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authorDavid Woodhouse <David.Woodhouse@intel.com>2009-07-04 19:11:08 +0100
committerDavid Woodhouse <David.Woodhouse@intel.com>2009-07-04 19:19:10 +0100
commit3dfc813d94bba2046c6aed216e0fd69ac93a8e03 (patch)
tree227c2cecfdab3b9bb86508e9d8b6de51e68bfa70 /ipc
parent6941af2810c6fc970b88f7c0d52ba4e286acbee5 (diff)
intel-iommu: Don't use identity mapping for PCI devices behind bridges
Our current strategy for pass-through mode is to put all devices into the 1:1 domain at startup (which is before we know what their dma_mask will be), and only _later_ take them out of that domain, if it turns out that they really can't address all of memory. However, when there are a bunch of PCI devices behind a bridge, they all end up with the same source-id on their DMA transactions, and hence in the same IOMMU domain. This means that we _can't_ easily move them from the 1:1 domain into their own domain at runtime, because there might be DMA in-flight from their siblings. So we have to adjust our pass-through strategy: For PCI devices not on the root bus, and for the bridges which will take responsibility for their transactions, we have to start up _out_ of the 1:1 domain, just in case. This fixes the BUG() we see when we have 32-bit-capable devices behind a PCI-PCI bridge, and use the software identity mapping. It does mean that we might end up using 'normal' mapping mode for some devices which could actually live with the faster 1:1 mapping -- but this is only for PCI devices behind bridges, which presumably aren't the devices for which people are most concerned about performance. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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