linux-kernel - Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel low memory reserving failed

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Date:	Mon, 27 Jul 2015 16:41:24 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Baoquan He <bhe@...hat.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com, bp@...e.de,
	akpm@...ux-foundation.org, jkosina@...e.cz, vgoyal@...hat.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Do not reserve crashkernel high memory if crashkernel
 low memory reserving failed

Hi Baoquan,

thanks for the fix!

On Sun, Jul 19, 2015 at 10:53:20PM +0800, Baoquan He wrote:
> People reported that when allocating crashkernel memory using
> ",high" and ",low" syntax, there were cases where the reservation
> of the "high" portion succeeds, but the reservation of the "low"
> portion fails. Then kexec can load kdump kernel successfully, but
> the boot of kdump kernel fails as there's no low memory. This is
> because allocation of low memory for kdump kernel can fail on large
> systems for reasons. E.g it could be manually specified crashkernel
> low memory is too large to find in memblock region.
> 
> In this patch add return value for reserve_crashkernel_low. Then put
> the crashkernel low memory reserving earlier, just between finding
> the crashkernel high memory region and reserving crashkernel high
> memory. Then if crashkernel low memory reserving failed we do not
> reserve crashkernel high memory but return immediately. Users can
> take measures when they found kdump kernel cann't be loaded
> successfully.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  arch/x86/kernel/setup.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)

Reviewed-by: Joerg Roedel <jroedel@...e.de>

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