From: Simon Horman <horms@verge.net.au>
To: Eugene Surovegin <surovegin@google.com>
Cc: kexec-list <kexec@lists.infradead.org>,
linux-kernel@vger.kernel.org, Vivek Goyal <vgoyal@redhat.com>,
Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH] kdump: force page alignment for per-CPU crash notes.
Date: Thu, 1 Mar 2012 10:32:01 +0900 [thread overview]
Message-ID: <20120301013200.GF16483@verge.net.au> (raw)
In-Reply-To: <CANrfoUXd4L2bjBO+L8ZBCkc1dfnZahn39sB25zsrUMqGA5zY5A@mail.gmail.com>
On Wed, Feb 29, 2012 at 05:23:10PM -0800, Eugene Surovegin wrote:
> On Wed, Feb 29, 2012 at 5:18 PM, Simon Horman <horms@verge.net.au> wrote:
>
> > On Wed, Feb 29, 2012 at 09:21:23AM -0800, Eugene Surovegin wrote:
> > > Per-CPU allocations are not guaranteed to be physically contiguous.
> > > However, kdump kernel and user-space code assumes that per-CPU
> > > memory, used for saving CPU registers on crash, is.
> > > This can cause corrupted /proc/vmcore in some cases - the main
> > > symptom being huge ELF note section.
> > >
> > > Force page alignment for note_buf_t to ensure that this assumption holds.
> >
> > Ouch. I'm surprised there is an allocation on crash, perhaps
> > it could at least be done earlier? And am I right in thinking
> > that this change increases the likely hood that the allocation
> > could fail?
> >
>
> I'm not following. This allocation is done on start-up, not on crash.
> If you cannot allocate this much memory on system boot, I'm not sure what
> else you can do on this system....
Sorry, my eyes deceived me. You are correct and I agree.
Is it the case that note_buf_t is never larger than PAGE_SIZE?
If so I your patch looks good to me.
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next prev parent reply other threads:[~2012-03-01 1:32 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-29 17:21 [PATCH] kdump: force page alignment for per-CPU crash notes Eugene Surovegin
2012-03-01 1:18 ` Simon Horman
2012-03-01 1:23 ` Eugene Surovegin
2012-03-01 1:32 ` Simon Horman [this message]
2012-03-01 1:39 ` Eugene Surovegin
2012-03-01 1:51 ` HATAYAMA Daisuke
2012-03-01 1:56 ` Eugene Surovegin
2012-03-01 2:50 ` Simon Horman
2012-03-01 2:53 ` Simon Horman
2012-03-01 15:09 ` Vivek Goyal
2012-03-01 17:04 ` Eugene Surovegin
2012-03-01 18:31 ` Vivek Goyal
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