diff mbox series

[v20,5/5] kdump: update Documentation about crashkernel

Message ID 20220124084708.683-6-thunder.leizhen@huawei.com (mailing list archive)
State New, archived
Headers show
Series support reserving crashkernel above 4G on arm64 kdump | expand

Commit Message

Leizhen (ThunderTown) Jan. 24, 2022, 8:47 a.m. UTC 
From: Chen Zhou <chenzhou10@huawei.com>

For arm64, the behavior of crashkernel=X has been changed, which
tries low allocation in DMA zone 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 and "crashkernel=Y,low" can be used to allocate
specified size low memory.

So update the Documentation.

Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
 Documentation/admin-guide/kdump/kdump.rst       | 11 +++++++++--
 Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
 2 files changed, 18 insertions(+), 4 deletions(-)

Comments

John Donnelly Jan. 26, 2022, 3:19 p.m. UTC | #1 
On 1/24/22 2:47 AM, Zhen Lei wrote:
> From: Chen Zhou <chenzhou10@huawei.com>
> 
> For arm64, the behavior of crashkernel=X has been changed, which
> tries low allocation in DMA zone 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 and "crashkernel=Y,low" can be used to allocate
> specified size low memory.
> 
> So update the Documentation.
> 
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>

Acked-by: John Donnelly  <john.p.donnelly@oracle.com>

> ---
>   Documentation/admin-guide/kdump/kdump.rst       | 11 +++++++++--
>   Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
>   2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index cb30ca3df27c9b2..d4c287044be0c70 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -361,8 +361,15 @@ 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 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.
> +   "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 f5a27f067db9ed9..65780c2ca830be0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -792,6 +792,9 @@
>   			[KNL, X86-64] Select a region under 4G first, and
>   			fall back to reserve region above 4G when '@offset'
>   			hasn't been specified.
> +			[KNL, ARM64] Try low allocation in DMA zone and fall back
> +			to high allocation if it fails when '@offset' hasn't been
> +			specified.
>   			See Documentation/admin-guide/kdump/kdump.rst for further details.
>   
>   	crashkernel=range1:size1[,range2:size2,...][@offset]
> @@ -808,6 +811,8 @@
>   			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
> @@ -816,13 +821,15 @@
>   			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.
>   	cryptomgr.notests
>   			[KNL] Disable crypto self-tests
>
Baoquan He Feb. 21, 2022, 3:48 a.m. UTC | #2 
On 01/24/22 at 04:47pm, Zhen Lei wrote:
> From: Chen Zhou <chenzhou10@huawei.com>
> 
> For arm64, the behavior of crashkernel=X has been changed, which
> tries low allocation in DMA zone 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 and "crashkernel=Y,low" can be used to allocate
> specified size low memory.
> 
> So update the Documentation.
> 
> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> ---
>  Documentation/admin-guide/kdump/kdump.rst       | 11 +++++++++--
>  Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
>  2 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
> index cb30ca3df27c9b2..d4c287044be0c70 100644
> --- a/Documentation/admin-guide/kdump/kdump.rst
> +++ b/Documentation/admin-guide/kdump/kdump.rst
> @@ -361,8 +361,15 @@ 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 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.
> +   "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).

Hmm, we may not need the details related to crashkernel,high|low in this
section. This just gives examples of basic configation for each ARCH.
The detailed configuration of all crashkernel setting can be found in
"crashkernel syntax" section, I don't think arm64 is so special to need
a specific one.

>  
>  Load the Dump-capture Kernel
>  ============================
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f5a27f067db9ed9..65780c2ca830be0 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -792,6 +792,9 @@
>  			[KNL, X86-64] Select a region under 4G first, and
>  			fall back to reserve region above 4G when '@offset'
>  			hasn't been specified.
> +			[KNL, ARM64] Try low allocation in DMA zone and fall back
> +			to high allocation if it fails when '@offset' hasn't been
> +			specified.
>  			See Documentation/admin-guide/kdump/kdump.rst for further details.

How about add ARM64 like below to avoid redundant words?
  			[KNL, X86-64, ARM64] Select a region under 4G first, and
  			fall back to reserve region above 4G when '@offset'
  			hasn't been specified.

>  
>  	crashkernel=range1:size1[,range2:size2,...][@offset]
> @@ -808,6 +811,8 @@
>  			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.

Ditto, please don't add redundent words if it's similar to x86_64
handling.

>  	crashkernel=size[KMG],low
>  			[KNL, X86-64] range under 4G. When crashkernel=X,high
>  			is passed, kernel could allocate physical memory region
> @@ -816,13 +821,15 @@
>  			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.

Ditto.

>  	cryptomgr.notests
>  			[KNL] Disable crypto self-tests
>  
> -- 
> 2.25.1
>
Leizhen (ThunderTown) Feb. 21, 2022, 6:38 a.m. UTC | #3 
On 2022/2/21 11:48, Baoquan He wrote:
> On 01/24/22 at 04:47pm, Zhen Lei wrote:
>> From: Chen Zhou <chenzhou10@huawei.com>
>>
>> For arm64, the behavior of crashkernel=X has been changed, which
>> tries low allocation in DMA zone 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 and "crashkernel=Y,low" can be used to allocate
>> specified size low memory.
>>
>> So update the Documentation.
>>
>> Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>>  Documentation/admin-guide/kdump/kdump.rst       | 11 +++++++++--
>>  Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++--
>>  2 files changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
>> index cb30ca3df27c9b2..d4c287044be0c70 100644
>> --- a/Documentation/admin-guide/kdump/kdump.rst
>> +++ b/Documentation/admin-guide/kdump/kdump.rst
>> @@ -361,8 +361,15 @@ 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 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.
>> +   "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).
> 
> Hmm, we may not need the details related to crashkernel,high|low in this
> section. This just gives examples of basic configation for each ARCH.
> The detailed configuration of all crashkernel setting can be found in
> "crashkernel syntax" section, I don't think arm64 is so special to need
> a specific one.
> 
>>  
>>  Load the Dump-capture Kernel
>>  ============================
>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>> index f5a27f067db9ed9..65780c2ca830be0 100644
>> --- a/Documentation/admin-guide/kernel-parameters.txt
>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>> @@ -792,6 +792,9 @@
>>  			[KNL, X86-64] Select a region under 4G first, and
>>  			fall back to reserve region above 4G when '@offset'
>>  			hasn't been specified.
>> +			[KNL, ARM64] Try low allocation in DMA zone and fall back
>> +			to high allocation if it fails when '@offset' hasn't been
>> +			specified.
>>  			See Documentation/admin-guide/kdump/kdump.rst for further details.
> 
> How about add ARM64 like below to avoid redundant words?
>   			[KNL, X86-64, ARM64] Select a region under 4G first, and
>   			fall back to reserve region above 4G when '@offset'
>   			hasn't been specified.

I agree very much, and I think that's the right thing to do. Thanks.

I wanted to do the same before, just wasn't sure if the format was correct. I just
looked at the other descriptions in kernel-parameters.txt and found that there are
many precedents.

"movablecore=    [KNL,X86,IA-64,PPC]"

> 
>>  
>>  	crashkernel=range1:size1[,range2:size2,...][@offset]
>> @@ -808,6 +811,8 @@
>>  			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.
> 
> Ditto, please don't add redundent words if it's similar to x86_64
> handling.
> 
>>  	crashkernel=size[KMG],low
>>  			[KNL, X86-64] range under 4G. When crashkernel=X,high
>>  			is passed, kernel could allocate physical memory region
>> @@ -816,13 +821,15 @@
>>  			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.
> 
> Ditto.
> 
>>  	cryptomgr.notests
>>  			[KNL] Disable crypto self-tests
>>  
>> -- 
>> 2.25.1
>>
> 
> .
>
diff mbox series

Patch

diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst
index cb30ca3df27c9b2..d4c287044be0c70 100644
--- a/Documentation/admin-guide/kdump/kdump.rst
+++ b/Documentation/admin-guide/kdump/kdump.rst
@@ -361,8 +361,15 @@  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 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.
+   "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 f5a27f067db9ed9..65780c2ca830be0 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -792,6 +792,9 @@ 
 			[KNL, X86-64] Select a region under 4G first, and
 			fall back to reserve region above 4G when '@offset'
 			hasn't been specified.
+			[KNL, ARM64] Try low allocation in DMA zone and fall back
+			to high allocation if it fails when '@offset' hasn't been
+			specified.
 			See Documentation/admin-guide/kdump/kdump.rst for further details.
 
 	crashkernel=range1:size1[,range2:size2,...][@offset]
@@ -808,6 +811,8 @@ 
 			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
@@ -816,13 +821,15 @@ 
 			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.
 	cryptomgr.notests
 			[KNL] Disable crypto self-tests