2.39.5