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Date: Sat, 31 Oct 2020 15:44:37 +0800
From: Chen Zhou <chenzhou10@...wei.com>
To: <tglx@...utronix.de>, <mingo@...hat.com>, <dyoung@...hat.com>,
<bhe@...hat.com>, <catalin.marinas@....com>, <will@...nel.org>,
<corbet@....net>, <John.P.donnelly@...cle.com>,
<bhsharma@...hat.com>, <prabhakar.pkin@...il.com>
CC: <horms@...ge.net.au>, <robh+dt@...nel.org>, <arnd@...db.de>,
<nsaenzjulienne@...e.de>, <james.morse@....com>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<kexec@...ts.infradead.org>, <linux-doc@...r.kernel.org>,
<chenzhou10@...wei.com>, <xiexiuqi@...wei.com>,
<guohanjun@...wei.com>, <huawei.libin@...wei.com>,
<wangkefeng.wang@...wei.com>,
John Donnelly <John.p.donnelly@...cle.com>
Subject: [PATCH v13 8/8] kdump: update Documentation about crashkernel
For arm64, the behavior of crashkernel=X has been changed, which
tries low allocation in DMA zone or DMA32 zone if CONFIG_ZONE_DMA
is disabled, and fall back to high allocation if it fails.
We can also use "crashkernel=X,high" to select a high region above
DMA zone, which also tries to allocate at least 256M low memory in
DMA zone automatically (or the DMA32 zone if CONFIG_ZONE_DMA is disabled).
"crashkernel=Y,low" can be used to allocate specified size low memory.
So update the Documentation.
Signed-off-by: Chen Zhou <chenzhou10@...wei.com>
Tested-by: John Donnelly <John.p.donnelly@...cle.com>
---
Documentation/admin-guide/kdump/kdump.rst | 23 ++++++++++++++++---
.../admin-guide/kernel-parameters.txt | 12 ++++++++--
2 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index 75a9dd98e76e..bde5f994d185 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -299,7 +299,16 @@ Boot into System Kernel
"crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
- On x86 and x86_64, use "crashkernel=64M@16M".
+ On x86 use "crashkernel=64M@16M".
+
+ On x86_64, use "crashkernel=X" to select a region under 4G first, and
+ fall back to reserve region above 4G. And go for high allocation
+ directly if the required size is too large.
+ We can also use "crashkernel=X,high" to select a region above 4G, which
+ also tries to allocate at least 256M below 4G automatically and
+ "crashkernel=Y,low" can be used to allocate specified size low memory.
+ Use "crashkernel=Y@X" if you really have to reserve memory from specified
+ start address X.
On ppc64, use "crashkernel=128M@32M".
@@ -316,8 +325,16 @@ Boot into System Kernel
kernel will automatically locate the crash kernel image within the
first 512MB of RAM if X is not given.
- On arm64, use "crashkernel=Y[@X]". Note that the start address of
- the kernel, X if explicitly specified, must be aligned to 2MiB (0x200000).
+ On arm64, use "crashkernel=X" to try low allocation in DMA zone (or
+ DMA32 zone if CONFIG_ZONE_DMA is disabled), and fall back to high
+ allocation if it fails.
+ We can also use "crashkernel=X,high" to select a high region above
+ DMA zone, which also tries to allocate at least 256M low memory in
+ DMA zone automatically (or the DMA32 zone if CONFIG_ZONE_DMA is disabled).
+ "crashkernel=Y,low" can be used to allocate specified size low memory.
+ Use "crashkernel=Y@X" if you really have to reserve memory from
+ specified start address X. Note that the start address of the kernel,
+ X if explicitly specified, must be aligned to 2MiB (0x200000).
Load the Dump-capture Kernel
============================
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 526d65d8573a..b2955d9379e8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -738,6 +738,9 @@
[KNL, X86-64] Select a region under 4G first, and
fall back to reserve region above 4G when '@...set'
hasn't been specified.
+ [KNL, arm64] Try low allocation in DMA zone (or DMA32 zone
+ if CONFIG_ZONE_DMA is disabled), fall back to high allocation
+ if it fails when '@...set' hasn't been specified.
See Documentation/admin-guide/kdump/kdump.rst for further details.
crashkernel=range1:size1[,range2:size2,...][@offset]
@@ -754,6 +757,8 @@
Otherwise memory region will be allocated below 4G, if
available.
It will be ignored if crashkernel=X is specified.
+ [KNL, arm64] range in high memory.
+ Allow kernel to allocate physical memory region from top.
crashkernel=size[KMG],low
[KNL, X86-64] range under 4G. When crashkernel=X,high
is passed, kernel could allocate physical memory region
@@ -762,13 +767,16 @@
requires at least 64M+32K low memory, also enough extra
low memory is needed to make sure DMA buffers for 32-bit
devices won't run out. Kernel would try to allocate at
- at least 256M below 4G automatically.
+ least 256M below 4G automatically.
This one let user to specify own low range under 4G
for second kernel instead.
0: to disable low allocation.
It will be ignored when crashkernel=X,high is not used
or memory reserved is below 4G.
-
+ [KNL, arm64] range in low memory.
+ This one let user to specify a low range in DMA zone for
+ crash dump kernel (or the DMA32 zone if CONFIG_ZONE_DMA
+ is disabled).
cryptomgr.notests
[KNL] Disable crypto self-tests
--
2.20.1
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