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Aneesh Kumar K.V baed68a953 powerpc/hugetlb: Don't do runtime allocation of 16G pages in LPAR configuration 
commit 35f2806b48 upstream.

We added runtime allocation of 16G pages in commit 4ae279c2c9
("powerpc/mm/hugetlb: Allow runtime allocation of 16G.") That was done
to enable 16G allocation on PowerNV and KVM config. In case of KVM
config, we mostly would have the entire guest RAM backed by 16G
hugetlb pages for this to work. PAPR do support partial backing of
guest RAM with hugepages via ibm,expected#pages node of memory node in
the device tree. This means rest of the guest RAM won't be backed by
16G contiguous pages in the host and hence a hash page table insertion
can fail in such case.

An example error message will look like

  hash-mmu: mm: Hashing failure ! EA=0x7efc00000000 access=0x8000000000000006 current=readback
  hash-mmu:     trap=0x300 vsid=0x67af789 ssize=1 base psize=14 psize 14 pte=0xc000000400000386
  readback[12260]: unhandled signal 7 at 00007efc00000000 nip 00000000100012d0 lr 000000001000127c code 2

This patch address that by preventing runtime allocation of 16G
hugepages in LPAR config. To allocate 16G hugetlb one need to kernel
command line hugepagesz=16G hugepages=<number of 16G pages>

With radix translation mode we don't run into this issue.

This change will prevent runtime allocation of 16G hugetlb pages on
kvm with hash translation mode. However, with the current upstream it
was observed that 16G hugetlbfs backed guest doesn't boot at all.

We observe boot failure with the below message:
  [131354.647546] KVM: map_vrma at 0 failed, ret=-4

That means this patch is not resulting in an observable regression.
Once we fix the boot issue with 16G hugetlb backed memory, we need to
use ibm,expected#pages memory node attribute to indicate 16G page
reservation to the guest. This will also enable partial backing of
guest RAM with 16G pages.

Fixes: 4ae279c2c9 ("powerpc/mm/hugetlb: Allow runtime allocation of 16G.")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-03-23 20:10:08 +01:00
arch powerpc/hugetlb: Don't do runtime allocation of 16G pages in LPAR configuration 2019-03-23 20:10:08 +01:00
block blk-mq: insert rq with DONTPREP to hctx dispatch list when requeue 2019-03-23 20:09:45 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: testmgr - skip crc32c context test for ahash algorithms 2019-03-23 20:09:55 +01:00
Documentation clocksource/drivers/arch_timer: Workaround for Allwinner A64 timer instability 2019-03-23 20:09:58 +01:00
drivers serial: 8250_pci: Have ACCES cards that use the four port Pericom PI7C9X7954 chip use the pci_pericom_setup() 2019-03-23 20:10:06 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs jbd2: fix compile warning when using JBUFFER_TRACE 2019-03-23 20:10:06 +01:00
include bpf: only test gso type on gso packets 2019-03-23 20:10:06 +01:00
init Revert "mm: use early_pfn_to_nid in page_ext_init" 2019-03-23 20:09:46 +01:00
ipc ipc/shm.c: use ERR_CAST() for shm_lock() error return 2018-10-05 16:32:04 -07:00
kernel kernel/sysctl.c: add missing range check in do_proc_dointvec_minmax_conv 2019-03-23 20:10:04 +01:00
lib assoc_array: Fix shortcut creation 2019-03-23 20:09:48 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/memory.c: do_fault: avoid usage of stale vm_area_struct 2019-03-23 20:10:04 +01:00
net bpf: only test gso type on gso packets 2019-03-23 20:10:06 +01:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-02-15 08:10:11 +01:00
scripts kallsyms: Handle too long symbols in kallsyms.c 2019-03-23 20:09:47 +01:00
security security/selinux: fix SECURITY_LSM_NATIVE_LABELS on reused superblock 2019-03-23 20:10:06 +01:00
sound ASoC: topology: free created components in tplg load error 2019-03-23 20:09:50 +01:00
tools selftests: fib_tests: sleep after changing carrier. again. 2019-03-23 20:09:52 +01:00
usr initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
virt KVM: arm/arm64: vgic: Always initialize the group of private IRQs 2019-03-23 20:09:43 +01:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS MAINTAINERS: Add Sasha as a stable branch maintainer 2018-12-01 09:37:25 +01:00
Makefile Linux 4.19.30 2019-03-19 13:12:42 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

README 

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.