Re: For the problem when using swiotlb
From: Arnd Bergmann
Date: Mon Nov 17 2014 - 07:18:58 EST
On Monday 17 November 2014 19:56:27 Ding Tianhong wrote:
> Hi Catalin:
> The commit 3690951fc6d42f3a0903987677d0e592c49dd8db(arm64: Use swiotlb late initialisation)
> switches the DMA mapping code to swiotlb_tlb_late_init_with_default_size(), this will occur a problem
> when I run the scsi stress tests, the message as below:
> sas_controller b1000000.sas: swiotlb buffer is full (sz: 65536 bytes)..
> DMA: Out of SW-IOMMU space for 65536 bytes at device b1000000.sas
> The reason is that the swiotlb_tlb_late_init_with_default_size() could only alloc 16M memory for DMA-mapping,
> and the param in cmdline "swiotlb=xxx" is useless because the get_free_pages() only use the buddy to assigned a
> maximum memory of 16M(The MAX_ORDER is 13 for 4k pages), obviously 16M is too small in many scenes, but
> the swiotlb_init() which could reserved a bigger memory as wished could work well for most drivers.
> I could not get a better way to fix this problem except to revert this patch, so could you please give me some
> advise and help me, thanks very much.
In general, you should not need to use swiotlb for most devices, in
particular for high-performance devices like network or block.
Please make sure that you have set up the dma-ranges properties in
your DT properly to allow 64-bit DMA if the device supports it.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/