Some devices (e.g. xHCI USB host controllers) may require the use of
large areas of host memory for private use by the device. These
allocations cannot be satisfied from iPXE's limited heap space, and so
are currently allocated using umalloc() which will allocate external
system memory (and alter the system memory map as needed).
Provide dma_umalloc() to provide such allocations as part of the DMA
API, since there is otherwise no way to guarantee that the allocated
regions are usable for coherent DMA.
Signed-off-by: Michael Brown <mcb30@ipxe.org>
6e01b74a8a