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SubjectRe: [PATCH] x86: enable swiotlb for > 4GiG ram on 32-bit kernels
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On 10/14/18 3:52 AM, Christoph Hellwig wrote:
> We already build the swiotlb code for 32b-t kernels with PAE support,
> but the code to actually use swiotlb has only been enabled for 64-bit
> kernel for an unknown reason.
>
> Before Linux 4.18 we papers over this fact because the networking code,
> the scsi layer and some random block drivers implenented their own
> bounce buffering scheme.
>
> Fixes: 21e07dba ("scsi: reduce use of block bounce buffers")
> Fixes: ab74cfeb ("net: remove the PCI_DMA_BUS_IS_PHYS check in illegal_highdma")
> Reported-by: tedheadster <tedheadster@gmail.com>
> Tested-by: tedheadster <tedheadster@gmail.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

But since it is already in 'tip' feel free to ignore my tag.

Thanks!
> ---
> arch/x86/kernel/pci-swiotlb.c | 2 --
> 1 file changed, 2 deletions(-)
>
> diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
> index 661583662430..71c0b01d93b1 100644
> --- a/arch/x86/kernel/pci-swiotlb.c
> +++ b/arch/x86/kernel/pci-swiotlb.c
> @@ -42,10 +42,8 @@ IOMMU_INIT_FINISH(pci_swiotlb_detect_override,
> int __init pci_swiotlb_detect_4gb(void)
> {
> /* don't initialize swiotlb if iommu=off (no_iommu=1) */
> -#ifdef CONFIG_X86_64
> if (!no_iommu && max_possible_pfn > MAX_DMA32_PFN)
> swiotlb = 1;
> -#endif
>
> /*
> * If SME is active then swiotlb will be set to 1 so that bounce
>

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