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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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201ed7f327
At the moment we create a small window only for 32bit devices, the window maps 0..2GB of the PCI space only. For other devices we either use a sketchy bypass or hardware bypass but the former can only work if the amount of RAM is no bigger than the device's DMA mask and the latter requires devices to support at least 59bit DMA. This extends the default DMA window to the maximum size possible to allow a wider DMA mask than just 32bit. The default window size is now limited by the the iommu_table::it_map allocation bitmap which is a contiguous array, 1 bit per an IOMMU page. This increases the default IOMMU page size from hard coded 4K to the system page size to allow wider DMA masks. This increases the level number to not exceed the max order allocation limit per TCE level. By the same time, this keeps minimal levels number as 2 in order to save memory. As the extended window now overlaps the 32bit MMIO region, this adds an area reservation to iommu_init_table(). After this change the default window size is 0x80000000000==1<<43 so devices limited to DMA mask smaller than the amount of system RAM can still use more than just 2GB of memory for DMA. This is an optimization and not a bug fix for DMA API usage. With the on-demand allocation of indirect TCE table levels enabled and 2 levels, the first TCE level size is just 1<<ceil((log2(0x7ffffffffff+1)-16)/2)=16384 TCEs or 2 system pages. Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20190718051139.74787-5-aik@ozlabs.ru |
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