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Russell King a037ebbe72 PCI: Dynamically map ECAM regions 
[ Upstream commit 8fe55ef233 ]

Attempting to boot 32-bit ARM kernels under QEMU's 3.x virt models fails
when we have more than 512M of RAM in the model as we run out of vmalloc
space for the PCI ECAM regions. This failure will be silent when running
libvirt, as the console in that situation is a PCI device.

In this configuration, the kernel maps the whole ECAM, which QEMU sets up
for 256 buses, even when maybe only seven buses are in use.  Each bus uses
1M of ECAM space, and ioremap() adds an additional guard page between
allocations. The kernel vmap allocator will align these regions to 512K,
resulting in each mapping eating 1.5M of vmalloc space. This means we need
384M of vmalloc space just to map all of these, which is very wasteful of
resources.

Fix this by only mapping the ECAM for buses we are going to be using.  In
my setups, this is around seven buses in most guests, which is 10.5M of
vmalloc space - way smaller than the 384M that would otherwise be required.
This also means that the kernel can boot without forcing extra RAM into
highmem with the vmalloc= argument, or decreasing the virtual RAM available
to the guest.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/E1lhCAV-0002yb-50@rmk-PC.armlinux.org.uk
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2021-07-20 16:00:24 +02:00
arch ARM: 9087/1: kprobes: test-thumb: fix for LLVM_IAS=1 2021-07-20 16:00:23 +02:00
block partitions: msdos: fix one-byte get_unaligned() 2021-07-20 16:00:13 +02:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto crypto: sm2 - fix a memory leak in sm2 2021-07-14 17:06:44 +02:00
Documentation power: supply: max17040: Do not enforce (incorrect) interrupt trigger type 2021-07-20 16:00:23 +02:00
drivers PCI: Dynamically map ECAM regions 2021-07-20 16:00:24 +02:00
fs NFSv4: Fix delegation return in cases where we have to retry 2021-07-20 16:00:23 +02:00
include PCI: Dynamically map ECAM regions 2021-07-20 16:00:24 +02:00
init sched/core: Initialize the idle task with preemption disabled 2021-07-14 17:06:21 +02:00
ipc ipc/mqueue, msg, sem: avoid relying on a stack reference past its expiry 2021-05-22 15:09:07 -10:00
kernel rcu: Reject RCU_LOCKDEP_WARN() false positives 2021-07-20 16:00:12 +02:00
lib lib/decompress_unlz4.c: correctly handle zero-padding around initrds. 2021-07-20 16:00:22 +02:00
LICENSES LICENSES: Add the CC-BY-4.0 license 2020-12-08 10:33:27 -07:00
mm mm/hugetlb: fix refs calculation from unaligned @vaddr 2021-07-20 16:00:10 +02:00
net net: bridge: multicast: fix MRD advertisement router port marking race 2021-07-20 16:00:11 +02:00
samples samples/bpf: Fix the error return code of xdp_redirect's main() 2021-07-14 17:07:08 +02:00
scripts kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_<obj> := n' 2021-07-14 17:06:40 +02:00
security smackfs: restrict bytes count in smk_set_cipso() 2021-07-19 10:04:55 +02:00
sound ALSA: firewire-motu: fix detection for S/PDIF source on optical interface in v2 protocol 2021-07-20 16:00:21 +02:00
tools selftests/powerpc: Fix "no_handler" EBB selftest 2021-07-20 16:00:18 +02:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio 2021-07-20 16:00:08 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Marek's other e-mail address and identity without diacritics 2021-06-24 19:40:54 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge branch 'akpm' (patches from Andrew) 2021-06-25 11:05:03 -07:00
Makefile Linux 5.13.3 2021-07-19 10:04:55 +02:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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.

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.