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authorDavid Gibson <david@gibson.dropbear.id.au>2012-06-27 14:50:38 +1000
committerAnthony Liguori <aliguori@us.ibm.com>2012-06-27 16:33:25 -0500
commitd86a77f8abb9ed4b598f86f6476ccb2dc0a433e6 (patch)
tree671c75b619e9a2ec1a09c7099befbaf9d1192df1 /input.c
parent8292f75ad2d65364387b09bb920dd65c8842a3a6 (diff)
iommu: Add universal DMA helper functions
Not that long ago, every device implementation using DMA directly accessed guest memory using cpu_physical_memory_*(). This meant that adding support for a guest visible IOMMU would require changing every one of these devices to go through IOMMU translation. Shortly before qemu 1.0, I made a start on fixing this by providing helper functions for PCI DMA. These are currently just stubs which call the direct access functions, but mean that an IOMMU can be implemented in one place, rather than for every PCI device. Clearly, this doesn't help for non PCI devices, which could also be IOMMU translated on some platforms. It is also problematic for the devices which have both PCI and non-PCI version (e.g. OHCI, AHCI) - we cannot use the the pci_dma_*() functions, because they assume the presence of a PCIDevice, but we don't want to have to check between pci_dma_*() and cpu_physical_memory_*() every time we do a DMA in the device code. This patch makes the first step on addressing both these problems, by introducing new (stub) dma helper functions which can be used for any DMA capable device. These dma functions take a DMAContext *, a new (currently empty) variable describing the DMA address space in which the operation is to take place. NULL indicates untranslated DMA directly into guest physical address space. The intention is that in future non-NULL values will given information about any necessary IOMMU translation. DMA using devices must obtain a DMAContext (or, potentially, contexts) from their bus or platform. For now this patch just converts the PCI wrappers to be implemented in terms of the universal wrappers, converting other drivers can take place over time. Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro> Cc: Richard Henderson <rth@twiddle.net> Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
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