linux-stable/Documentation
Mahesh Salgaonkar a4e92ce8e4 powerpc/fadump: Reservationless firmware assisted dump
One of the primary issues with Firmware Assisted Dump (fadump) on Power
is that it needs a large amount of memory to be reserved. On large
systems with TeraBytes of memory, this reservation can be quite
significant.

In some cases, fadump fails if the memory reserved is insufficient, or
if the reserved memory was DLPAR hot-removed.

In the normal case, post reboot, the preserved memory is filtered to
extract only relevant areas of interest using the makedumpfile tool.
While the tool provides flexibility to determine what needs to be part
of the dump and what memory to filter out, all supported distributions
default this to "Capture only kernel data and nothing else".

We take advantage of this default and the Linux kernel's Contiguous
Memory Allocator (CMA) to fundamentally change the memory reservation
model for fadump.

Instead of setting aside a significant chunk of memory nobody can use,
this patch uses CMA instead, to reserve a significant chunk of memory
that the kernel is prevented from using (due to MIGRATE_CMA), but
applications are free to use it. With this fadump will still be able
to capture all of the kernel memory and most of the user space memory
except the user pages that were present in CMA region.

Essentially, on a P9 LPAR with 2 cores, 8GB RAM and current upstream:
[root@zzxx-yy10 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           7557         193        6822          12         541        6725
Swap:          4095           0        4095

With this patch:
[root@zzxx-yy10 ~]# free -m
              total        used        free      shared  buff/cache   available
Mem:           8133         194        7464          12         475        7338
Swap:          4095           0        4095

Changes made here are completely transparent to how fadump has
traditionally worked.

Thanks to Aneesh Kumar and Anshuman Khandual for helping us understand
CMA and its usage.

TODO:
- Handle case where CMA reservation spans nodes.

Signed-off-by: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>
Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2018-12-21 11:32:49 +11:00
..
ABI LED fixes for 4.20-rc2 2018-11-08 17:49:04 -06:00
accelerators
accounting psi: cgroup support 2018-10-26 16:26:32 -07:00
acpi
admin-guide powerpc/fsl: Add FSL_PPC_BOOK3E as supported arch for nospectre_v2 boot arg 2018-12-20 22:59:03 +11:00
aoe
arm ARM: SoC device tree updates for 4.20 2018-10-29 15:05:20 -07:00
arm64 Documentation/arm64: HugeTLB page implementation 2018-10-10 18:08:36 +01:00
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cma
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driver-model
early-userspace initramfs: move gen_initramfs_list.sh from scripts/ to usr/ 2018-08-22 23:21:44 +09:00
EDID
extcon
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fb This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
features
filesystems This pull request contains updates for UBIFS: 2018-11-04 14:46:04 -08:00
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hid
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iio
infiniband
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kbuild kbuild: remove unused cc-fullversion variable 2018-11-02 00:15:26 +09:00
kdump
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lightnvm
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memory-devices
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misc-devices
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namespaces
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networking Kbuild updates for v4.20 (2nd) 2018-11-03 10:47:33 -07:00
nfc
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openrisc
parisc Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00
PCI pci-v4.20-changes 2018-10-25 06:50:48 -07:00
pcmcia pcmcia: remove long deprecated pcmcia_request_exclusive_irq() function 2018-08-18 12:30:42 -07:00
perf
phy
platform
power This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
powerpc powerpc/fadump: Reservationless firmware assisted dump 2018-12-21 11:32:49 +11:00
pps
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rapidio
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riscv
s390 KVM updates for v4.20 2018-10-25 17:57:35 -07:00
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scsi SCSI misc on 20181024 2018-10-25 07:40:30 -07:00
security Merge branch 'next-keys2' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2018-11-01 15:23:59 -07:00
serial TTY/Serial patches for 4.20-rc1 2018-10-29 10:42:20 -07:00
sh
sound ALSA: doc: Brush up the old writing-an-alsa-driver 2018-10-18 10:30:01 +02:00
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translations This was a moderately busy cycle for docs, with the usual collection of 2018-08-14 14:29:31 -07:00
usb
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watchdog documentation: watchdog: add documentation for armada-37xx-wdt 2018-10-13 15:19:40 +02:00
wimax
x86 x86/mm: Move LDT remap out of KASLR region on 5-level paging 2018-11-06 21:35:11 +01:00
xilinx Documentation: xilinx: Add documentation for eemi APIs 2018-10-09 13:26:05 +02:00
xtensa
.gitignore
atomic_bitops.txt
atomic_t.txt
bt8xxgpio.txt
btmrvl.txt
bus-virt-phys-mapping.txt
Changes
clearing-warn-once.txt
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conf.py This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
cpu-load.txt
cputopology.txt
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
digsig.txt
DMA-API-HOWTO.txt
DMA-API.txt
DMA-attributes.txt
DMA-ISA-LPC.txt
docutils.conf
dontdiff
efi-stub.txt efi_stub: update documentation on dtb= parameter 2018-09-09 14:46:44 -06:00
eisa.txt
flexible-arrays.txt
futex-requeue-pi.txt
gcc-plugins.txt
highuid.txt
hw_random.txt
hwspinlock.txt
index.rst docs: tidy up TOCs and refs to license-rules.rst 2018-08-31 16:50:50 -06:00
Intel-IOMMU.txt
intel_txt.txt
io-mapping.txt
io_ordering.txt
iostats.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
isa.txt
isapnp.txt
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kobject.txt
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kref.txt
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lzo.txt
mailbox.txt
Makefile
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ntb.txt
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padata.txt
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rpmsg.txt
rtc.txt
SAK.txt
sgi-ioc4.txt
siphash.txt
SM501.txt
smsc_ece1099.txt
speculation.txt
static-keys.txt
SubmittingPatches
svga.txt
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tee.txt
this_cpu_ops.txt
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vfio-mediated-device.txt
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xillybus.txt
xz.txt
zorro.txt