54fc3c681d
Unlike normal memory ("memory" compatible type in the FDT), the
persistent memory ("ibm,pmemory" in the FDT) can be mapped anywhere in
the guest physical space and it can be used for DMA.
In order to maintain 1:1 mapping via the huge DMA window, we need to
know the maximum physical address at the time of the window setup. So
far we've been looking at "memory" nodes but "ibm,pmemory" does not
have fixed addresses and the persistent memory may be mapped
afterwards.
Since the persistent memory is still backed with page structs, use
MAX_PHYSMEM_BITS as the upper limit.
This effectively disables huge DMA window in LPAR under pHyp if
persistent memory is present but this is the best we can do for the
moment.
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Wen Xiong<wenxiong@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200331012338.23773-1-aik@ozlabs.ru
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.