4.18-stable review patch. If anyone has any objections, please let me know.
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From: Christoph Hellwig hch@lst.de
commit 485734f3fc77c1eb77ffe138c027b9a4bf0178f3 upstream.
We already build the swiotlb code for 32-bit kernels with PAE support, but the code to actually use swiotlb has only been enabled for 64-bit kernels for an unknown reason.
Before Linux v4.18 we paper over this fact because the networking code, the SCSI layer and some random block drivers implemented their own bounce buffering scheme.
[ mingo: Changelog fixes. ]
Fixes: 21e07dba9fb1 ("scsi: reduce use of block bounce buffers") Fixes: ab74cfebafa3 ("net: remove the PCI_DMA_BUS_IS_PHYS check in illegal_highdma") Reported-by: Matthew Whitehead tedheadster@gmail.com Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Thomas Gleixner tglx@linutronix.de Tested-by: Matthew Whitehead tedheadster@gmail.com Cc: konrad.wilk@oracle.com Cc: iommu@lists.linux-foundation.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20181014075208.2715-1-hch@lst.de Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/pci-swiotlb.c | 2 -- 1 file changed, 2 deletions(-)
--- a/arch/x86/kernel/pci-swiotlb.c +++ b/arch/x86/kernel/pci-swiotlb.c @@ -42,10 +42,8 @@ IOMMU_INIT_FINISH(pci_swiotlb_detect_ove 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