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

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Date:	Fri, 28 Nov 2014 12:29:06 +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>, Joerg Roedel <joro@...tes.org>
Subject: [PATCH 0/3] Fix kdump failures with crashkernel=high

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

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