OpenE2K
/
linux
6
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity
890,284 Commits 4 Branches 0 Tags 2 GiB
C 97.7%
Assembly 1.3%
Makefile 0.4%
Shell 0.3%
Python 0.1%
Other 0.1%
Go to file
Baoquan He 7ad300800c mm_zone: add function to check if managed dma zone exists 
commit 62b3107073646e0946bd97ff926832bafb846d17 upstream.

Patch series "Handle warning of allocation failure on DMA zone w/o
managed pages", v4.

**Problem observed:
On x86_64, when crash is triggered and entering into kdump kernel, page
allocation failure can always be seen.

 ---------------------------------
 DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
 swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 0 PID: 1 Comm: swapper/0
 Call Trace:
  dump_stack+0x7f/0xa1
  warn_alloc.cold+0x72/0xd6
  ......
  __alloc_pages+0x24d/0x2c0
  ......
  dma_atomic_pool_init+0xdb/0x176
  do_one_initcall+0x67/0x320
  ? rcu_read_lock_sched_held+0x3f/0x80
  kernel_init_freeable+0x290/0x2dc
  ? rest_init+0x24f/0x24f
  kernel_init+0xa/0x111
  ret_from_fork+0x22/0x30
 Mem-Info:
 ------------------------------------

***Root cause:
In the current kernel, it assumes that DMA zone must have managed pages
and try to request pages if CONFIG_ZONE_DMA is enabled. While this is not
always true. E.g in kdump kernel of x86_64, only low 1M is presented and
locked down at very early stage of boot, so that this low 1M won't be
added into buddy allocator to become managed pages of DMA zone. This
exception will always cause page allocation failure if page is requested
from DMA zone.

***Investigation:
This failure happens since below commit merged into linus's tree.
  1a6a9044b967 x86/setup: Remove CONFIG_X86_RESERVE_LOW and reservelow= options
  23721c8e92f7 x86/crash: Remove crash_reserve_low_1M()
  f1d4d47c5851 x86/setup: Always reserve the first 1M of RAM
  7c321eb2b8 x86/kdump: Remove the backup region handling
  6f599d8423 x86/kdump: Always reserve the low 1M when the crashkernel option is specified

Before them, on x86_64, the low 640K area will be reused by kdump kernel.
So in kdump kernel, the content of low 640K area is copied into a backup
region for dumping before jumping into kdump. Then except of those firmware
reserved region in [0, 640K], the left area will be added into buddy
allocator to become available managed pages of DMA zone.

However, after above commits applied, in kdump kernel of x86_64, the low
1M is reserved by memblock, but not released to buddy allocator. So any
later page allocation requested from DMA zone will fail.

At the beginning, if crashkernel is reserved, the low 1M need be locked
down because AMD SME encrypts memory making the old backup region
mechanims impossible when switching into kdump kernel.

Later, it was also observed that there are BIOSes corrupting memory
under 1M. To solve this, in commit f1d4d47c5851, the entire region of
low 1M is always reserved after the real mode trampoline is allocated.

Besides, recently, Intel engineer mentioned their TDX (Trusted domain
extensions) which is under development in kernel also needs to lock down
the low 1M. So we can't simply revert above commits to fix the page allocation
failure from DMA zone as someone suggested.

***Solution:
Currently, only DMA atomic pool and dma-kmalloc will initialize and
request page allocation with GFP_DMA during bootup.

So only initializ DMA atomic pool when DMA zone has available managed
pages, otherwise just skip the initialization.

For dma-kmalloc(), for the time being, let's mute the warning of
allocation failure if requesting pages from DMA zone while no manged
pages.  Meanwhile, change code to use dma_alloc_xx/dma_map_xx API to
replace kmalloc(GFP_DMA), or do not use GFP_DMA when calling kmalloc() if
not necessary.  Christoph is posting patches to fix those under
drivers/scsi/.  Finally, we can remove the need of dma-kmalloc() as people
suggested.

This patch (of 3):

In some places of the current kernel, it assumes that dma zone must have
managed pages if CONFIG_ZONE_DMA is enabled.  While this is not always
true.  E.g in kdump kernel of x86_64, only low 1M is presented and locked
down at very early stage of boot, so that there's no managed pages at all
in DMA zone.  This exception will always cause page allocation failure if
page is requested from DMA zone.

Here add function has_managed_dma() and the relevant helper functions to
check if there's DMA zone with managed pages.  It will be used in later
patches.

Link: https://lkml.kernel.org/r/20211223094435.248523-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20211223094435.248523-2-bhe@redhat.com
Fixes: 6f599d8423 ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: John Donnelly  <john.p.donnelly@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Robin Murphy <robin.murphy@arm.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2022-01-27 09:19:28 +01:00
Documentation Input: i8042 - add deferred probe support 2022-01-05 12:37:43 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
arch x86/gpu: Reserve stolen memory for first integrated Intel GPU 2022-01-27 09:19:26 +01:00
block block: fix ioprio_get(IOPRIO_WHO_PGRP) vs setuid(2) 2021-12-14 14:49:02 +01:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-17 09:48:40 +01:00
drivers PCI: Add function 1 DMA alias quirk for Marvell 88SE9125 SATA controller 2022-01-27 09:19:28 +01:00
fs f2fs: fix to do sanity check in is_alive() 2022-01-27 09:19:26 +01:00
include mm_zone: add function to check if managed dma zone exists 2022-01-27 09:19:28 +01:00
init kbuild: add CONFIG_LD_IS_LLD 2021-06-30 08:47:44 -04:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel perf: Protect perf_guest_cbs with RCU 2022-01-20 09:19:18 +01:00
lib siphash: use _unaligned version by default 2021-12-08 09:01:12 +01:00
mm mm_zone: add function to check if managed dma zone exists 2022-01-27 09:19:28 +01:00
net nfc: llcp: fix NULL error pointer dereference on sendmsg() after failed bind() 2022-01-27 09:19:26 +01:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts recordmcount.pl: fix typo in s390 mcount regex 2022-01-05 12:37:44 +01:00
security selinux: initialize proto variable in selinux_ip_postroute_compat() 2022-01-05 12:37:44 +01:00
sound ALSA: hda/realtek - Fix silent output on Gigabyte X570 Aorus Master after reboot from Windows 2022-01-20 09:19:18 +01:00
tools tools/nolibc: fix incorrect truncation of exit code 2022-01-27 09:19:27 +01:00
usr initramfs: restore default compression behavior 2020-04-08 09:08:38 +02:00
virt KVM: do not shrink halt_poll_ns below grow_start 2021-10-09 14:39:50 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
…
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes
…
.gitignore Modules updates for v5.4 2019-09-22 10:34:46 -07:00
.mailmap ARM: SoC fixes 2019-11-10 13:41:59 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS MAINTAINERS: Remove Simon as Renesas SoC Co-Maintainer 2019-10-10 08:12:51 -07:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2020-08-26 10:40:46 +02:00
Makefile Linux 5.4.173 2022-01-20 09:19:19 +01:00
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.