linux-kernel - Re: [PATCH 0/3 v2] Fix kdump failures with crashkernel=high

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Date:	Wed, 14 Jan 2015 14:35:21 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Joerg Roedel <jroedel@...e.de>
Subject: Re: [PATCH 0/3 v2] Fix kdump failures with crashkernel=high

Ping.

On Tue, Jan 06, 2015 at 03:51:11PM +0100, Joerg Roedel wrote:
> v1->v2:
> 
> * Updated comments based on feedback from Konrad
> * Added Acked-bys
> * Rebased to v3.19-rc3
> 
> Hi,
> 
> here is a patch-set to fix failed kdump kernel boots when
> the systems was booted with crashkernel=X,high. On those
> systems the kernel allocates only 72MiB of low-memory for
> DMA buffers, which showed to be too low on some systems.
> 
> The problem is that 64MiB of the low-memory is allocated by
> swiotlb, leaving 8MB for the page-allocator. But swiotlb
> tries to allocate DMA memory from the page-allocator first,
> which fails pretty fast in the boot sequence, causing
> warnings. This patch-set removes these warnings.
> 
> But even the 64MiB for swiotlb are eaten up on some systems,
> so that the default of low-memory allocated for the
> crash-kernel is increase from 72MB to 256MB (only changing
> the defaults, can still be overwritten by crashkernel=X,low).
> 
> This number comes from experiments on the affected systems,
> 128MiB low-memory was still not enough there, thus I set the
> value to 256MiB to fix the issues.
> 
> Any feedback appreciated.
> 
> Thanks,
> 
> 	Joerg
> 
> Joerg Roedel (3):
>   swiotlb: Warn on allocation failure in swiotlb_alloc_coherent
>   x86, swiotlb: Try coherent allocations with __GFP_NOWARN
>   x86, crash: Allocate enough low-mem when crashkernel=high
> 
>  arch/x86/kernel/pci-swiotlb.c |  8 ++++++++
>  arch/x86/kernel/setup.c       |  5 ++++-
>  lib/swiotlb.c                 | 11 +++++++++--
>  3 files changed, 21 insertions(+), 3 deletions(-)
> 
> -- 
> 1.9.1
> 
> Joerg Roedel (3):
>   swiotlb: Warn on allocation failure in swiotlb_alloc_coherent
>   x86, swiotlb: Try coherent allocations with __GFP_NOWARN
>   x86, crash: Allocate enough low-mem when crashkernel=high
> 
>  arch/x86/kernel/pci-swiotlb.c |  8 ++++++++
>  arch/x86/kernel/setup.c       |  5 ++++-
>  lib/swiotlb.c                 | 11 +++++++++--
>  3 files changed, 21 insertions(+), 3 deletions(-)
> 
> -- 
> 1.9.1
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