From: Vivek Goyal <vgoyal@redhat.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>,
"kexec@lists.infradead.org" <kexec@lists.infradead.org>,
"Eric W. Biederman" <ebiederm@xmission.com>
Subject: Re: How does kdump deal with trampoline allocation?
Date: Mon, 3 Jan 2011 10:31:09 +0530 [thread overview]
Message-ID: <20110103050109.GA3764@redhat.com> (raw)
In-Reply-To: <4D192BC3.8040802@zytor.com>
On Mon, Dec 27, 2010 at 04:13:55PM -0800, H. Peter Anvin wrote:
> On 12/27/2010 04:06 PM, Vivek Goyal wrote:
> > On Mon, Dec 27, 2010 at 12:31:20PM -0800, H. Peter Anvin wrote:
> >> Hi guys,
> >>
> >> I'm planning a major overhaul of the trampoline allocation in x86, and
> >> I'm trying to understand how kdump deals with it. The trampoline has to
> >> be allocated in low memory (< 1 MiB) and obviously that doesn't include
> >> the kdump area at all.
> >
> > Hi Peter,
> >
> > Kdump has the concept of backup area. We backup the contents of first
> > 640KB of physical RAM in kdump reserved area and then allow kdump kernel
> > to use first 640KB of memory. So any trampoline allocation can be done
> > in low memory area without overwritting the contents of first kernel.
> >
>
> OK, that's straightforward. That presumably means that the low 640K is
> marked unused in the memory map that memblock sees during early startup.
Yes, the available memory for second kernel is told to second kernel with
kernel command line option "memmap=", hence it should be visible to
memblock and it should be able to allocate this memory.
Thanks
Vivek
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prev parent reply other threads:[~2011-01-03 5:01 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-27 20:31 How does kdump deal with trampoline allocation? H. Peter Anvin
2010-12-28 0:06 ` Vivek Goyal
2010-12-28 0:13 ` H. Peter Anvin
2010-12-28 7:40 ` Eric W. Biederman
2010-12-28 20:11 ` H. Peter Anvin
2010-12-29 4:13 ` Eric W. Biederman
2010-12-29 6:25 ` H. Peter Anvin
2010-12-29 8:37 ` Eric W. Biederman
2011-01-03 5:01 ` Vivek Goyal [this message]
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