From: Vivek Goyal <vgoyal@redhat.com>
To: Eugene Surovegin <surovegin@google.com>
Cc: kexec-list <kexec@lists.infradead.org>,
linux-kernel@vger.kernel.org,
Eric Biederman <ebiederm@xmission.com>
Subject: Re: [PATCH] kdump: force page alignment for per-CPU crash notes.
Date: Thu, 1 Mar 2012 13:31:15 -0500 [thread overview]
Message-ID: <20120301183115.GE13533@redhat.com> (raw)
In-Reply-To: <CANrfoUVMP5hPfm2R=C9eszS728YccKyWokUAa5Q5KN36+W83bg@mail.gmail.com>
On Thu, Mar 01, 2012 at 09:04:32AM -0800, Eugene Surovegin wrote:
> On Thu, Mar 1, 2012 at 7:09 AM, Vivek Goyal <vgoyal@redhat.com> 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.
> >>
> >
> > Hi Eugene,
> >
> > Where do we make assumption that crash_notes address is page aligned?
>
> I never said that. I said that assumption was that note chunks were
> physically contiguous.
>
> [snip]
>
> > Are you referring to the fact that note could be stored on two different
> > physical pages and then kexec-tools does not know about the physical
> > address of second page, hence second kernel does not know about it
> > and we never read that data. That sounds like a problem.
>
> Yes. This is exactly what happens in some cases.
Ok. Thanks for clarifying. Patch looks good to me.
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Vivek
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WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Eugene Surovegin <surovegin@google.com>
Cc: linux-kernel@vger.kernel.org,
Eric Biederman <ebiederm@xmission.com>,
kexec-list <kexec@lists.infradead.org>
Subject: Re: [PATCH] kdump: force page alignment for per-CPU crash notes.
Date: Thu, 1 Mar 2012 13:31:15 -0500 [thread overview]
Message-ID: <20120301183115.GE13533@redhat.com> (raw)
In-Reply-To: <CANrfoUVMP5hPfm2R=C9eszS728YccKyWokUAa5Q5KN36+W83bg@mail.gmail.com>
On Thu, Mar 01, 2012 at 09:04:32AM -0800, Eugene Surovegin wrote:
> On Thu, Mar 1, 2012 at 7:09 AM, Vivek Goyal <vgoyal@redhat.com> 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.
> >>
> >
> > Hi Eugene,
> >
> > Where do we make assumption that crash_notes address is page aligned?
>
> I never said that. I said that assumption was that note chunks were
> physically contiguous.
>
> [snip]
>
> > Are you referring to the fact that note could be stored on two different
> > physical pages and then kexec-tools does not know about the physical
> > address of second page, hence second kernel does not know about it
> > and we never read that data. That sounds like a problem.
>
> Yes. This is exactly what happens in some cases.
Ok. Thanks for clarifying. Patch looks good to me.
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Vivek
next prev parent reply other threads:[~2012-03-01 18:56 UTC|newest]
Thread overview: 23+ 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
2012-02-29 17:21 ` Eugene Surovegin
2012-03-01 1:18 ` Simon Horman
2012-03-01 1:18 ` Simon Horman
2012-03-01 1:23 ` Eugene Surovegin
2012-03-01 1:32 ` Simon Horman
2012-03-01 1:32 ` Simon Horman
2012-03-01 1:39 ` Eugene Surovegin
2012-03-01 1:39 ` Eugene Surovegin
2012-03-01 1:51 ` HATAYAMA Daisuke
2012-03-01 1:51 ` HATAYAMA Daisuke
2012-03-01 1:56 ` Eugene Surovegin
2012-03-01 1:56 ` Eugene Surovegin
2012-03-01 2:50 ` Simon Horman
2012-03-01 2:50 ` Simon Horman
2012-03-01 2:53 ` Simon Horman
2012-03-01 2:53 ` Simon Horman
2012-03-01 15:09 ` Vivek Goyal
2012-03-01 15:09 ` Vivek Goyal
2012-03-01 17:04 ` Eugene Surovegin
2012-03-01 17:04 ` Eugene Surovegin
2012-03-01 18:31 ` Vivek Goyal [this message]
2012-03-01 18:31 ` Vivek Goyal
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