linux-kernel - [PATCH 0/3 v3] Fix kdump failures with crashkernel=high

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Message-Id: <1433500202-25531-1-git-send-email-joro@8bytes.org>
Date:	Fri,  5 Jun 2015 12:29:59 +0200
From:	Joerg Roedel <joro@...tes.org>
To:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	Dave Young <dyoung@...hat.com>, Baoquan He <bhe@...hat.com>,
	x86@...nel.org, kexec@...ts.infradead.org, joro@...tes.org,
	jroedel@...e.de, linux-kernel@...r.kernel.org
Subject: [PATCH 0/3 v3] Fix kdump failures with crashkernel=high

v2->v3

* Rebased to v4.1-rc6
* Updated changelogs as requested and added outcome of
  previous discussions
* Added more Acked-bys

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 |  7 +++++++
 arch/x86/kernel/setup.c       |  5 ++++-
 lib/swiotlb.c                 | 11 +++++++++--
 3 files changed, 20 insertions(+), 3 deletions(-)

-- 
1.9.1

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