From: Tianyu Lan <redacted>

In Hyper-V Isolation VM, swiotlb bnounce buffer size maybe 1G at most
and there maybe no enough memory from 0 to 4G according to memory layout.
Devices in Isolation VM can use memory above 4G as DMA memory and call
swiotlb_alloc_from_low_pages() to allocate swiotlb bounce buffer not
limit from 0 to 4G.

Signed-off-by: Tianyu Lan <redacted>
---
 arch/x86/kernel/cpu/mshyperv.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 5a99f993e639..50ba4622c650 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c

@@ -343,6 +343,7 @@ static void __init ms_hyperv_init_platform(void)
 		 * use swiotlb bounce buffer for dma transaction.
 		 */
 		swiotlb_force = SWIOTLB_FORCE;
+		swiotlb_set_alloc_from_low_pages(false);
 #endif
 	}
 

-- 
2.25.1