Device Coherent type uses device memory that is coherently accesible by
the CPU. This could be shown as SP (special purpose) memory range at the
BIOS-e820 memory enumeration. If no SP memory is supported in system,
this could be faked by setting CONFIG_EFI_FAKE_MEMMAP.
Currently, test_hmm only supports two different SP ranges of at least
256MB size. This could be specified in the kernel parameter variable
efi_fake_mem. Ex. Two SP ranges of 1GB starting at 0x100000000 &
0x140000000 physical address. Ex.
efi_fake_mem=1G@0x100000000:0x40000,1G@0x140000000:0x40000
Private and coherent device mirror instances can be created in the same
probed. This is done by passing the module parameters spm_addr_dev0 &
spm_addr_dev1. In this case, it will create four instances of
device_mirror. The first two correspond to private device type, the last
two to coherent type. Then, they can be easily accessed from user space
through /dev/hmm_mirror<num_device>. Usually num_device 0 and 1 are for
private, and 2 and 3 for coherent types. If no module parameters are
passed, two instances of private type device_mirror will be created only.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Alex Sierra <[email protected]>
Acked-by: Felix Kuehling <[email protected]>
Reviewed-by: Alistair Poppple <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Jerome Glisse <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Ralph Campbell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Alex Sierra
4c2e0f764e