Messages in this thread | | | Subject | Re: [PATCH RFC] swiotlb: Disable swiotlb overflow support when CONFIG_ISA is enabled | From | Shuah Khan <> | Date | Mon, 16 Jul 2012 09:48:20 -0600 |
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On Mon, 2012-07-16 at 10:45 -0400, Konrad Rzeszutek Wilk wrote: > On Thu, Jul 12, 2012 at 10:17:50AM -0600, Shuah Khan wrote: > > Disable iotlb overflow support when CONFIG_ISA is enabled. This is the > > first step towards removing overflow support, to be consistent with other > > iommu implementations and return DMA_ERROR_CODE. This disabling step is > > for finding drivers that don't call dma_mapping_error to check for errors > > returned by the mapping interface. Once drivers are fixed overflow support > > can be removed. > > I think I explained myself poorly. We don't want to break old drivers. > > If the old drivers expect this behavior (while they should be updated > to check the DMA), we need to retain this behavior. > > So I think the patch should be done the other way: > > Disable IOTLB overflow when CONFIG_ISA is disabled.
That makes lot of sense :) I will redo the patch. It might be good to a tunable to control enable/disable behavior. Even though support for this new tunable "swiotlb_overflow" projected to be short lived, it will be lot less painful to disable/enable as needed. Thought and comments?
> > But we also need to check whether there are other drivers > that don't properly check the DMA address. And if so, add them > to this list of must have enabled b/c you might be using this > driver.
Sound good. Again having a tunable would help in this case as well. > > The first goal is to figure out which of the drivers aren't doing this > properly. This should be possible by just grepping for 'dma_map' and > seeing which ones don't do the 'dma_check' right after.
I started some research into this and will continue and provide an update.
-- Shuah
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