RE: [PATCH 2/2] x86/hyperv: Set swiotlb_alloc_from_low_pages to false

[Michael Kelley (LINUX)]

From: Tianyu Lan <ltykernel@xxxxxxxxx> Sent: Wednesday, January 26, 2022 8:11 AM
> 
> 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. Set swiotlb_
> alloc_from_low_pages to false in Isolation VM.
> 
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
>  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..80a0423ac75d 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_alloc_from_low_pages = false;
>  #endif
>  	}
> 
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>