From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> Hyper-V Isolation VM may fail to allocate swiotlb bounce buffer due to there is no enough contiguous memory from 0 to 4G in some cases. Current swiotlb code allocate bounce buffer in the low end memory. This patchset adds a switch "swiotlb_alloc_from_low_pages" and it's set to true by default. Platform may clear it if necessary. Devices in Hyper-V Isolation VM may use memory above 4G as DMA memory and set the switch to false in order to avoid no enough contiguous memory in low end address space. Tianyu Lan (2): Swiotlb: Add swiotlb_alloc_from_low_pages switch x86/hyperv: Set swiotlb_alloc_from_low_pages to false arch/x86/kernel/cpu/mshyperv.c | 1 + include/linux/swiotlb.h | 1 + kernel/dma/swiotlb.c | 13 +++++++++++-- 3 files changed, 13 insertions(+), 2 deletions(-) -- 2.25.1
