af9d00e93a
To enable memory unplug without splitting kernel page table
mapping, we force the max mapping size to the LMB size. LMB
size is the unit in which hypervisor will do memory add/remove
operation.
Pseries systems supports max LMB size of 256MB. Hence on pseries,
we now end up mapping memory with 2M page size instead of 1G. To improve
that we want hypervisor to hint the kernel about the hotplug
memory range. That was added that as part of
commit b6eca183e23e ("powerpc/kernel: Enables memory
hot-remove after reboot on pseries guests")
But PowerVM doesn't provide that hint yet. Once we get PowerVM
updated, we can then force the 2M mapping only to hot-pluggable
memory region using memblock_is_hotpluggable(). Till then
let's depend on LMB size for finding the mapping page size
for linear range.
With this change KVM guest will also be doing linear mapping with
2M page size.
The actual TLB benefit of mapping guest page table entries with
hugepage size can only be materialized if the partition scoped
entries are also using the same or higher page size. A guest using
1G hugetlbfs backing guest memory can have a performance impact with
the above change.
Signed-off-by: Bharata B Rao <bharata@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
[mpe: Fold in fix from Aneesh spotted by lkp@intel.com]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200709131925.922266-5-aneesh.kumar@linux.ibm.com
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.