linux-kernel - Re: [PATCH v2 3/5] kdump, documentation: describe craskernel CMA reservation

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Message-ID: <Z8UL8pW84S46Ca/K@MiWiFi-R3L-srv>
Date: Mon, 3 Mar 2025 09:54:58 +0800
From: Baoquan He <bhe@...hat.com>
To: Jiri Bohac <jbohac@...e.cz>
Cc: Vivek Goyal <vgoyal@...hat.com>, Dave Young <dyoung@...hat.com>,
	kexec@...ts.infradead.org, Philipp Rudo <prudo@...hat.com>,
	Donald Dutile <ddutile@...hat.com>, Pingfan Liu <piliu@...hat.com>,
	Tao Liu <ltao@...hat.com>, linux-kernel@...r.kernel.org,
	David Hildenbrand <dhildenb@...hat.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH v2 3/5] kdump, documentation: describe craskernel CMA
 reservation

On 02/20/25 at 05:54pm, Jiri Bohac wrote:
......
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index fb8752b42ec8..ea4d53435515 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -987,6 +987,20 @@
>  			0: to disable low allocation.
>  			It will be ignored when crashkernel=X,high is not used
>  			or memory reserved is below 4G.
> +	crashkernel=size[KMG],cma
> +			[KNL, X86] Reserve additional crash kernel memory from CMA.
> +			This reservation is usable by the first system's userspace,
> +			so this should not be used if dumping of userspace
> +			memory is intended. A standard crashkernel reservation,
> +			as described above, is still needed to hold the crash
> +			kernel and initrd.
> +			This option increases the risk of a kdump failure: DMA
> +			transfers configured by the first kernel may end up
> +			corrupting the second kernel's memory. This reservation
> +			method is intended for systems that can't afford to
> +			sacrifice enough memory for standard crashkernel
> +			reservation and where less reliable kdump is preferrable 
There's trailing whitespace at the end of above line, checkpatch should
be run to check it.

> +			to no kdump at all.
>  
>  	cryptomgr.notests
>  			[KNL] Disable crypto self-tests
> 
> -- 
> Jiri Bohac <jbohac@...e.cz>
> SUSE Labs, Prague, Czechia
>