From: Simon Horman <horms@verge.net.au>
To: Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org
Subject: Re: [PATCH] kexec/fs2dt: fix endianess conversion
Date: Thu, 17 Oct 2013 10:44:01 +0900 [thread overview]
Message-ID: <20131017014401.GM21728@verge.net.au> (raw)
In-Reply-To: <20131017014253.GL21728@verge.net.au>
On Thu, Oct 17, 2013 at 10:42:53AM +0900, Simon Horman wrote:
> On Wed, Oct 16, 2013 at 11:33:43AM +0200, Laurent Dufour wrote:
> > On 16/10/2013 09:28, Simon Horman wrote:
> > > On Tue, Oct 15, 2013 at 07:05:28PM +0200, Laurent Dufour wrote:
> > >> While reviewing fs2dt.c in the common kexec directory, in order to use it to
> > >> support little endian ppc64 architecture, I found some endianess
> > >> conversion's issues.
> > >>
> > >> In dt_reserve, dt_base is a pointer and thus should not be converted.
> > >>
> > >> In checkprop, values read from the device tree are big endian encoded and
> > >> should be converted if CPU is running in little endian mode.
> > >>
> > >> In add_dyn_reconf_usable_mem_property__, fix extraneous endianess conversion
> > >> of rlen which should be natively used to increase the dt pointer.
> > >
> > > These changes seem logical to me.
> > >
> > > However, I'm unsure how the code might have worked as-is.
> > > In particular I'm pretty sure ARM was running in little endian
> > > mode when I worked on DT support for it. Perhaps these code
> > > paths were not executed. Or the errors cancelled themselves out somehow?
> >
> > I've to admit that I don't know how this has worked for ARM.
> > I run this patch with a set of change I'm working on to support PPC64
> > little endian architecture. My tests were done with kexec-tools built in
> > little endian mode, using this fs2dt.c file and I need this fix to build
> > a valid device tree.
> >
> > The fix is dt_reserve is hit unless the device tree is large enough. I
> > had to reduce INIT_TREE_WORDS to hit it.
> >
> > I think the ones in checkprop, add_dyn_reconf_usable_mem_property__ are
> > Power specific since RTAS and 'ibm,dynamic-memory' are required to hit them.
> >
> > This may explain why this issue are not seen in ARM mode.
>
> Perhaps, its a bit of a mystery.
> I think that I will apply your change as it does seem to be correct.
And I have. It should appear on kernel.org shortly.
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prev parent reply other threads:[~2013-10-17 1:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-15 17:05 [PATCH] kexec/fs2dt: fix endianess conversion Laurent Dufour
2013-10-16 7:28 ` Simon Horman
2013-10-16 9:33 ` Laurent Dufour
2013-10-17 1:42 ` Simon Horman
2013-10-17 1:44 ` Simon Horman [this message]
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