Commit 94fb9334 authored Jun 10, 2015 by Joerg Roedel Committed by Ingo Molnar Jun 11, 2015

x86/crash: Allocate enough low memory when crashkernel=high



When the crash kernel is loaded above 4GiB in memory, the
first kernel allocates only 72MiB of low-memory for the DMA
requirements of the second kernel. On systems with many
devices this is not enough and causes device driver
initialization errors and failed crash dumps. Testing by
SUSE and Redhat has shown that 256MiB is a good default
value for now and the discussion has lead to this value as
well. So set this default value to 256MiB to make sure there
is enough memory available for DMA.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
[ Reflow comment. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jörg Rödel <joro@8bytes.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: kexec@lists.infradead.org
Link: http://lkml.kernel.org/r/1433500202-25531-4-git-send-email-joro@8bytes.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 186dfc9d

arch/x86/kernel/setup.c

+7 −5

Original line number	Diff line number	Diff line
		@@ -531,12 +531,14 @@ static void __init reserve_crashkernel_low(void)
		if (ret != 0) {
		/*
		* two parts from lib/swiotlb.c:
		* swiotlb size: user specified with swiotlb= or default.
		* swiotlb overflow buffer: now is hardcoded to 32k.
		* We round it to 8M for other buffers that
		* may need to stay low too.
		* -swiotlb size: user-specified with swiotlb= or default.
		*
		* -swiotlb overflow buffer: now hardcoded to 32k. We round it
		* to 8M for other buffers that may need to stay low too. Also
		* make sure we allocate enough extra low memory so that we
		* don't run out of DMA buffers for 32-bit devices.
		*/
		low_size = swiotlb_size_or_default() + (8UL<<20);
		low_size = max(swiotlb_size_or_default() + (8UL<<20), 256UL<<20);
		auto_set = true;
		} else {
		/* passed with crashkernel=0,low ? */

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