From: Tianyu Lan <Tianyu.Lan@microsoft.com>

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 allocates bounce buffer in the low end memory.
This patchset adds a new function swiotlb_set_alloc_from_low_pages()
to control swiotlb bounce buffer from low pages or no limitation.
Devices in Hyper-V Isolation VM may use memory above 4G as DMA memory
and switch swiotlb allocation in order to avoid no enough contiguous
memory in low pages.

Tianyu Lan (2):
  Swiotlb: Add swiotlb_alloc_from_low_pages switch
  x86/hyperv: Make swiotlb bounce buffer allocation not just from low
    pages

 arch/x86/kernel/cpu/mshyperv.c |  1 +
 include/linux/swiotlb.h        |  1 +
 kernel/dma/swiotlb.c           | 18 ++++++++++++++++--
 3 files changed, 18 insertions(+), 2 deletions(-)

-- 
2.25.1